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Nucleus, contains DNA + controls what the cell does
Cytoplasm, gel-like substance, chemical reactions happen
Cell Membrane, holds cell together, controls what goes in + out
Mitochondria, where most reactions for respiration happen
Cell Wall, cellulose, supports cell
Large vacuole, contains cell sap – weak mix of sugar + salt
Chloroplasts, photosynthesis occurs hear, contains chlorophyll

Bacterial cells
- Chromosomal DNA, long circular chromosome, controls cells activities + replication, floats free in cytoplasm
- Plasmids, small loops extra DNA, contains genes like drug resistance
- Flagellum, hair like structure rotates to make bacterium move
- Cell wall, supports cell
Specialised cell, cell that performs a specific function
Microscopes, studies cells
- Light microscopes, invented in 1590s, sees small things
- Electron microscopes, invented in 1930s, see really small things
Magnification = Length of image
Length of specimen
DNA, double helix of paired bases
- Bases, chemicals that hold DNA strands together
- Adenine (A)
- Cytosine (C)
- Guanine (G)
- Thymine (T)
- Weak hydrogen bonds, hold base pairs together
- Gene, section of DNA
- Sequence of bases code for specific protein
Rosalind Franklin + Maurice Walker discovered DNA has a helical structure – directing beams of x-rays onto crystallised DNA
James Watson + Francis Crick adapted the ideas to make a model of DNA with the bases
Protein synthesis
- Proteins = stringing amino acids in an order together
- 20 different amino acids = thousands of different proteins
- Codon, set of three bases, codes for specific amino acid
- DNA determines genes switched on or off
- Proteins help to make other things e
...
cell membranes
Proteins, made in cell by organelles called ribosomes
1
...
DNA strand unzips – hydrogen bonds break
b
...
Complimentary base pairings
2
...
Translation
a
...
Ribosome sticks amino acids together, makes polypeptide
Mutations, a change in an organism’s DNA base sequence, effects change in shape and function of protein
- Harmful, can cause genetic disorder e
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cystic fibrosis
- Beneficial, could produce new characteristics that is beneficial to an organism
- Neutral, some neither nor beneficial e
...
don’t affect protein’s function

Enzymes, biological catalysts, proteins, work inside or outside
of cells, specific to substrate
- Reduce the need for high temps
- DNA replication – enzymes copy cell’s DNA before
mitosis/meiosis
- Protein synthesis – hold amino acids in place + form
bonds between them
- Digestion – enzymes secreted into gut to digest
different food molecules
Catalyst, a substance which increases the speed of a reaction,
without being changed or used up
Chemical reactions, involve things being split apart or joined
together
Substrate, molecule changed in the reaction
Measuring the rate of enzyme reactions
- Change in temperature changes
reaction rate
- Changes in pH changes reaction rate
- Higher the substrate concentration,
the faster the reaction

Human genome project
Positive
- Predict + Prevent diseases
- Develop new + better medicines
- Accurate diagnosis
- Improve forensic science

Negative
- Increased stress
- Gene-ism
- Discrimination by employers + insures

Genetic engineering uses enzymes to cut and paste
genes
- Useful gene cut from organism’s chromosomes
using enzymes
- Enzymes used to cut another organisms
chromosome and then insert the useful gene
- Technique produces genetically modified (GM)
organisms
Can benefit humans
- Reducing vitamin A deficiency
- Golden rice contains 2 genes, enable the
rice to produce beta carotene
- Producing human insulin
- Can be produced quickly + easily
- Treats diabetes
- Increasing crop yield
- Modified genes makes crop resistant to stuff
Controversial topic
- Long term effects have not been able to be monitored as it’s a new phenomena
- Possible reduce in farmland biodiversity
- Not everyone is convinced GM crops are safe
- Transplanted genes may be passed on to weeds – superweeds

