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Title: Full As Level Biology Notes
Description: Full As Level Biology notes for AQA
Description: Full As Level Biology notes for AQA
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Biology revision
AQA As Level
Contents
Monomers & Polymers
•
Cells 3
...
1
Monomers & Polymers
Key Terms
-
Monomer - A small basic molecular unit i
...
Amino Acid & Monosaccharides
Polymer - A large complex molecule made of Monomer chains
Monosaccharides - Carbohydrate Monomer - Fructose or Glucose
Disaccharides - Molecule made of 2 monosaccharides - Sucrose, Maltose
Polysaccharides - Carbohydrate formed from 3 + monosaccharides
Nucleotides - Polynucleotide monomer - Eg Thymine in DNA
Polynucleotides - Long strand of nucleotides - make up DNA double helix
Amino Acid - Protein Monomer
Polypeptide - Molecule made of 2+ amino acids
Reducing Sugar - Most monosaccharides + some disaccharides - Reduces the ions in
Benedict's solution
Non-Reducing Sugar - Monosaccharides + Disaccharides - do not reduce Benedict’s
solution
Hydrolysis Reaction - Reaction uses water molecules to break bonds between
molecules
...
Monomers & Polymers
Key Terms
•
•
•
•
•
•
•
•
•
•
•
Hydrophilic - Attraction to water - Glycerol and Phosphate group molecules in Lipids
Hydrophobic - Repulsion of water - Fatty acids in lipids
Saturated Fatty acid - Hydrocarbon chain with no double carbon bonds - Saturated
in Hydrogen atoms - straight chain
Unsaturated Fatty acid - Hydrocarbon chain with double carbon bonds - not 2
hydrogen to every carbon - kinked chain
Ester bond - The chemical bond which joins a Glycerol molecule to fatty acids - Lipids
Glycosidic Bond - The chemical bond which joins monosaccharides together Carbohydrates
Peptide Bond - The chemical bond which joins amino acids together - Proteins
Microfibrils - Fibres formed by Hydrogen bonds - give cellulose its rigidity
Triglyceride - Lipid with 1 Glycerol and 3 Fatty acid molecules
Phospholipid - Lipid with 1 Glycerol, 2 fatty acid molecules and 1 Phosphate group
Fatty acid - Hydrocarbon tail which is chemically bonded to a Glycerol molecules in
Lipids
Monomers & Polymers
Key Terms
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•
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•
•
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Benedict’s Test - Test for reducing and non-reducing sugars
Iodine Test - Test for starch
Emulsion Test - Test for lipids
Biuret test - Test for proteins
Enzymes - Proteins with a tertiary shape which catalyse reaction
DNA - Deoxyribonucleic acid - Nucleic acid - Contains the genetic information for all cells
...
Genetic continuity - Ensures parent and daughter organisms have identical genes
Organic Nitrogenous Base - Adenine, Thymine, Cytosine, Guanine - Bases of DNA
Sugar - Phosphate Backbone - The alternating sugar ad phosphate groups joined together in a
polynucleotide chains
...
Semi - conservative - Describes DNA replication structure - Half original strand Half new nucleotide strand
DNA Helicase - The enzyme which catalysis the hydrolysis reaction between DNA nucleotides - breaks
hydrogen bonds - Strands unzip
DNA Polymerase - The enzyme which catalyses the condensation reaction between nucleotide bases forms hydrogen bonds
Monomers & Polymers
Key Terms
•
•
•
•
•
•
•
•
•
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Adenosine Triphosphate - ATP - Produced in Mitochondria for energy - Made
from glucose molecules
Adenosine Diphosphate - ADP - Produced by the hydrolysis of ATP
ATP Synthase - The enzyme which catalyses the condensation reaction for the
synthesis of ATP
ATP Hydrolase - The enzyme which catalyses the hydrolysis reaction in the
breakdown of ATP
...
Coupling - When ATP hydrolysis is paired ‘Coupled’ to an energy-requiring reaction
- Allows energy to be used directly rather than wasted as heat
...
Monomers & Polymers
Key Terms
•
•
•
•
•
Solvent - How water surrounds an ionic substance, pulling out ions - causing
substance to dissolve
...
H2O - relatively high - H Bonds absorb lots of energy before breaking + allowing
water to break
...
Cohesive - H Bonds cause H2O molecules to stick together
...
•
•
Suggests they all stem from one / few common
ancestors
...
•
Proves plantas and animals have the same common
ancestors
...
Polymers are large number of monomers joined
together
...
•
Monomers - SMALL + SIMPLE
•
Polymers - LONGER + COMPLEX
Monomers
Monosacharides
Amino Acids
Nucleotides
Polymers
Carbohydtraes
Proteins
DNA
Condensation Reaction
Condensation Reaction - Forms polymers from monomers
Water molecule is eliminated
Chemical bond formed
- Glycosidic Bond - Carbs
- Peptide bond - Protein
Hydrolysis Reaction
Hydrolysis reaction = Forms Monomers from Polymers
Chemical bond is broken using water
Water molecule is used
...
e
...
•
Disaccharides - Formed by condensation of 2 monosaccharides
•
Maltose - Formed by 2 α-glucose molecules
•
Sucrose - Formed by Glucose and Fructose molecule
•
Lactose - Formed by glucose and galactose molecules
Carbohydrates
Reactions
Glycosidic bond formed
2x
Monosaccharides:
Glucose
Galactose
Fructose
Condensation Reaction
H2O Lost
Glycosidic bond Broken
Hydrolysis Reaction
H2O Used / Gained
Beta Glucose
Alpha Glucose
Disaccharides:
Sucrose
Lactose
Maltose
Carbohydrates
•
Polysaccharides - Formed by the condensation reaction of many
Glucose molecules
•
Glycogen - Formed from α-glucose
•
Starch - Formed from α-glucose
•
•
Including Amylose and Amylopectin
Cellulose - Formed from β-glucose
All Polysaccharides are joined by Glycosidic bonds
Carbohydrates
Starch
Starch
- Carbohydrate in plant cells
- Energy storage of excess glucose
from photosynthesis
...
