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Biology – likely long answer questions
Compare prokaryotic cells and eukaryotic (4)
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70s vs 80s ribosomes
Prokaryotic smaller
Cell wall in some of both
Prokaryotes have pili, flagella
Nucleolus vs nucleoid
Naked DNA vs DNA associated with protein
No mitochondria vs mitochondria
Plasma membrane in both
Slime capsule in prokaryotes
Cytoplasm in both
Golgi, RER, etc in eukaryote only

Draw the phospholipid bilayer (4)

Outline the role of membrane proteins (4)
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Channel protein – allows passive movement of large substances
Pump protein – active transport of certain substances across membrane
Junctions – connect two cells
Enzymes – localises metabolic pathways
Recognition – markers for cellular identification
Anchorage – attachment points for cytoskeleton and extracellular matrix
Transduction – receptors for peptide hormones

Compare membrane models (8)
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Davson-Danielli – two layers of protein flank central phospholipid bilayer
Lipo-protein sandwich
Dark segments – protein layers (wrong)
Issues: assumed uniform thickness and lipid-protein ratio
Assumed internal and external symmetry
Did not account for permeability of certain substances
Temperatures at which membranes solidified did not correlate with proposed
model
Membrane proteins discovered to be insoluble – hydrophobic and varied in size
Fluorescent antibody tagging – mobile and not fixed in place
Freeze fracturing – rough surfaces – transmembrane proteins – not only on outside
Singer-nicolson (fluid-mosaic) – proteins embedded within bilayer

Discuss types of membrane transport (4)
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Membranes are semi-permeable and selective
Passive processes:
o Simple diffusion – small or lipophilic molecules
o Osmosis – movement of water molecules from low to high potential
o Facilitated diffusion – large or charged molecules
Active processes:
o Primary active transport – direct use of metabolic energy to move materials
against concentration gradient
o Secondary active transport – coupling molecules
o Vesicular transport – rER synthesises proteins, sER synthesises lipids and
carbs
o Bud and vesicle forms – to golgi, cis to trans, modification – exocytosis
o Endocytosis

Explain the endosymbiotic theory (4)
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Eukaryotes come from prokaryotes
Prokaryotes engulfed by phagocytosis
Remained undigested – contributed function
Lost function over time
Evidence:
o Double membranes
o Susceptible to antibiotics
o Fission division
o DNA – naked and circular
o Size of ribosomes 70S

Describe the process of mitosis, drawing a diagram (8)
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Cell cycle: interphase – G1, S, G2, M phase
Interphase processes:
o DNA replication
o Organelle duplication
o Cell growth
o Transcription/translation
o Obtaining nutrients
o Cellular respiration
Roles of mitosis:
o Tissue repair
o Growth
o Asexual reproduction
o Development of embryo
Prophase – supercoiling and condensing, nuclear membrane dissolves,
centrosomes move to poles and spindles form
Metaphase – spindles attach to centromeres, contract, middle, line
Anaphase – contraction, sister chromatids separate, poles, separate chromosomes
Telophase – decondense, membrane reforms, cytokinesis begins
Cytokinesis – division of cells into two genetically identical cells

Explain how water is the medium of life, comparing to methane (8)
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Hydrogen bonding – polar associations
Cohesive and adhesive – high surface tension – capillary action
Solvent properties:
o Ionic/polar (hydrophilic) substances dissolve
o Important medium for metabolism and transport
Thermal properties:
o Can absorb large amounts of heat energy before changing state – hydrogen
bonds
o Very high specific heat capacity
o Very effective coolant (evaporation of sweat requires heat from body)
Other properties:
o Transparent – for photosynthesis and vision
o Expands when frozen – less dense – floats on water
Vs methane:
o Polar vs non-polar
o Higher heat capacity
o Higher boiling point

Compare types of lipids and their health risks (8)
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Saturated fatty acids – no double bonds – solid at room temperature
Unsaturated – double bonds – liquid at room temperature
Cis / trans:
o Cis – H atoms on same side, kink in chain, loosely packed and liquid, occur
in nature, good for health
o Trans – H atoms on different sides, no kink, tightly packed and solid,
processed food, bad for health
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Draw an amino acid

Discuss levels of protein structure (4)
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Primary: order of amino acid sequence; covalent peptide bonds
Secondary: fold into repeat patterns, alpha helices and beta pleated sheets,
hydrogen bonds between amine and carboxyl groups
Tertiary: 3D arrangement of polypeptide; interactions between side chains
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g
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g
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g
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gs haemophilia, Red-green colour blindness

