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Biology GCSE
Note- In all the symbol equations the numbers should be smaller than the letters
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Divide rapidly by splitting into (binary fission)
No nucleus
No mitochondria
Contains plasmids (loop of DNA)
No cellulose in cell walls
Diffusion - the movement of particles from a high concentration gradient to a low concentration
gradient
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The greater the
concentration difference the steeper the concentration gradient, factors that can affect diffusion
are higher temperature, shorter distance of diffusion and steeper gradient
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Osmosis - the specific type of diffusion which is the movement of water molecules from a high
concentration gradient to a low concentration gradient
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The
movement is from a dilute solution to a concentrated solution
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Concentrated solution means the cell becomes flaccid and soft
Plasmolysed cell means the cytoplasm had pulled away from the cell wall
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Active transport - uptake of molecules against a concentration gradient
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It has a low concentration outside the cell and a high
concentration inside the cell
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Root hair cells absorb mineral ions from very dilute solutions in the soil into the cell
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Specialised cells carry out a particular function
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Tissues are made up of a group of similar cells which work together to carry out a particular
function
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Organ systems are made up of a group of organs that work together to carry out a certain
function
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Epithelial tissue - covers some parts of the body like inside the gut
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Epithelial tissue - covers the inside and outside of the stomach
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Carbohydrates- carbon hydrogen oxygen
Made up of 2 sugars - glucose sucrose
Glucose is C6H12O6 sucrose - C12H22O11

Complex carbohydrates - long chain of sugar units joined together (condensation reaction)
Starch- used to store sugar molecules in plants
Glycogen- used to store sugar in animals
Cellulose- very strong fibres used to make plant cell walls
Lipids - carbon hydrogen and oxygen

Fats and oils
Provides huge amounts of energy (respiration)
Makes cell membranes and hormones
Provides insulation
Made of glycerol and 3 fatty acids

Protein - carbon hydrogen oxygen nitrogen
Long chain of amino acids - control proteins function
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g collagen
Makes hormones e
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Only ONE substrate molecule will fit in the active site
All joined together - enzyme substrate complex / bind together temporarily/reaction will take
place rapidly
Products are released and a new substrate molecule binds to the enzymes active site - lock and
key hypothesis
Factors that affect the rate that enzymes work at:
- PH
- Temp
- Substrate concentration
As temperature increases the faster the enzymes and the substrate molecules move, and the
kinetic energy increases
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More enzyme -substrate complexes are formed
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Above the optimum temp, means the molecules move around and vibrate so much that the
enzyme changes shape
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The enzyme is
destroyed/denatured
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PH affects the forces that hold together the amino acid chains which have a specific shape
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The incorrect shape means they do not
bind and the enzyme is denatured
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Carbohydrase - convert starch - sugar Syrup (glucose)
Isomerase - convert sugar syrup - fructose
Starch - not sweet/ insoluble
|
Carbohydrase
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Sugar syrup - sweet / used in cakes sweets biscuits etc
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Enzymes are secreted (pass out of the cell) and break down /digest food molecules
Large insoluble ----------- Small soluble

Fat ------ glycerol + fatty acids
Lipase

Protein -------- amino acids
Protease

Starch ------ sugar /glucose
Amylase

Minerals/vitamins/ water are small enough to be absorbed by the body without being broken
down, so they are not digested
Fibre cannot be broken down why is why it cannot be absorbed by the body
Fibre ----- faeces

Function of small intestine:
Produces all 3 types of enzymes
Food is completely digested
-- insoluble to soluble
Soluble products are absorbed into the bloodstream (mainly diffusion)

Mouth - saliva is made and it contains amylase
Gallbladder - where bile is stored
Liver- produces bile
Stomach - produces protease which works best with acid so to help protease work , hydrochloric
acid is made here
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Adaptions to increasing the rate of food absorption:

Villi + microvilli has a large surface area for diffusion
Thin (1 cell thick) short distance for diffusion
Good blood supply to carry absorbed food away= maintains concentration gradient
Very long

Bile
Produced in liver
Stored in gall bladder
Neutralises stomach acid (bile is an alkali)
Provides the optimum PH for the enzyme that works in the small intestine
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Lipase
Fats ------ fatty acids + glycerol
Digestion