- β-glucose molecules form straight cellulose
chains
...
Benedicts Test
Test for Reducing and NonReducing Sugars
Reducing Sugars
1
...
3
...
Add 2cm3 of reducing sugar solution
...
Leave for 10mins in a Hot water bath
...
Positive - Reducing
Sugar Present
Green - Yellow - Orange Brick Red Precipitate
formed
-
-
Negative - Non reducing
sugar present
Sample stays Blue
Higher Conc
...
2
...
4
...
6
...
Add excess dilute HCl acid
Leave for 10mins in a Hot water bath
...
Add Benedict’s solution
Colour change shows if non-reducing sugar is
present
Positive - Non -reducing
Sugar Present
Negative - No Non
Reducing sugar or
reducing present
...
Biuret Test
•
Make test solution alkaline by adding NaOH (Sodium
Hydroxide)
•
Add Copper (II) sulphate
Positive Result - Solution goes purple
Negative Result - Solution stays blue
Lipids
•
Different from Carbohydrates & Proteins - Not from
from long monomer chains
•
Made from varied of components
•
•
All made up from Hydrocarbons
Triglycerides and Phospholipids both types of lipid
All Lipids have the same basic structure but the
hydrocarbon tail varies
...
Double layer formed from heads
attracted to water in cytoplasms inside
and outside of cell
...
•
Dipeptides - 2 amino acids joined by a peptide bond
...
Proteins are 1+ polypeptide chains
-
All living things share the same 22 Amino acids
Difference is what makes the carbon-based
variable side chain
Proteins
Structure
•
Primary structure - The amino acid sequence in a polypeptide chain
•
Secondary Structure - Hydrogen bonds form between amino acids in the chain
...
•
Tertiary Structure - More hydrogen + ionic bonds form between the chain - causes more coiling / folding of
the chain
...
•
•
For single chain proteins (only 1 peptide chain) the Tertiary structure is the final 3D structure
...
•
Quaternary structure is the way polypeptide chains are arranged together
...
Peptide bonds are formed
Chemical bond linking amino acids
Proteins
Shape & Function
Proteins shape determines it’s function
-
Enzymes - Spherical shape from folded polypeptide chains
Soluble in solution
Role in metabolism - Breaks down food
Synthesise large molecules
-
-
Antibodies - 2 short and 2 long polypeptide chains
Polypeptide chains are bonded together
Variable regions in amino acids - very variable antibodies
Transport Proteins - Channel proteins
Made of hydrophobic and Hydrophilic amino acids
Cause folded ‘channel’ structure of protein
Transport molecules and ions through membrane
-
Structural Proteins - Physically strong - Long, parallel polypeptide
chains
Cross-links provide extra strength
Keratin - Hair and Nails
Collagen - connective tissue - 3 polypeptide chains
-
Chains coiled together - provides structural support in animal
Proteins as Enzymes
Enzymes are biological catalysts which lower the
activation energy of a reaction
•
Enzymes catalyse metabolic reactions for functions within cells and the
body in general
...
Substarte has to has Correct complimentary shape to
fit active site
Has to be specific substrate to
make changes to the active site
Proteins as Enzymes
Enzyme Inhibitors
Competitive inhibitors
-
-
Compete with substrate for enzymes active site
Similar shape to specific substrates
Able to bind to the active site
No reaction occurs
Prevents the substrate from binding to the active
site
...
of inhibitors +
substrates
High Inhibitor conc
...
- More likely to form
enzyme-substrate complex - rate or reaction not
affected so much
...
Enzyme inhibition - relative conc
...
- fewer substrates able to
bind to active site - reduce rate of reaction
High Substrate conc
...
-
Specific complementary shape which fits only own
substrate
Shape specific due to tertiary structure
When substrate binds to active site the Enzyme Substrate complex is formed
How enzymes lower activation
energy
1
...
2
...
Due to kinetic energy increasing the chance
of enzyme substrate collision
If temperature exceeds optimism point then
bonds begin to break and Active site denatures
...
- =increase rate of reaction
- More enzyme molecules = more chance of enzyme
colliding with substrate
...
-
Higher substrate conc
...
4 Specific Nitrogen based bases
Adenine - A
Only one specific pairing option
Thymine - T
Adenine - Thymine
Cytosine - C
Cytosine - Guanine
Guanine - G
-
All nucleotides have same SugarPhosphate backbone
Joined by phosphodiester bond
Formed in condemnation reaction
Sugar-Phosphate backbone provides structure and protection
for Hydrophobic bases
DNA and RNA
Complementary base pairing
•
Polynucleotide chains are joined by Hydrogen bonds between
nitrogenous bases
...
•
A = T - 2 Hydrogen bonds
•
C ≡ G - 3 Hydrogen bonds
•
Complimentary base pairing - ensures equal amounts of bases in DNA
molecules
...
DNA Helicase (enzyme) breaks hydrogen bonds between polynucleotide chains
- DNA unzips itself - separate strands formed
2
...
- Complementary base pairing - free floating nucleotides are attracted to exposed
complementary bases
...
3
...
ATP
General
•
•
Adenosine Triphosphate
The molecules used to provide energy in all living
processes
•
DNA replication
•
Active transport
•
Cell division
•
Protein synthesis
-
•
Made of glucose molecules - Glucose molecules
cannot directly provide energy to organisms - has
to be made into ATP
...