Give arguments for and against GMOs
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Benefits of GM crops:
o Improve nutrition
o Grow in wide range of environments
o Reduce costs and deforestation
o Reduce spoilage
Risks:
o Unexpected health issues
o Patent protections could restrict access
o Possible cross pollination with weeds
o Could compete with native plants, reducing biodiversity
Example:
o Bt corn is a transgenic crop – produces insecticide
o Bt corn may be impacting survival of monarch butterflies
o In lab conditions, butterfly mortality is higher when fed plants dusted with
Bt pollen – there is insufficient field evidence to support this

Explain natural and artificial cloning
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Clone – groups of genetically identical organisms – derived from single original
parent cell
Various methods of cloning exist for animals and plants – humans can also clone
organisms or tissues artificially
Animal cloning
o Binary fission – divides equally into two clones, flatworms
o Budding – cells split off from parent – smaller clones – occurs in hydra and
yeast
o Fragmentation – new organisms grow from separated fragment of parent
o Common to starfish and some species of annelid worm
o Parthenogenesis – embryos formed from an unfertilised ovum – in some
fish, insects, reptiles, amphibians
o MZ twins – fertilised eggs split in two – identical embryos
Plant cloning
o Vegetative propagation – small tissues of plant induced to grow
independently
o Totipotent meristematic tissue capable of differentiation – use stem
cuttings
Artificial cloning – embryo
o Separating embryonic cells into groups; pluripotent – each cell can form
cloned offspring – occurs after random fertilisation – cannot control
genetics

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Adult
o Somatic cell nuclear transfer – nucleus removed from adult body cell and
fused with enucleated egg cell – electric shock stimulates division –
growing embryo implanted into surrogate

Discuss nutrient cycling in an ecosystem
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Finite supply
Autotrophs convert inorganic nutrients into organic molecules
Heterotrophs ingest organic molecules and may release inorganic by-products
Saprotrophs breakdown nutrients in dead organisms and return them to the soil

Explain how a Chi Squared test is used
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Applied to quadrat sampling to determine if there is a statistically significant
association between the distribution of two species
Presence/absence recorded
Identify expected frequencies
Null – no association
Alternative – association
Expected frequencies = row total x column total / grand total
Chi-squared formula = X2 = sum of (O-E)2 / E
Degree of freedom = number of rows – 1 x number of columns -1
Determining significance
P<0
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e
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g
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18J – specific heat
capacity of water
Equation = energy = mass x 4
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5 – assist in digestion of food, activate proteases, prevents
infection
o Stomach lined with mucus – protects from acid
o Bicarbonate from pancreas neutralises stomach pH
Certain foods may also neutralise stomach acids, impairing digestion and
increasing chances of infection
Proton pumps in parietal cells of gastric pits
o Proton pumps secrete H+ ions via AT which combine with Cl- ions to form
HCl
Certain medications and disease conditions can increase secretion of H+ ions,
lowering pH
o PPIs irreversibly bind to proton pumps – prevent H+ secretion
o Raises pH preventing acid reflux
o People taking PPIs may be prone to gastric infections

Cause of anorexia
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Individuals severely limit amount of food they intake
Most common in females with body image anxiety
Body begins to break down heart muscle – heart disease
o Blood flow reduced and BP may drop
o Heart may develop dangerous arrhythmias and become physically
diminished

Explain intestinal villi adaptations
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Microvilli – ruffling of epithelial membrane increases SA
Rich blood supply – dense capillary network rapidly transports absorbed products
Single layer epithelium – minimises diffusion distance between lumen and blood
Lacteals – absorbs lipids from intestine into lymphatic system
Intestinal glands – exocrine glands release digestive juices
Membrane proteins – facilitates transport of digested materials into epithelial cells

Discuss digestive infections
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Stomach ulcers – inflamed and damaged areas in stomach wall – exposure to
gastric acids
Correlation between Helicobacter pylori and development of stomach ulcers
o Can survive acid conditions by penetrating mucus lining
o Anchors to epithelial lining
o Inflammatory immune response damages epithelial cells of stomach –
including mucus-secreting goblet cells
o Degradation of protective mucus lining – exposes stomach wall to gastric
acids – causes ulcers
Prolonged presence of stomach ulcers may lead to development of stomach cancer
over many years
o Can be treated by antibiotics
Cholera - Infects intestines – causes acute diarrhoea and dehydration
o Releases a toxin that binds to ganglioside receptors on surface of intestinal
epithelium cells
o This toxin is internalised by endocytosis and triggers production of cyclic
AMP within cell
o Cyclic AMP activates specific ion channels within membrane – efflux of
ions from cell
o Build up of ions in intestinal lumen draws water from cells and tissues via
osmosis – diarrhoea
o As water is being removed from body tissues, dehydration will result if left
untreated

