UNIT 1 - BIOLOGY AND DISEASE -revision
points
All the bullet points in this handout have been awarded a mark on A level
mark schemes at some stage. This handout shows the level of information you
must give in your answers and what the examiners are looking for.
General
You will in the exam get questions on unfamiliar topics! This is so
you can apply principles you have learnt into novel situations.
Components of a Triglyceride
• Phosphoric acid/phosphate
• Glycerol
• Fatty acid
What is a polymer?
• A long chain of MANY monomers. (this can be applied to
amino acids (polypeptides) or glucose (starch). Use the word MANY.
Which bond joins 2 monosaccharides ?
• Glycosidic
Disaccharides
Sucrose = Glucose + Fructose
Maltose = Glucose + Glucose
Lactose = Glucose + Galactose
(all have formula C12H22O11)
Test for non-reducing sugars
• test for reducing sugar first;
• boil/heat with acid;
• neutralise with alkali/sodium hydrogencarbonate;
• heat with Benedict’s (solution);
• blue to orange colour change indicates non-reducing sugars
Test for protein
• Add biuret
• Positive result – purple.
Protein Structure
Primary structure is the ORDER of the amino acids in a polypeptide chain
joined by hydrogen bonds.
Secondary structure is the coiling and folding of the primary structure into
an alpha helix and beta pleated sheet joined by hydrogen bonds.
Tertiary structure is the folding into a 3d shape joined by hydrogen ionic
and covalent bonds
Quaternary structure
is 2 or more polypeptide chains.
Test for lipid
• Add ethanol – shake and dissolve.
• Decant into water
• Positive result is an emulsion.
Microscropy
• Electron microscope has greater resolution (can distinguish
between objects close together)
• Because wavelength of electron beam smaller
Differences between prokaryotic and eukaryotic
• Eukaryotic ribosomes denser/heavier (not just ‘larger’)
• Eukaryotes have membrane bound organelles
• Eukaryotes have a nuclear membrane
• Prokaryotes have circular DNA
• Prokaryotes have a cell wall made of peptidoglycan.
Preparing a sample of organelles
• Homogenise;
• in ice cold;
• isotonic solution;
• Maintain concentrations/water potential same inside and
outside
• prevent osmosis;
• Prevent bursting/shrinkage organelles (not cells)
• then centrifuge
Structure of the membrane
• Phospholipids and proteins
• Phospholipid bilayer
• Arrangement of phospholipid molecules ‘tails to tails’
• ”Floating protein molecules”/molecules can move in membrane
• Intrinsic proteins extend through bilayer
• Extrinsic proteins in outer layer only
• Detail of channel proteins/glycoproteins
Osmosis
• The net movement of water particles from a high to low
water potential through a partially permeable membrane.
•
Facilitated diffusion
• Movement from high to lower concentration
• Use of carrier/channel protein
• Proteins specific
• Changes shape of protein and passes through channel/membrane
• No energy/ATP needed
Active transport
• Movement against concentration gradient
• Use of carrier/intrinsic/pump proteins
• Protein specific (to ion)
• ATP required (not just energy)
• Energy used to change shape of proteins/attach ion to
protein
• Ions moved through membrane as proteins change shape/position
• Moves substances against concentration gradient
Differences between active transport and diffusion
Active transport Diffusion
May move substances against concentration gradient;
Requires ATP/energy;
Requires membrane proteins/carriers Substances moved down
concentration gradient;
Does not require ATP/energy;
Does not (necessarily) require membrane proteins/carriers
Definition of a tissue
• Cells all the same/similar structure/function
Mechanism of enzyme action
• Activation energy reduced;
• Substrate attached to active site/formation of enzyme-substrate
complex;
• Less energy required to bring (substrate) molecules together/to
break bonds;
• Reaction occurs in small(er) steps;
• Change in shape of enzyme molecule (induced fit) brings
molecules together/allows bonds to break/causes overlapping of electron orbits
of substrates.
Loss of enzyme activity at high temps
• Enzyme (molecules) denatured at 60°C/high temperature,
or description of denaturing (eg vibration disrupts enzymes);
• Change (in shape) of active site;
• Change in tertiary/’3D’ structure/hydrogen bonds broken;
• Substrates no longer fit.
Effect of temperature increase on enzyme reductions
• Rate of reaction increases;
• Increasing temperature increases rate of movement of
molecules/kinetic energy;
• Collide more often/substrate enters active site more
often/more enzyme-substrate complexes formed;
• Up to optimum;
• Rate of reaction decreases;
• High temperatures cause denaturation/loss of tertiary
structure/3D structure;
• By breaking specified bonds (not peptide bond);
• Active site altered/substrate cannot bind/fit/
Non competitive inhibition
• Inhibitor is a different shape to substrate;
• Blinds at position other that active site/allosteric
site:
• Alters shape of active site;
• Substrate cannot bind/enzyme-substrate complex not formed;
Competitive inhibition
• Molecules compete for same active site;
• Molecules similar shape (not same)/both complementary
to/both fit active site;
• Prevents/slows production products;
Effect of pH on enzymes
• Small changes in pH affect charges on active site.
• Substrate does not bind as well.