Structure of Water - H2O
- Covalently bonded
- Polar molecule - Electronegativity of
Hydrogen and Oxygen atoms
•
•
Hydrogen bonds - formed between water
molecules
- Due to charge difference between atoms
- H∂+ + O∂-
Water
Properties
Metabolite
-
Involved in metabolic reactions including
condensation
...
Ions are surrounded by oppositely charged
water molecules
Totally surrounded ‘Dissolved’
Allows useful substances can be dissolved in
water
Transported around body
...
2
Cells
Key definitions
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Prokaryotic - Single celled organisms
Eukaryotic - Complex multi-cellular organisms
Tissue - A group of cells all working in the same way
Organ - A collective of tissue working together
Cellulose - Carbohydrate found in Plant cell walls - increases rigidity
Chitin - Carbohydrate found in Fungal cell walls - replaces cellulose
Glycoprotein - A carbohydrate attached to a Protein
Attachment Proteins - Protein on Virus surface - allows attachment to Host cell
receptor proteins
TEM - Transmission electron microscopes - internal structure of cell
SEM - Scanning electron microscopes - shape and surface of cells
Artefacts - Accidental objects in microscope sample - common in E
...
Cell fractionation - Way of separating organelles from cells - Homogenisation,
Filtration, Ultra-centrifugation
Cells
Key definitions
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Interphase - Growth and protein synthesis stage of cell cycle
Mitosis - Cell division stage of cell cycle
Daughter cell - Genetically identical cell to parent cell
Chromatids - Condensed chromosomes - strand of X-structure
Centromere - Region of chromosomes which are attached to spindle fibres
Binary Fission - The replication of prokaryotic cells
Viral replication - The replication of viruses using host cells
...
e Antibiotic resistance
...
Net movement - The overall movement of molecules
Facilitated Diffusion - The diffusion of substances through transport proteins in cell-surface
membrane
Channel proteins - Transport protein found in the cell-surface membrane which allows the
diffusion of charged molecules
Carrier proteins - Transport proteins found in cell surface membrane that facilitates the
diffusion of large molecules
Osmosis - The diffusion of water moving down a water potential gradient from a high water
potential to a low water potential
...
Cells
Key definitions
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•
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•
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Antigens - Molecules fond on plasma membrane which generate an immune
response when detected
...
- Maintains the pressure inside
Contains Sap - Water, Sugar, cells
- Keeps cell rigid - outward
Salt
Membrane bound organelle pressure
- Prevents wilting
Image
Organelles
Organelle Name
Description
Golgi Apparatus
+ Vesicles
Fluid filled sacs
Close to Nucleus
Vesicles - Surround
Apparatus
Small membrane bound circles
Function
-
-
To engulf and digest foreign
cells or dying organelles
Carries Digestive enzymes
Lysozyme’s - digestive
enzyme
-
Synthesise Proteins
-
Support cells structure
Prevent cell changing shape
Allow movement of substances
in and out
-
Lysosome
Round membrane bound
organelle
No clear internal structure
Type of golgi vesicles
Ribosome
Non-membrane bound
Free-floating
Cytoplasm or attached to RER
...
C
Cell-surface membrane
Made of lipids and proteins
Controls the movement of substances in and out of cell
Cell Wall
Supports cell structure - Muerin - Glycoprotein
Flagella
Tail like structure - Moves cell - Not on all Prokaryotes
Free-floating Circular DNA
Replaces Nucleus - 1 Long DNA molecule - NOT attached to Histone proteins
Free floating in the Cytoplasm
Plasmids
Loops of unattached DNA - contain feature like Antibiotic resistance
Passed on by Prokaryotes via connecting tissues + Binary fission
Caspule
Slime layer - surrounds cell - provides protection from immune system attacks
Viruses
General
-
-
-
Acellular - Non living
Nucleic acids surrounded by proteins
Smaller than prokaryotic cells
Reproduce by invading and
injecting genetic material into cells
Cells become viral host - replicate
viral DNA
No Plasma membrane
No cytoplasm
No Ribosome
No self replication
Nucleic Acid
Protein coat -Capsid
Attachment proteins
Attachment proteins allow viruses to attach to host cells
Studying Cells
Microscopes
Magnification - How many times bigger and image is compared to its actual size
Resolution - How detailed the image is - How well 2 points can be distinguished
Image = Actual x Magnification
Actual = Image ÷ Magnification
Image
Actual Size
Magnification = Image ÷ Actual
Magnification
Studying Cells
Microscopes
Electron Microscopes
Optical Microscopes
-
-
Uses light to form an image
Max resolution = 0
...
0002µm
Higher resolution than Optical
See all organelles
Higher magnification = x1,500,000
Produces B&W image
Scanning Electron
Microscopes (SEM’s)
Electromagnetic beam transmitted — sample
Removes electrons from sample
Collected in cathode ray tube - forms image
Shows shape and surface of cell
Can be used on thick samples
Has to be used in vacuum
Cannot be performed on live specimens
Lower resolution
Studying Cells
Cell fractionation - Way of separating organelles from
rest of cell
1
...
Solution must be kept :
Ice-Cold - to reduce lysosome activity breaking down other cells
Isotonic - maintains constant water potential - preventing cells swelling from osmosis
Buffer - Maintain pH - prevent Organelle damage
2
...