Breathing - ventilation
The respiratory system supplies oxygen to all parts of the body
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Breathing out/ exhaling - volume of lungs/thorax decrease then the diaphragm relaxes, the air is
pushed out and the ribs are lowered
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Exchanging gasesAs you breathe you take in oxygen that you need for respiration and get rid of waste carbon
dioxide
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Adaptations for efficient gas exchange:
-Very large surface area for diffusion
-good blood supply + good O2 supply = maintains a large concentration gradient
- thin permeable walls = short diffusion pathway
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Negative pressure ventilator - (iron lung) when air is pumped back into the iron lung, the
pressure inside increases causing air to move out of the lungs
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Disadvantages are the tube in the trachea is uncomfortable making it more difficult to eat and
talk
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Aerobic respiration
- complete break down of glucose --- releases large amounts of energy
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- chemical reaction that occurs in mitochondria
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g birds/mammals maintain optimum conditions for
enzymes to work in
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g aa+aa+aa = protein (prefer in synthesis e
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Anaerobic respiration - why is it not efficient over a long period of time?
- only a small amount of energy can be released
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Why might they start to respire anaerobically?
Not enough oxygen reaches the muscles during exercise, so they use anaerobic to obtain energy
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g bacteria used to form yoghurt
FERMENTATION
increase in heart rate --- more O2 and glucose --- more aerobic respiration and CO2

Effects on exercise
Heart rate increases
Breathing rate/depth of breathing increases
Glycogen stored in muscles -- glucose

HomeostasisThis is the maintenance of a constant internal environment
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Automatic control systems in the body keep conditions relatively constant
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- skin - heat is lost by radiation
-vasodilation increases heat loss by the blood vessels widening and allowing more warm blood
close to the surface
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- flat hairs stand upright so trapped air is heated by body
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Vasoconstriction - blood vessels narrow so less blood flows near the surface
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Controlling blood sugarMonitored and controlled by the pancreas in the co-ordination centre
Pancreas contains special receptor cells that are sensitive to blood glucose conc
Insulin - allows cells to increase uptake of glucose ( blood --- cells) e
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E absorbed food
Both hormones are secreted by the pancreas

Insulin
Glucose -----------------glycogen
|_______Glucagon______|

Glycogen stores are full, glucose is converted to and stored as lipids

Type 1 diabetes-pancreas does not produce enough insulin
-controlled by:
Diet (avoid too much sugar)
Exercise
Injecting insulin (after monitor blood sugar)

Type 2 diabetesBody cells do not respond to insulin properly
Controlled by:
Diet
Exercise
Drugs that help cells respond to insulin

Having diabetes means you are enable to break down glucose info energy
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Inhaling insulin - benefits
Don't have to inject
Pain free

Problems Potentially leads to lung cancer
expensive
Don't know how much to take
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Competition - two factors animals may have to compete for are:
Food
Space/territory
Trees compete for:
Minerals (nutrients)
Light
Water
This is in order for the trees to grow
Organisms living in different habitats need different adaptations
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g migration
Huddling

Functional -

Related to metabolic and reproduction (inside the body)
Low metabolism -need less food
-reduce water loss

ExtremophilesAn organism that can survive and reproduce in the most difficult conditions
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Other bacteria have adaptations so they can
grow and reproduce in low temperatures
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Thick fur on the top of the body for shade and thin fur elsewhere to allow easy heat loss
Large surface area to volume ratio to maximise heat loss
Slit-like nostrils and two rows of eyelashes to help keep sand out
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A habitats - means a place where plants and animals live
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g part of the playing field)
An organism might be more common in one area than another due to differences in
environmental factors between the two areas
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2 methods: -give quantitive data about the distribution
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Study how the distribution changes across an area
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Work out population size:
Work out mean number of organisms per m squared
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Mean = total number of organisms
by the total number of quadrats
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Mark out a line
Collect data along the line
Count organisms that you're interested in that touch the line
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Oxygen is released as a by-product

Glucose is converted into starch for storage
Glucose -------- starch
(Soluble) (Insoluble)