Explain the role of the liver in processing nutrients
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Carbohydrates
o Excess glucose taken up and stored as glycogen in liver
o When blood glucose levels drop, liver breaks glycogen down into glucose
and exports it to body tissues
o When hepatic glycogen reserves become exhausted, liver synthesises
glucose from other sources
o These metabolic processes are coordinated by pancreatic hormones, insulin
and glucagon
Proteins
o Body cannot store AAs – must be broken down
o AA breakdown releases NH2 and is potentially toxic
o Liver removes this (deamination) and converts to harmless product
o Amine group converted into urea by liver – excreted within urine by
kidneys
o Liver can also synthesise non-essential amino acids from surplus stock
Fats
o Excess carbs and proteins to fatty acids and triglycerides
o Synthesis of phospholipids and cholesterol
o Compounds then stored by liver or exported to cells by different types of
lipoproteins
o LDS – cholesterol to cells for cell membrane and steroid synthesis
o HDLs cholesterol from cells to liver
o LDLs are bad, HDLs good
o Surplus cholesterol is converted by liver into bile salts – can be eliminated
from body via bowels
Liver acts on drugs and toxins in blood – often soluble making excretion difficult
o Compounds are converted into less harmful and more soluble forms – then
excreted from the body
Two pathways:
o 1) toxins converted into less harmful chemicals by oxidation, reduction and
hydrolysis reactions; mediated by cytochrome p450 – produce damaging
free radicals neutralised by antioxidants in liver
o 2) converted chemical attached to another substance – conjugation
o Renders compounds even less harmful and functions to make it water
soluble
o Water soluble compounds can now be excreted from the body within urine
by the kidneys

Outline different types of plasma proteins
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Produced by liver
Produced by rough ER in hepatocytes – exported into blood via Golgi
Number of different types:
o Albumins – osmotic pressure
o Globulins – immunity and transport
o Fibrinogens – clotting
o Low levels of other proteins

Discuss the breakdown of erythrocytes by the liver
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Erythrocytes have few organelles and no nucleus
Short lifespan – must be constantly replaced
Kupffer cells engulf erythrocytes and break them down
o Break down haem into globin and heme groups
o Globin digested by peptidases to form amino acids (recycled/metabolised)
o Heme groups – iron and bilirubin
o The iron is complexed with protein to avoid oxidation
o Iron can be stored within liver in ferritin
o Can also be transported to the bone marrow within transferrin

Explain jaundice
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Excess of bile pigment, bilirubin
o Produced naturally
o Normally, liver conjugates bilirubin to other chemicals and secretes in bile
o Excess – leaks into surrounding tissue fluids
May be caused by
o Liver disease (impaired removal of erythrocytes)
o Obstruction of gall bladder (less bile secretion)
o Damaged erythrocytes
Consequences
o Yellow skin and sclera, itchiness, pale stools, darkened urine

Explain unique features of cardiac muscle
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Myogenic – contracts without CNS stimulation
Branched cells – fast signal propagation and contraction in 3 dimensions
Cardiac muscles not fused, but connected by gap junctions – intercalated discs
More mitochondria – more reliant on aerobic respiration than skeletal muscle
Longer period of contraction and retraction for heart beat
Does not fatigue – continuous, life-long contractions
Interconnected network of cells is separated between atria and ventricles –
independent contraction

Explain cardiac contraction and heart sounds
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Cardiac muscles not fused together
Intercalated discs
o Each cell capable of independent contraction
o The coordinated contraction of cardiac muscle cells is controlled by
pacemakers
Atrial
o SA node – primary pacemaker – sends out electrical signals which are
propagated throughout atria via gap junctions
o Cardiac muscle contracts simultaneously (atrial systole)
o Connective tissue between atria and ventricles function to anchor heart
valves and cannot conduct electrical signals
o Signals form SA node must be relayed via AV node – this propagates signals
more slowly than SA – delay in passing on of the signal
o This delay optimises flow of blood between chambers
o Allows for blood to fill ventricles before AV valves close
Ventricular
o Occurs following excitation of AV node
o AV node sends signals down septum down Bundle of His
o Bundle of His innervates Purkinje fibres in ventricular wall – cardiac
muscle contracts
o Contractions begin at apex – blood forced up toward arteries
Diastole
o Period of insensitivity – relatively long – allows for passive refill between
beats
o Long recovery period helps prevent heart tissue becoming fatigued – lifelong contractions