Ultra-centrifugation - Organelles are separated by being spun @ increasing speeds
Heaviest organelles separated first - Pellet
Other organelles in supernatant
Continue spinning @ higher speed to separate smaller organelles
Order of Separation
Nucleus, Chloroplast, Mitochondria, Lysosomes, Endoplasmic reticulum, Ribosomes
Cell Replication
Cell Cycle
Not all cells are able to divide
Eukaryotic cells which can reproduce - follow cell cycle
Starts with cell formed - Ends with cell 2 daughter cells
Interphase: Cell growth + DNA replication
ATP concentration rises - energy for division
-
-
Growth1 - Cell growth, Organelle + Protein
production
Synthesis1 - DNA replicated
Growth2 - Cell grows + more proteins made
Mitosis: - Cell division
Parent cell divides to produce 2 genetically identical
daughter cells
Needed for the growth of multicellular organisms - growth
+ repair
Cell Replication
Mitosis
1
...
Metaphase
Chromosomes align on cell equator
Pulled into position by spindle fibres
3
...
Telophase
Chromatids condense and uncoil - return into chromosomes - spindle fibres spread
Nuclear envelope forms around both nuclei
5
...
Cell Replication
Binary Fission
1
...
Growth
Cell physically grows + DNA & Plasmids move to poles of cells
3
...
Division
Cytoplasm completley divides
2 daughter cells are produced
Identical DNA, variable plasmids
...
Virus attaches to host cells receptor proteins
Attaches to host cell surface - complementary receptor proteins
Virus evolved to exploit cell surface receptor proteins
Different viruses have different attachment proteins
Require different receptor proteins
Able to effect multiple cells
2
...
Genetic proteins and material replicated by host cells ‘machinery’
4
...
Cell Replication
Cancer
•
•
•
•
Mitosis = Controlled cell division
Controlled by genes
Cancer = Uncontrolled cell division
Cancer - tumour which invades surround tissue
•
Tumours formed by continuous cell division
...
C
are all the same
Acts as a barrier between cytoplasm and
inner organelle
Partially Permeable
-
-
-
-
-
-
Cell Membranes
Structure
-
Membrane structure
Lipids - Phospholipids
Proteins
Carbohydrates - attached to phospholipids or Proteins
GlycoProteins
GlycoLipids
Fluid Mosaic model
Phospholipids form a continuous double layer
Phospholipid bilayer
‘Fluid’ - Phospholipids are constantly moving and not fixed
Proteins scattered through bilayer
Channel Proteins
Carrier Proteins
Receptor proteins - detect chemical signals for cell to coordinate
response to
...
to a low conc
...
-
Non-polar substances can diffuse freely through
bilayer - Soluble in hydrophobic centre layer
...
gradient
Molecules are able to move both ways
Cell Membranes
Factors effecting diffusion
•
-
Concentration Gradient - Higher the concentration gradient = Faster diffusion
...
E - Microvilli - adapted for dissuasion - Thin, large surface area
Cell Membranes
Facilitated Diffusion
Facilitated Diffusion - Used for the diffusion of Large
molecules ad charged ions
Without FacDif, simple Dif of large substances would be
slow and inefficient
-
Large molecules diffuse into cells via channel &
carrier proteins in the cell membrane
-
Passive Process - does not require energy for it to
take place
Particles are moved down concentration gradient
Cell Membranes
Carrier & Channel Proteins
Carrier Proteins
-
Move large molecules through the membrane
Glucose, Amino acids
-
A large molecule attach to carrier proteins
active site
Protein shape shape to suit molecule
Molecule is released other side of membrane
-
Channel Proteins
-
Transports charged ions across bilayer
Na+, K+ etc
...
gradient is increased
Cell Membranes
OSMOSIS
Osmosis - The diffusion of water across a
partially permeable membrane from region pf
high water potential to a region of low water
potential
...
Isotonic - When two solutions have the same
water potential
No net movement occurs
-
-
Hypotonic solutions - Higher water potential
than cells - water moves into cell - cells swell
Hypertonic - Lower water potential than
cells - water moves out of cells - cells shrink
Cell Membranes
Factors effecting Osmosis
•
Water potential (ψ) Gradient - Higher water
potential = faster osmosis
As Osmosis occurs, WP(ψ) become equal - levelling
off Rate of Osmosis
•
Thickness of Surface - Thinner surface = shorter
distance = faster Osmosis
•
Surface Area - Larger SA = Faster Osmosis
...
Requires energy from ATP hydrolysis - Active Process
Similar to FacDif - Uses carrier proteins
...
to high concs
...
protein it is transported
across membrane
Cannot be re-transported - carrier protein is no longer
complementary
Cell Membranes
Factors affecting Active Transport
•
Speed of carrier proteins - Faster proteins work = Faster
Active Transport
•
N˚ of carrier proteins - More proteins = faster active
transport
•
Rate of respiration in cell - ATP needed for A
...
- ATP
produced via respiration - slower respiration = slower A
...
•
pH around membrane - pH affects tertiary structure of
carrier proteins - active site denatures - carrier proteins less
able to transport molecules = Slower A
...
Cell Membranes
Co-Transport
•
Uses Co-Transporter proteins - type of carrier proteins
2 Molecules bind to protein active site
•
Conc
...
gradient
•
I
...
co-transport of Glucose into cells with Na+
Cell Membranes
Co-Transport (Absorption) of Glucose
1
...
gradient of Na+ ions - High conc
...
low conc
...
2
...
gradient
Diffuses down conc
...
of glucose in cell than in blood
3
...
gradient through channel proteins
...
Phagocyte recognises foreign antigens on pathogen
...
Cytoplasm of phagocyte moves around pathogen (engulfs) the
pathogen
3
...
Lysosome fuses with phagocytic vacuole - releases lysosomes which
digest pathogen
...
Phagocytes present antigens on surface to activate immune
response - Killer + Helper T Cells
Cells and the Immune System
T - Cells
- Type of W
...