Mitosis
- DNA spreads out in long strings
- DNA forms x shaped chromosomes – each ‘arm’ is an exact duplicate to the other
- Chromosomes line up at the centre of the cell, cell fibres pull them apart
- Arms of each chromosome go opposite ways
- Membranes form around each set of chromosomes, become nuclei of two new cells
Two new cells genetically identical to each other + to parent cell
Meiosis
- Duplicates DNA
- FIRST DIVISION, chromosome pairs line up
at the centre of the cell
- The pairs then pulled apart, each new cell
has one copy of each chromosome, some fathers
some mothers (random amount of each
- SECOND DIVISION, chromosomes line up at
the centre of the cell, cell fibres pull them apart
(like mitosis)
4 gametes with only a single set of chromosomes
produced

Cloning mammals

Cloning, type of asexual reproduction
- Electric shock stimulates mitosis of cell
Uses
- Help with shortage of organs for
transplants, pigs bred with suitable organs for
humans
- Study of animal clones = understanding
of embryo, aging + age related disorders
- Used to preserve endangered species

Issues
- Reduced gene pool, fewer different alleles in population
- A closely related population catches a disease = all wiped out
- Cloned mammals = short life span
- Risks + problems associated with cloning
- Often fails
- Clones born with genetic defects
- Clones’ immune systems often unhealthy = suffering form more diseases
Embryonic stem cells, differentiate into any cells
- Most animals cells = loss to differentiate cells quickly
- Plant cells never lose the ability
- Stem cells found in bone marrow, aren’t as versatile as embryonic stem cells
Stem cells may be able to cure diseases = huge scientific interest
- Adult stem cells already used, bone marrow transplant cures sickle cell anaemia
- Experiments done on early embryonic stem cells, grow them, make them specialise into certain cells
- Might possible to differentiate stem cells to create specialised cells that replace damaged ones
- Ethical concerns
- Human embryos should not be used for scientific experiments, should find other sources of stem cells
- Embryos used normally unwanted ones – if not used for science would be destroyed
- Some countries banned stem cell research, UK under strict guidelines but can do it

Respiration, the process of breaking down glucose to release energy, which goes into every cell
- How all living things get energy from food
Aerobic respiration, uses oxygen
- Most efficient way to release energy from glucose
Glucose + Oxygen  Carbon Dioxide + Water (+energy)
Anaerobic respiration, doesn’t use oxygen
- Releases less energy
- Build-up of lactic acid, can give you cramp
- Advantage – can keep using muscles
- After anaerobic respiration = oxygen debt
- Amount of oxygen required = Excess post-exercise oxygen consumption (EPOC)
- Must keep breathing hard after to exercise to replace oxygen loss
- Heart rate stays high to get oxygen round body quicker
- Oxygen converts Lactic acid  CO2 + Water
Glucose  Lactic Acid (+ energy)
Cardiac Output = Heart Rate x Stroke Volume
Diffusion, the gradual movement of particles from an area of high concentration to an area of low concentration
Circulatory system, carries glucose, oxygen + CO2 around body in blood
Glucose comes from breaking down food in digestive system
Oxygen comes from air breathed into lungs, CO2 breathed out
Capillaries, supply all cells with glucose + oxygen, + take away CO2
Substances move from cell to capillary by diffusion
- Cells respire and use up oxygen + glucose = low concentration in cells
- Concentration in blood is higher so oxygen + glucose diffuse from capillaries into cells
- Cells respire + produce lots of CO2 = high concentration in cell
- Concentration in blood is low so CO2 diffuses into from cell into capillary
Photosynthesis, process that produces glucose (food) in plants
Carbon Dioxide + Water  (Sunlight, Chlorophyll)  Glucose + Oxygen
Leaves adapted for efficient photosynthesis
- Broad, large surface area exposed to light
- Contain lots of chlorophyll in chloroplasts to absorb light
- Stomata, holes in leaves, open + close to let CO2 + O2 in and out,
- Stomata, allow water vapour to escape – transpiration
Rate of photosynthesis
- Rate increases with light intensity
- Not enough CO2 slows down
- Temperature, too low = enzymes work slower, too high = enzymes denature
Osmosis, the movement of water
molecules across a partially permeable
membrane from a region of high water
concentration to a region of low water
concentration
- Water molecules pass both
ways as water moves randomly
- More water on one side than
the other = steady net flow
Root hair cells take in water by osmosis
- Usually a higher concentration of water in the soil than there is in roots
Root hairs also absorb minerals – absorbed by active transport
- Uses energy from respiration to help plant pulls minerals into the roots
XYLEM – tubes transport water + minerals from the root to the rest of the plant
PHLOEM – tubes transport sugars from the leaves to growing and storage tissues
Transpiration – caused by evaporation + diffusion of water from inside the leaves
- Creates shortage of water in the leaf, more water drawn up from roots, constant
transpiration stream of water through the plant
- Supplies plant with constant supply of water for photosynthesis