Discuss heart disorders and treatments
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Hypertension – abnormally high blood pressure (systolic/diastolic/both)
Causes: sedentary lifestyle, salt/fat rich diets, alcohol, tobacco
o Can be secondary to other conditions e
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kidney disease or meds
o Does not cause symptoms itself, but in long term leads to narrow vessels
Thrombosis – formation of clot in blood vessel – occurs in damaged arteries due to
atherosclerosis – atheromas reduce vessel diameter (hypertension)
o High blood pressure damages wall – lesions – atherosclerotic plaques – if
plaque ruptures – clot – thrombus restricting blood flow – if thrombus
dislodged, can cause blockage – heart attacks or strokes
Coronary Heart Disease – condition caused by build up of plaque in coronary
arteries – consequence of atherosclerosis
o Risk factors: age, genetics, obesity, disease, diet, exercise, sex, smoking

Discuss steroid and peptide hormones
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Steroid
o Lipophilic – can freely cross plasma membrane
o Bind to receptors in cytoplasm or nucleus
o Form active receptor-hormone complex
o Activated complex moves into nucleus
o Binds to DNA – acts as transcription factor for gene expression
o E
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gs: insulin, glucagon, leptin, ADH, oxytocin

Discuss the process of lactation
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Production and secretion of milk by maternal mammary glands
Controlled by oxytocin and prolactin
o Prolactin secreted by anterior pituitary in response to PRH from
hypothalamus
o Develops mammary glands and production of milk
o Effects inhibited by progesterone which prevents milk production from
occurring prior to birth
Oxytocin is responsible for the release of milk from the mammary glands
o Produced in the hypothalamus and secreted by neurosecretory cells that
extend into posterior pituitary
o Triggered by stimulation of sensory receptors in breast by suckling infant
o Positive feedback loop – results in continuous oxytocin secretion until
feeding ends

Outline iodine role
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Thyroxin contains iodine in chemical structure
o Cannot be produced if iodine is deficient in the diet
o Iodine deficiency therefore affects thyroid gland
o Affects thyroxin production
Iodine deficiency will develop enlarged thyroid gland - goitre

Discuss high altitude training
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At high altitudes air pressure is lower – lower partial pressure of O2
Makes it more difficult for haem to take up and transport O2
Respiring tissue receives less o2 – headaches, fatigue, rapid pulse
Adaptations
o More erythrocytes / higher haem count with higher affinity / higher vital
capacity / more myoglobin and more vascularisation / kidneys produce
alkaline urine / greater lung SA and larger chest size

Discuss emphysema and treatments
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Walls of alveoli lose elasticity – abnormal enlargement of alveoli – lower total
surface area for gas exchange
Holes – bullae
Cause – smoking – chemical irritants damage walls – phagocytes – elastase –
breaks down elastic fibres (can be genetic)
Treatments:
o Bronchodilators / corticosteroids / elastase enzyme inhibitor / o2
supplementation / surgery / lung transplant

Explain the o2 dissociation curve, fetal haem and the Bohr shift
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Haemoglobin – four pp chains – each with heme group that binds O2
o As each O2 binds, conformation of haem altered – cooperative binding
o Haem has higher affinity for O2 in oxygen rich areas, promoting O2
loading
o Lower affinity in O2 starved areas – promoting oxygen unloading
Dissociation curve – relationship between oxygen levels and haem saturation
o Adult – sigmoidal – coop – low saturation of haem when o2 levels low
o High saturation of haem when o2 levels high
Fetal – higher affinity for o2 – curve left
o Fetal haem will load o2 when adult unloads
o Following birth, fetal haem replaced by adult haem within 6 months
o Fetal haem can be pharmacologically induced e
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for sickle cell anaemia
Myoglobin – o2 binding molecule in skeletal muscle
o Single pp chain – no coop binding – logarithmic not sigmoidal
o Higher affinity for o2 than adult haem
o Saturated at lower o2 levels – will hold onto its o2 levels until levels in
muscles are very low
o Delayed release helps to slow onset of lactic acid formation
Bohr shift – pH changes alter affinity of haem for O2
o CO2 lowers pH – causes haem to release O2 – shifts curve right
o Cells with increased metabolism release more CO2 – haem promoted to
release O2 at regions of greatest need
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40,000 primary oocytes
o Continues at puberty according to menstrual cycle
o Ends when hormonal changes prevent further continuance of cycle (menopause)



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