C which produces chemical response or Lymphokines
Helper (CD4) T-cells
-
Release cytokines (chemical signals), which
Stimulates Killer (CD8) T - cells
Stimulates B-Cells
Activate phagocytes
Stimulate phagocytosis
Cytotoxic CD8 T-cells
-
Kill abnormal & foreign cells
Combine w
...
B
...
greater than B-cell N˚
...
All vaccines are tested on animals before being tested humans
Animal based substances used to produce a vaccine
2
...
3
...
4
...
Attachment proteins attaches to receptor proteins on cell membrane
of Helper CD4 T-cells
...
The capsid is released into the cell - uncoats within the cell, releasing
HIV RNA into the host cell cytoplasm
...
Reverse transcriptase is used to make a complimentary strand of DNA
from the Viral RNA template - complementary base pairing
4
...
Host cell replicates the viral RNA and enzymes are used to make viral
proteins from the Viral DNA code
...
The produced proteins and RNA are assembled into new viruses which
leave the host cell to infect other CD4 cells
...
HIV
Symptoms of AIDS
•
Initial Symptoms Minor infections of mucus membranes
Respiratory infections
•
Late AIDS - Very low T
...
e
...
Application area contains antibodies
complementary to hCG protein - Attached to a
coloured bead
2
...
Urine moves up test strip carrying coloured bead
with it
4
...
- Coloured beads are trapped in test strip
Monoclonal antibodies
Elisa Test
-
ELISA - Enzyme linked immunosorbent assay
Tests if patient have any antibodies for specific antigens
Used for medical diagnosis’
Antibody is used with enzyme attached
Enzyme reacts with a substrate to produce a colour change
Direct Elisa
-
-
Indirect Elisa
Uses 2 different antibodies
Specific antibodies to antigen being tested
for
unspecific enzyme carrying antibody
attaches to specific antibody causing a
reaction when solution is added
...
3 Exchange &
transport systems
Exchange systems
Key Terms
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•
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•
•
Surface area: Volume ratio - affects how quickly substances i
...
Multi-cellular organisms - organisms which have large diffusion pathways, require
exchange and transport systems to efficiently move substances
...
Spiracles - Pores on insects surface allowing gas in & out - attached to tracheas
Trachea (Insects) - The chitin air pipes transporting gas for gas exchange in insects
Tracheoles - Smaller thin tubes (1 cell thick) carrying gas to & from cells in insects
Gill filaments - Thin plates making up a gill - increases surface area
Lamella - Structures covering gill filaments increasing surface area
Counter-current system - Ensures efficient O2 diffusion form water to blood - Short
Exchange systems
Key Terms
•
•
•
Amylase - Breaks polysaccharides into disaccharides
Membrane-bound disaccharidases - Enzymes attached to ileum in small intestine
Circulatory system - transports blood supplying useful and removing waste substances
from around the body
Exchange systems
Key Terms
•
•
•
•
Tissue Fluid - Fluid which surrounds cells in tissues
Hydrostatic pressure - The pressure exerted on the capillary wall
Lymph system - System which collects excess tissue fluid and transports it back
to arteries
Phloem - Transports dissolved assimilates around the plant
Surface area : Volume Ratio
Affects how quickly substances are
exchanged in an organism
...
Heat Exchange
Metabolic activity inside cells creates heat which need
to be transported away
...
Large volume = smaller surface area Harder to loose heat
...
Means smaller organisms need a high
metabolism to maintain a constant
temperature
...
- Minimising heat loss
...
- Increasing heat loss
-
-
Whether an animal is compact or
not depends on the temperature
of its environment
...
Exchange Organs
Organs which supply cells with substances they
need and remove waste products
...
Some cells are deep within body - too big distance
...
Multi-Cellular organisms need Specialised EXCHANGE ORGANs
Need efficient system to carry substances - Mass Transport systems
...
Plants need O2 for Respiration - CO2 waste gas
...
- Adapted to their function - Large Surface
area
...
- Gas moves in through Stomata’s in the
epidermis
...
- Guard Cells control the opening and closing
- Increases rate of diffusion
...
-
Stomata’s make a shorter diffusion
distance - increases rate of diffusion
distance
Xerophytes
Plants which have specially adapted to live in warm, dry or windy
environments - where water loss is a problem
...
gradient between Water & Air
- Prevents water evaporating from the leaf
-
Leaf hairs - Surround the epidermis to trap water
vapour around the stomata
...
-
Waxy Cuticles - Increase diffusion distance - reduces
evaporation
...
- Air moves into Tracheae through pores on surface Spiracles
-
O2 moves down trachea into tracheoles into cells
(tracheoles - smaller - like capillaries)
- O2 Concentration gradient high to low - increases
diffusion into cells
...
-
O2 & CO2 moves in and out of insects via abdominal
movements
Concentration gradient of O2 - High (Spiracles) Low (Tracheoles)
Water controls gas exchange - can be lost through
spiracles
...
-
Water enters mouth and passes out through Gills
...
- Gill Filaments - increase surface area for gas
exchange
...
- Lamellae increase surface area furthermore
-
Lamellae is covered in capillaries and has a thin cell
surface layer
- This increases the rate of diffusion by:
- Reduces the diffusion distance
- Increase the surface area - more possible places
for diffusion to occur
...
- Means steep concentration
gradient is maintained by water
and blood
...
Intercostal Muscles
-
-
-
Air enters the Trachea when you breathe in
...
Bronchi branch into smaller bronchioles
...
- Gas exchange occurs in the alveoli’s
...
Relatively low O2 conc
...
near high O2 conc
...
-
One cell thick - short diffusion pathway
...
-
Elastin helps alveolus to recoil and maintain
its shape
...