Limiting factors Light intensity
Temp/CO2

How plants use glucoseRespiration Releases Energy = build larger molecules from smaller ones e
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Plants grow towards sources of water and light
which they need to survive and grow
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Plant hormones are used in weed killers, rooting powder and to control fruit ripening
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Negative tropisms - plants grow away from the stimulus
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Root Negative photo tropisms grow
in the direction of the force of
gravity
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Root Positive geo tropisms grow in
the direction of the force of
gravity
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Shoots and roots respond differently to high concentrations of auxin
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If tips are covered, light cannot reach them
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Auxins have the opposite effect on root cells, the shaded side contains more auxin but the shaded
side grows less than the light side causing the root to bend away from the light
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Plant hormones control the rate of plant growth:
Weed killers - attack some plants but not others
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Controlled fruit ripening - make sure plants don't go ripe before the shops
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Biomass - mass of living material
Energy - chemical energy made of an organism = biomass + water
Food chains:
Represent the transfer of biomass/energy between organisms
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The mass of a living material is called the biomass

Photosynthesis
Solar ------------- chemical energy
Radiation CO2 Stored in BIOMASS
(100kJ) (1KJ)

More biomass = more cells = more protein/carbs/fats etc
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Each stage in a food chain is called a tropic level

Pyramids of biomass - each stage is less than the one before because:
- some of the material is not digested and absorbed by the faeces/urine/wastes
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- not all of the organisms are eaten = may die
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Energy losses:
Eaten 100
Digested/absorbed 80
Biomass:
Units for growth - 10
Heat - 60
Urine - 10
Not digested/ faeces 20
The biomass/ energy not lost is converted into new cells/tissue = growth

Available for the next stage in the food chain
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G

Grass -------------- Cow

Energy is lost from animals in three main ways:
Waste materials - faeces = indigestible parts of food e
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Urine - products of metabolism e
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Glucose + oxygen ---- carbon dioxide + water + energy

Keeping a constant body temp - maintaining a constant body temp above the environmental temp
requires a lot of energy
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96/4 x 100 = 24%
Herbivore - large loss of energy in undigested food = faeces (cellulose is difficult to digest)
Carnivore - little loss of energy in undigested food (meat/protein is easier to digest
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g insects
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E
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Absorbed
Waste/dead plants ------------ decomposers
and animals

Decomposers = bacteria/fungi
They digest/break down the organic material using using enzymes that they secrete
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g nitrates
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Low temperature stops/slows down digestion -- slows growth
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Oxygen conc
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E no O2 = no energy for growth
Living organisms remove materials from the environment when they grow
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Natural recycling of materials

Defending ourselves against diseases
Pathogen - micro-organisms that cause infectious disease
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Virus-has a protein coat and is made of genetic material (strand of DNA)
-reproduce inside living cells (makes them hard to treat because virus' have no cytoplasm etc
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Droplet infection- Cough/sneeze/talk/ breath in droplets containing pathogens
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Direct contact- spread by direct contact of skin
Examples - sexually transmitted diseases
Contaminated food and drink - raw/undercooked/contaminated food or drinking water containing
sewage
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Producing special proteins called antibodies that kill microbes (many ribosomes and
mitochondria)
Produce special chemicals called anti-toxins that neutralise toxins released by microbes
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Immunity- white blood cells make a specific type of antibodies that kill a specific pathogen
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Antibodies are produced rapidly by the MEMORY
cells and destroy the pathogen before it can multiply and make us ill= IMMUNE
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Pain killers/aspirin
Anti-bodies - cure bacterial diseases by killing pathogenic bacteria
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g penicillin damages bacteria cell was (does not harm animal cells)
Specific bacteria should be treated by specific antibiotics
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Changing pathogens - to a new strain
The new strain may be resistant to:
-Antibiotics
-Vaccinations

The new strain will spread rapidly because:
-no effective treatment
-people are not immune
Antigen changes shape (different protein)
No memory cells
Slower immune response- cannot make the correct antibody quick enough
Pathogen multiplies
Releases toxins
ill

Resistance to antibiotics:
Overuse --- used to treat non-serious infections
Inappropriate use-- farm animals to increase growth
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Antigens- unique proteins on the surface of pathogens
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Vaccinations - active artificial immunity

In a form that stimulates the immune response without giving the person the disease
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Many will remain in blood stream
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MMR vaccine
Stimulates specific WBC's to make specific antibodies
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Why is area around the well clear? - bleach has killed the bacteria
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End of experiment - Petri dish is put into a steriliser to kill any bacteria left
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- maximum temp in schools (25) to reduce likelihood of growing harmful MO's to humans
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Body stops virus from entering
- having a scab to stop blood clots
-having dead skin layers

Carbon cycle -

Photosynthesis/respiration/decay
1
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CO2 is returned to the atmosphere by respiration

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