Distribution of organisms
- Pooters
- Pitfall traps
- Sweep nets
- Pond nets
- Quadrat
- Transect
Evidence of evolution
- Fossil, any trace of an animal or plant that lived long ago
- Fossils found in rock layers tell us 3 things
- What the creature/plant looked like
- How long ago they existed
- How they’ve evolved
- Fossil record is incomplete
- Few dead plants turned into fossils
- Soft tissue decays completely
- Fossils yet to be discovered
Pentadactyl limb, limb with 5 digits
- Seen in many species
- Each species = similar bone structure
- Human + bat both Pentadactyl limbs but not same
function
- Similarities in bone structure = evidence all evolved from
common ancestor
Growth, increase in size or mass
- Size – height, length, width or circumference
Wet mass, mass including all the water in the body
- Dry mass, mass of organism discounting water
Growth involves
- Cell differentiation, process by which cells change to become specialised
- Cell division, mitosis
- Cell elongation, plant cell expands = makes plant bigger
Growth in animals = cell division (mainly for growth + repair) + eventually stop
Growth in plants = grow continuously, cell division @ tips + roots, cell elongation = everywhere else
Tissues, group of similar cells working together to carry out a particular function
Organs, group of different tissues working together to perform a particular function
Organ systems, group of organs working together to perform a particular function

Heart = part of circulatory system
Right atrium receives deoxygenated blood (from body) through
vena cava
Deoxygenated blood moves to right ventricle
Blood pumped up to lungs via pulmonary artery
Left atrium receives oxygenated blood (from lungs) through
pulmonary vein
Oxygenated blood moves to left ventricle
Blood pumped around body via aorta
Left ventricle = thicker wall than right, needs more muscle bc pups
blood round whole body not just to lungs
Valves prevent backflow of blood

Blood + blood vessels = part of circulatory system
Red blood cells
- Carry oxygen from lungs around body
- Biconcave disk = large surface area to absorb oxygen
- Contains haemoglobin, which contains iron
- Combines with oxygen = oxyhaemoglobin
- No nucleus = more room for haemoglobin
- Lack of iron = anaemia = can’t carry enough oxygen
- More red blood cells = more oxygen getting to cells
- People living in high altitudes = more blood cells bc less oxygen in air so compensate with more cells
White blood cells
- Change shape to suit consuming unwelcome microorganisms
- Produce antibodies = to fight microorganisms
- Produce antitoxins = neutralise toxins produced by microorganisms
- Low white blood cell count = increased risk of infection
- High count = infection or leukaemia (blood cancer)

Platelets
- Small fragments of cells
- Help blood to clot
- Stop flow of blood
- Stop microorganism entering
- Lack of platelets = excessive bleeding + bruising

Plasma
- Pale yellow liquid = keeps blood fluid
- Transports everything;
- Red, white blood cells + platelets
- Nutrients e
...
glucose + amino acids
- Carbon dioxide
- Urea
- Hormones
- Antibodies + antitoxins

Arteries
- Carry blood away from heart
- Under high pressure = strong + elastic walls
- Walls thick compared to lumen + contain thick layers of muscle
- No valve
- Elastic fibres
Capillaries
- Arteries branch into capillaries
- Very small
- Carry blood really close to every cell in body = exchange substances with them
- Permeable walls = substances easily diffuse in + out
- Supply food + oxygen, take away CO2
- Walls only 1 cell thick = increases rate of diffusion bc less distance over which it occurs
Veins
- Capillaries joins up to form veins
- Carry blood at low pressure = no thick walls
- Bigger lumen than arteries = help blood flow despite low pressure
- Valves to keep blood flowing in right direction