-
Large surface area increase rate of diffusion
- More blood in contact with alveolar
epithelium
-
Concentration gradient with CO2 and O2
Ventilation
Inspiration and Expiration controlled by Intercostal muscles, ribcage
and diaphragm
Inspiration
Expiration
-
-
External intercostal and diaphragm contracting
Ribcage moves upwards and outwards
Diaphragm flattens
Increase in the thoracic cavities volume
Cavity volume increases - reduces pressure in
lungs below atmospheric pressure
...
Normal Expiration is a passive process - doesn’t
require energy
...
e
...
•
Emulsified lipids hydrolysed into micelles
•
Micelles are fatty acids + glycerol attached to bile salts
•
Micelles allow digested, hydrolysed lipids to be absorbed
Digestion
Digestion of Proteins
•
Proteins peptide bonds are hydrolysed by endo/exopeptidases
•
Endopeptidases - Hydrolyses internal peptide bonds - form
protein fragments
•
Increases the surface area for Exopeptidases to work on
Exopeptidases - Hydrolyses external peptide bonds to form
protein fragments and an amino acid
...
Monoglycerides and
fatty acids are lipid
soluble across the
phospholipid bilayer
Diffusion across cell
membrane
Absorption of
Amino acids
-
Na+ ions pumped into
ileum of sINT (Active
transport)
-
Diffuses down
concentration gradient
into cells with amino
acids through Na+
dependent
transporters
...
Partial Pressure of Oxygen (pO2)
pO2 is the measure of Oxygen
concentration
Greater Concentration of dissolve O2 in
cells - the higher the pO2
-
As pO2 increases = Haemoglobin’s
affinity for oxygen increases too
Oxygen loads onto O2 where
the pO2 is high - Alveoli’s
Oxygen unloads where the pO2
is lower - Respiring cells
Dissociation curves
When the gradient is high and When gradient is low / levelling off
O2 saturation is low, the partial the O2 saturation is high - Partial
pressure is low - meaning
pressure is High - No oxygen is
oxygen is offloaded for
offloaded - Haemoglobin is fully
respiring cells
loaded
...
Bohr Effect + pCO2
-
-
-
pCO2 is the partial pressure of CO2 (CO2 concentration)
Affects the unloading of oxygen
Haemoglobin unloads oxygen more readily at higher pCO2
...
Respiring cells produce more CO2 which increases to the rate of
Oxygen unloading
...
Ventricles relax, Atria contracts
- Atria contract - Decreases atric volume
- Increase pressure
- Blood forced though atrioventricular valves into ventricles
- Ventricular volume + pressure increase due to blood
2
...
Ventricles and Atria relax
- Higher pressure in arteries than ventricles
- Semi-lunar valves shut - preventing backflow
- Blood returns to heart - Atria fill due to pressure in Vena Cava and
Pulmonary Vein
- Ventricles relax - Atric pressure forces AV valves open
- Blood flows passively into ventricles
Blood Vessels
Arteries
-
-
-
Carry blood from the heart
to body
Thick, elastic walls stretch & recoil with heart
beat and pressure increase
Small lumen Maintains + withstands
high pressure
Inner endothelium
folded - allows artery to
stretch
Arterioles
Veins
-
-
-
Formed after arteries carries blood to
capillaries
Directs blood around the
body
Muscles restrict or
allow blood flow
-
-
Carries blood back to heart
under low pressures
Wide, less elastic lumen
Increases volume of
blood carried
Contains valves prevent back flow
Blood flow increases by
contracting muscles around
vein
Blood Vessels
Capillaries
-
-
-
Branched off Arterioles
Smallest blood vessel
1 Cell thick wall - short
diffusion pathway
1 RBD thick lumen
Efficient gas
exchange and
diffusion
Always near exchange
tissues
Network of capillaries forms capillary bed
Tissue fluid
Fluid which surround cells in tissues
Made of small molecules pushed out of blood plasma
Oxygen, water + nutrients
NO RBC or proteins - too big to pass through capillary
Cells absorb O2 from tissue fluid - relate metabolic waste into it
1
...
Pressure in Tissue fluid
= Outward pressure force
2
...
Pressure forces substances out of blood plasma
Causes hydrostatic to drop at end of capillaries
3
...
- substances move out into tissue
fluid
Water re-enters blood plasma via osmosis
4
...
Transpiration of water from leaves (Evaporation)
2
...
Cohesion of water pulls more water into Xylem - Whole column of water is pulled
upwards
Plant transport
Transpiration
Factors effecting transpiration
1
...
Temperature - ↑ Temp = ↑ Transpiration - Warmer water molecules =
more energy
evaporate quicker
Increases water potential gradient between environment and cell =
faster diffusion of water
3
...
Wind - ↑ Wind = ↑ Transpiration - Lots of air movement blows water
molecules away from stomata - increase water potential gradient - More water
moves out
Plant transport
Potometer
-
Potometer - Estimates the rate of transpiration
Assumes water uptake replaces the water lost in transpiration
Things to remember
-
Cut stem underwater - prevent air from entering the xylem
Seal all joints - make the potometer is airtight
Assemble underwater - No air can enter the potometer
Plant transport
Phloem
Transports dissolved substances around the plant
Sieve like elements are living cells which form the
transporting tube - No nucleus
Each sieve cell has a companion cell for each sieve tube
element
Conducts the living functions fro sieve cells
-
-
-
Phloem allows translocation to happen
The movement of assimilates from source cells to sink
cells
-
Enzymes maintain the concentration gradient from
source to sink cells
Catalyse reactions to change assimilates
Ensures concentration gradient
Plant transport
Mass Flow Hypothesis
Translocation - The active process movement of assimilates to where they are needed
...
Source Cells - Mesophyll / palisade cells in leaf produce
assimilates
2
...