• Large changes denature enzyme.
• By breaking hydrogen/ionic bonds in tertiary structure.
• Changing shape of active site
• No e-s substrate complexes are formed.
Substrate concentration
• Low substrate concentration, substrate limits the rate
of reaction.
• Due to free active sites
• High substrate concentration active sites limit rate
of reaction
• As all active sites are occupied.
Digestion of starch overview
Starch Maltose Glucose
Features of the human gas exchange system
• Large surface area (for diffusion);
• Thin alveolar wall/one cell thick/only 2 cells (from
air to blood);
• Detail – eg flattened cells in alveolar/capillary wall;
• Ventilation (of alveoli) keeps oxygen concentration low;
Flow/circulation of blood keeps oxygen concentration
• Maintains diffusion gradient/short diffusion pathway
How humans achieve efficient gas exchange
• One cell thick/thin (not thin membrane)/flattened cells
for faster diffusion/shorter diffusion pathway;
• Large surface area for faster diffusion;
• Ventilation to maintain a diffusion/concentration gradient;
Breathing In
• Diaphragm contracts and flattens
• External intercostals muscles contract and move up and
out
• Volume of thoracic cavity increases
• Pressure of thoracic cavity decreases
• Air moves in from high to low pressure.
Emphysema
• Damge to elastic tissue
• Reduces pulmonary ventilation
• Reduces concentration gradient.
• Less oxygen diffuses into the blood.
• Less SA:Vol
• Less oxygen for aerobic respiration
Pulmonary fibrosis
• Scarring of epithelium
• Increases distance of diffusion
• Decreases rate of diffusion of oxygen into blood
• Less oxygen for aerobic respiration
• Chronic dry cough
• Weakness and fatigue
Asthma
• Allergens
• Bronchioles become inflamed
• Secrete more mucus
• Muscle around bronchioles contracts
• Wheezing
• Coughing
TB
• Bacterium is spread in droplets of mucus/water when somebody
coughs/sneezes.
• Coughing of blood
• Fatigue
• Older/homeless/AIDS sufferes most at risk
• Treated by antibiotics –prevented by vaccination
• Some strains are becoming resistant.
Control of the heart cycle
• (cardiac) muscle is myogenic;
• sinoatrial node/SAN;
• wave of depolarisation/impulses/electrical activity (across
atria);
• initiates contraction of atria
• atrioventricular node/AVN causes a delay;
• bundle of His/purkyne tissue spreads impulse across ventricles;
ventricles contract after atria/time delay enables ventricles to fill;
Role of the SAN
• Emits wave of depolarisation/impulses/pacemaker/initates
beat; causing contraction of atria;
What causes an aneurysm
• Fatty deposits
• Narrow artery
• Increase pressure
• Damage artery wall
• Causes swelling / haemorrhage/burst
What causes an atheroma
• LDL’s transport and deposit cholesterol in (coronary)
arteries
• Narrow lumen/decrease blood flow
• Risk of clots
What causes myocardial infarction
• Fatty deposits in coronary artery
• Narrow artery
• Reduce blood flow / increase pressure
• Blood clots may block artery
• Less oxygen reaches heart muscle
Smoking
• Carbon monoxide combines with haemoglobin
• Reduces oxygen carrying capabilities
• Increased blood pressure
• Reduces oxygen reaching heart muscle.
• Nicotine increases risk of clots.
How is cholera spread
• Bacterium is spread in water contaminated with feaces
which is INGESTED
Cholera
• Caused by a bacterium
• Effects are diarrhoea / dehydration
• Cholera causes ion channels to open in epithelial cells
if the small inteatine
• Ions diffuse out and lower water potential of lumen
• Water leaves epithelial cells by osmosis
• Moving from high to low water potential
• Treatment ORT (glucose/starch,sodium,water)
• Glucose and sodium are taken in by facilitated diffusion
• Glucose required to synthesise ATP
Non-specific response
• Respond the same to any pathogen
• Physical barriers e.g. Skin
• Mucus in lungs traps pathogens
• Cilia sweeps out mucus
• HCl in stomach
Phagocytosis
• Whites blood cells engulf pathogen
• Form phagosome
• Fuses with lysosomes
• Enzymes digest the pathogen
Humoral immunity
• Antigen presentation
• Complementary receptor on T cell bind
• T cell divides by mitosis
• T cell may become killer cells,memory cells,helper cells,suppressor
cells.
Cell mediated immunity
• Antigen presentation
• B cells with complementary receptor binds to antigen
• T cells with complementary receptors binds to antigen.
• Helper cells stimulate B – cells to clone
• By mitosis
• Some become plasma cells and make antibodies
• Some become memory B-cells.
Monoclonal antibody
• Lymphocytes are fused with tumour cells
• Produce large quantities of a single type of antibody
• Can be used to target cancer cells
• Pregnancy tests
Antibodies
• A protein that is produced by lymphocytes
• During an immune response
• They are specific and complementary to antigens
Antigens
• A protein on the cell surface membrane
• That triggers an immune response
Vaccination
• Injection/oral administration of
• Antigens/dead pathogens/attenuated pathogens
• That stimulates the immune system to produce antibodies