Digestive system
Digestive enzymes breakdown insoluble molecules (starch, proteins + fats) into soluble ones (sugars, amino acids + fatty acids)
- Carbohydrases (e
...
amylase) digest starch to sugars
- Proteases (e
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pepsin) breakdown proteins to amino acids
- Lipase digests fat to fatty acids + glycerol
Digestive enzymes produced in different places
Mouth
Oesophagus
- Food moistened by saliva from salivary glands
- Tube takes bolus from mouth to stomach
- Amylase enzyme from salivary gland in saliva –
- Lined with muscles that contact to move food
breaks down starch
along, by peristalsis
- Food chewed to form bolus (ball of food) them
swallowed
Stomach
Liver
- Pummels food with muscular walls
- Bile produced
- Produces pepsin
- Neutralises stomach acid
- Produces HCl
- Emulsifies fats
- Kill bacteria
- Pepsin works best at pH 2 – acidic levels
Gall Bladder
Pancreas
- Bile is stored
- Produces protease, amylase + lipase enzymes
- Releases bile into small intestine
- Release them into small intestine
Small intestine
Large intestine
- Produces protease, amylase + lipase enzymes
- Excess water absorbed from food
- Where ‘food’ absorbed out of digestive system
into body
Visking tubing, model for the gut
- Only lets small molecules through + not big molecules, like gut
- Cheaper + easier than using an animals gut
- Speed of digestion + absorption will be different due to different size
Add 5cm3 of starch solution + 1cm3 of amylase
solution to visking tube
Rinse outside of tube under tap
Put visking tube into beaker of distilled water
Test for starch using iodine and glucose using
Benedict’s reagent in the water after 10 mins
Benedict’s reagent starts blue + turns red
dependant on amount of glucose present
Iodine stays orange if no starch present
No starch will be present bc starch molecules too big to pass through visking tube
Benedict’s reagent turns red bc glucose present bc amylase broken down starch into sugars that can pass through
The higher the concentration of amylase the greater the change in colour of Benedict’s reagent from blue to red (could be inbetween)
- Higher concentration of amylase = more active sites to break down starch = starch broken down at faster rate

Gut = alimentary canal
Muscle tissue all around digestive system
- Squeezes food along
- Squeezing action = peristalsis
- Waves of circular muscle contractions push food along gut
- Waves of longitudinal muscle contractions run slightly ahead
to move food along

Bile
-

Produced in liver
Stored in gall bladder
Released into small intestine
Bile = alkaline so neutralises stomach acid if to acidic
Enzymes in small intestine work best in alkaline conditions – bile neutralises he acid
Emulsifies fats – breaks fat in tiny droplets = lipase works quicker bc larger surface area to target

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Inside small intestine
Three features that make absorbing digested food into bloodstream
efficient;
- Big surface area = digested food absorbed quicker into blood
- Single layer of cells = digested food diffuses quickly
- Good blood supply via capillary network = quick absorption into
blood stream

Villi

Functional foods, food with health benefits beyond being nutritional
Probiotics, live bacteria
- Bifidobacteria + Lactobacillus
- Bacteria similar to ones naturally found in gut
- Added to foods e
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yogurt, soya milk, dietary supplements
- May help to keep digestive system healthy, by replacing gut bacteria lost in antibiotic treatments
Probiotics, food supply for ‘good’ bacteria in digestive system
- Indigestible carbohydrates
- Occur naturally in food e
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leeks, onions, oats
- Some people take supplement of them bc not enough obtained in normal diet
- Thought they promote growth of good bacteria = improve health of immune system + strengthens immune system
Plant stanol esters
- Lower blood cholesterol + reduce risk of heart disease
- Occurs naturally in plants but in small amounts
- Produced commercially by using bacteria to convert sterols into stanols
- Food manufacturers use them e
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spreads, dairy products
Not all health claims scientifically proven
- Is the report a scientific study, published in a reputable journal?
- Was it written by a qualified person (not connected with people selling it)?
- Was the sample of people asked/tested large enough to be reliable?
- Have there been other studies which found similar results?



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