Assimilates - Lower the water potential of Phloem solution causes the osmosis of water from Xylem - creates a high
Hydrostat
...
4
...
raises water potential - Water
moves out of phloem into the xylem
Plant transport
Evidence of mass Flow Hypothesis
Evidence supporting
-
-
-
Bark removal - fluid budge forms above ring
Higher concentration of assimilates more water
Assimilates cannot move past ring phloem in bark - translocation unable to
take place
Phloem pressure + aphids - aphids drink
from the phloem
Leave mouthpart in phloem
Sap flows out of phloem
Greater flow higher up stem
Higher pressure
Radioactive tracers
Metabolism inhibitors
Evidence Against
-
Sugar travels to many sinks
Not just the sink with the higher pressure
gradient
-
Sieve plates create barrier
Very high pressure required for solution
the pass through at a reasonable rate
Genetic information,
variation and relationships
between organisms
3
...
1 - Genes
Key Terms
•
•
•
•
•
•
•
•
•
•
•
•
Histones - The protein which DNA coils into chromosomes around - found in
Eukaryotic cells, providing support for DNA
...
4
...
4
...
Acids in all living organisms
Mutations - Change in base sequence of chromosomes
Base deletion - When a base is physically removed from a cell
Base substitution - When a new base replaces an original base
Mutagenic Agents - Substances which increase the chance of a mutation occurring
Chromosome non-disjunction - The failure of a chromosome to separate fully
Diploid cells - Cells with a full set of chromosomes
Haploid cells - Cells with half the number of chromosomes
Chromatids Homologous Pair Gamete - Sex cells
3
...
3 - Genetic Variation,
mutations + Meiosis
Key Terms
•
•
Haploid
Diploid
3
...
4 - Genetic Diversity
Key Terms
•
•
•
•
•
•
•
•
•
Genetic diversity - The N˚ of different alleles of genes in a species or population
Gene Flow - The introduction of new alleles to a population from another
population - maintains genetic diversity
Alleles Frequency - Relative frequency of an allele in a specific population
Natural Selection - Survival of the fittest
Reproductive Success - The passing of genes to offspring in such a way that
they too can pass on the genes
Selection Pressure - Change in the environment occurs - reducing population as
some individuals cannot survive
Evolution - The gradual change in a species overtime leading of greater diversity
Directional Selection - Individuals with alleles of an extreme type are more likely
to survive
Stabilising Selection - Individuals with alleles and characteristic towards the
middle of the allele range are more likely to survive
3
...
4 - Genetic Diversity
Key Terms
•
•
•
•
Behavioural Adaptations - How organisms act to increase survival chance
Physiological Adaptations - Process’s inside and organisms body which
increases it’s chance of survival
Anatomical Adaptations - Physical and structure features of an organisms body
which increases chance of survival
Inhibition Zone - The gap between antibiotics and bacteria
3
...
5 -Species & Taxonomy
Key Terms
•
•
•
•
•
•
•
Species - Organisms belonging to the same species are able to produce fertile
offspring
Courtship behaviour - Behaviour which attracts potential mates for
reproduction - can be used to classify species
Phylogentic Classification - The classification of organisms based on their
evolutionary origin and relationships
Taxon - A group of the phylogentic classification heiracrhy
Taxonomy - The science of classification
Binomial System - A way of naming all organisms - universally recognised
Genome Sequencing - Way of comparing DNA to find how closely animals are
related
DNA, Genes & Chromosomes
General
Eukaryotic - DNA wound around Histones (proteins) coiled repeatedly - condenses into chromosomes in
nucleus
Histones - Allow DNA to coil into chromosomes
NB - Mitochondria and Chloroplasts have individual DNA similar to prokaryotic DNA
Prokaryotic - DNA forms circular chromosomes
Coiled and condensers to fit into cells
Circular + short = no proteins needed
...
s of Amino acids
Base orders determine amino acids coded for
Each Amino acid coded by a ‘triplet’ (Codon) of bases
DNA copied onto mRNA - 1st stage of protein synthesis
-
Functional RNA - RNA other than mRNA
Performs special tasks during protein synthesis
Coded form by DNA which doesn't code for Amino acid polypeptide chains
DNA, Genes & Chromosomes
Coding and Non-coding regions
Exons - Coding regions of a gene
Introns - Non-coding regions of a gene
Eukaryotic DNA - Contains multiple non-coding repeats between genes
Repeats over and over but doesn’t code for polypeptides
-
Genes occupy fixed positions on DNA molecules
Fixed position called a locus
Alleles - different arrangements of the same gene
Code for different versions of the same polypeptide chains
-
3 DNA bases form a coding triplet
Each triplet codes for a specific Amino Acid
- The genetic code if universal, non-overlapping and degenerate
...
RNA Polymerase attaches to beginning of DNA/genes
Hydrogen bonds are broken between strands of the DNA
Strands become separate
DNA uncoils - exposing bases - Both strands become genetic templates
2
...
3
...
RNA polymerase reaches stop signal in DNA
RNA polymerase stops making mRNA + detaches from DNA strand
mRNA leaves nucleus form nuclear pores
Travels into cytoplasm heading for ribosomes
DNA + Protein synthesis
Editing mRNA
Eukaryotic Cells
Prokaryotic Cells
-
-
Pre-mRNA contains introns and exons
Splicing of pre-mRNA removes introns
mRNA is formed
-
Splicing takes place within the nucleus
mRNA is produced directly from DNA
No splicing
Prokaryotic DNA contains no introns
DNA + Protein synthesis
Translation
Occurs in ribosomes in the cytoplasm of all cells
Amino acids are joined together by peptide bonds to form polypeptide chains
1
...
1
...
tRNA anticodon complementary to mRNA codon
tRNA with a complementary anticodon moves into the Ribosome
tRNA attaches itself to mRNA codon - complementary base paring
2nd tRNA molecule attaches to next codon in the same way
-
Amino acids carried by tRNA undergo condensation reaction - dipeptide chain
produced
DNA + Protein synthesis
Translation
3
...
Acids once their tRNA it complementary to the codons and in correct
order
3
...
Process continues until stop codon is reached
Polypeptide moves out of ribosome
Protein is produced
Translation is complete
4
...
Acids in all living organisms
- Evidence of a common ancestor + evolution
Genetic diversity, mutations + Meiosis
Mutations
Genetic mutations - Change in base sequence of chromosomes
Arrises spontaneously in DNA replication
Base deletion - When a base is physically removed from a genetic code
Base substitution - When a new base is swapped with the original base in a
genetic code
Base Deletion
Base Substitution
-
-
Always alters the genetic code
Causes shift in genetic code
-
Smaller problem than Base deletion
Genetic code is degernate
Chance that mutation codes for the
same protein
Amino Acid sequence is not always
changed
Mutagenic agents - Increase the chance of a spontaneous mutation occurring
UV radiation
Ionising radiation
Chemicals + Viruses
Genetic diversity, mutations + Meiosis
Chromosome mutations
Chromosome mutations - can arise spontaneously by chromosome
non-disjunction during meiosis
-
Inherited condition - Errors in gametes - hereditary cells
-
Failure of chromosomes to separate fully
- Results in Down’s syndrome
Genetic diversity, mutations + Meiosis
Meiosis
Diploid cells - Body cells - Full set of chromosomes
Diploid number of chromosomes
Chromosome from each parent
Humans have 23 chromosome pairs - 46 Chromosomes
Diploid N˚ = 2(23) = 46
2n - Homologous chromosome pairs
Cell Division which takes place in reproductive organs
Diploid - Haploid
Only in Eukaryotic organisms
Genetic diversity, mutations + Meiosis
Meiosis
1
...
DNA condenses to form double armed chromosomes
Made from 2 sister chromatids
Chromatid produced by DNA replication - Joined at centromere
3
...
Homologous pairs separate - halving chromosome number
5
...
4 Haploid cells produced are genetically different
Daughter cells = Genetically different - Independent segregation
of homologous chromosomes
Genetic diversity, mutations + Meiosis
Mitosis vs Meiosis
Mitosis
-
Genetically identical offspring
2 Daughter cells
Uses replicated chromosomes
-
No crossing over or independent
segregation
No genetic variation
Meiosis
-
Genetically different offspring
4 Daughter cells
Chromosomes not replicated
Chromosomes have different
arrangements and sets of genes
-
Genetic variation - crossing over and
independent segregation
- Produces 4 Haploid cells
-
Produces 2 Diploid cells
Genetic diversity, mutations + Meiosis
Genetic Variation
Crossing over of chromosome
-
-
Meiosis I — Homologous chromosomes
come together and pair up
Chromatids twist around each other
Bits of chromatids swap over
• Same genes - Homologous pairs genes in the same position
Different combination of alleles
Results in haploid daughter cells all having
different chromatids - Increased
genetic variation
Independent segregation
of chromosomes
-
-
-
Homologous pairs are made up of
chromosomes from maternal and
paternal sides
Separation of chromosomes in Meiosis I
is completely random
Random what chromosomes end up in
daughter cells
Daughter cells have different
combinations of chromosomes
‘Shuffling’ of chromosomes increases
genetic variation
Genetic diversity, mutations + Meiosis
Gametes & Sexual Reproduction
Gametes - Sex cells
Haploid (n) number of chromosomes (Half)
Copy of 1 chromosomes from each homologous pair
-
Gametes join together to form diploid cell
Zygote
Fertilisation - Haploid + Haploid = Diploid - 1/2 Maternal + 1/2 Paternal
Any sperm can fertilise any egg
Random cell - Zygote produced have different combinations of
chromosomes from haploid cells
-
Fertilisation increases Genetic diversity as Genetic material is mixed
Genetic diversity & Adaptations
Genetic Diversity
Genetic Diversity - The n˚ of different alleles of genes in a species or
population
I
...
- Large Allele variation = High Genetic diversity
- Low Genetic Diversity = Population unable to adapt to change - leads to migration
or extinction
-
Genetic diversity increased by:
Mutations in DNA - forming new alleles
- Can be advantageous or problematic i
...
causes cancer or gives antibiotic
resistance
Different alleles introduced into population from new individuals joining and
reproducing wth group
- Gene flow
Genetic diversity & Adaptations
Founder Effect and Genetic Bottlenecks
Founder Effect
-
-
-
Occurs when a group of a population are
separated
Form a new population with fewer alleles
Allele Frequency in new population very
different to original pop
...
Different reproductive success in populations
Individuals with beneficial allele are more likely to survive + reproduce
Allele passed on
2
...
Allele Frequency of beneficial allele increases over generations
Leads to evolution of the species
Beneficial Allele becomes more common in species
Genetic diversity & Adaptations
Types of Selection
Directional Selection
- Individuals with alleles and characteristics
of an extreme type are more likely to
survive
Caused in response to a change in the
environment and new selection pressures
Stabilising Selection
- Individuals with mid-range
characteristics are more likely to survive
and reproduce
Occurs when there is no change in the
environment - reduces characteristics range
Genetic diversity & Adaptations
Types of Selection
-
Directional Selection
Stabilising Selection
Antibiotic resistance
Human Birth weights
Antibiotics administered - Selection
pressure on Pop
Title: Full As Level Biology Notes
Description: Full As Level Biology notes for AQA
Description: Full As Level Biology notes for AQA