Biology Unit 1

What 4 things must a microorganism do to be considered a pathogen?

1. Gain entry to the host, 2.Colonise the tissues of the host, 3. Resist the defences of the host, 4. Cause damage to the host tissues

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Which two systems are common sites of entry for pathogens?

The digestive and respiratory systems.

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How do pathogens cause disease?

By damaging host tissues or by producing toxins.

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Give 3 examples of natural bodily defences to prevent the entry of pathogens?

Mucous layer, production of enzymes that break down pathogens, stomach acid.

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Define correlation.

A change in one variable is reflected by a change in another. It is not a causal link/relationship.

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What do we consider when thinking about risk?

The probablity a hazardous event will occur and the consequences of the hazardous event.

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What are the lifestyle factors that contribute to cancer?

Smoking, diet, obesity, physical activity, sunlight.

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What are the lifestyle factors that contribute to CHD?

Smoking, high blood pressure, blood cholesterol, obesity, diet, physical activity.

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Give 3 differences between prokaryotic and eukaryotic cells.

Pro: no true nucleus, no nucleolous, no chromosomes (circular DNA strands), no membrane-bound organelles, no chloroplasts, smaller ribosomes (70s not 80s), no ER, golgi apparatus or lysosomes, cell wall made of peptidoglycan (as opposed to cellulose)

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Define: digestion.

The breaking down of large molecules by enzymes into smaller molecules which can be absorbed and assimilated.

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What adaptations does the stomach have for its function?

Muscular for churning food; inner layer that produces enzymes (particularly to digest protein); glands to produce mucus to protect lining from enzymes; stomach acid to kill pathogens in food; correct pH for stomach enzymes.

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Why is the lining of the small intestine folded into villi?

To give a large surface area for absorption.

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What enzymes are secreted by the pancreas?

Proteases, lipases and amylase.

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What are lipids broken down into during hydrolysis?

Glycerol and fatty acids.

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What type of monomer makes up the polymer starch?

alpha glucose (formula C(6)H(12)O(6)

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What is the name given to a pair of monosaccharides joined by a glycosidic bond?

A disaccharide.

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What is the test for reducing sugars?

Benedict's test: mix equal volumes of liquified sample and benedict's reagent; heat in a boiling water bath for 5 mins; colour change to green-red indicates presence of reducing sugars.

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What is the name of the reaction that forms glycosidic bonds?

Condensation (because of the production of water).

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How do we test for non-reducing sugars?

Add equal volumes of the sample and dilute HCl to a test tube; place in a hot water bath for 5 mins; add some NaOH to neutralise the solution (test for neutral with litmus paper). Retest sample with Benedict's: colour change=a non-reducing sugar.

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Which monomer units make up a) Lactose and b) Sucrose?

a) glucose and galactose, b) glucose and fructose

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What is added to food to allow enzyme function in the small intestine?

Bile (to neutralise stomach acid).

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What enzyme is secreted by the epithelial lining of the small intestine?

Maltase.

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What causes lactose intolerance?

A person not producing enough lactase to break down all the lactose they consume.

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What happens to undigested lactose in the large intestine?

It is broken down by microorganisms, resulting in the production of large volumes of gas.

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How can lactose intolerance be treated?

Avoiding lactose-containing products, or adding lactase to lactose products before consuming.

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What type of molecule are enzymes?

Proteins.

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Amino acids are monomers. What chemical groups do they contain?

A central C atom is attached to an amino group (-NH(2)), a carboxyl group (-COOH), a hydrogen atom (-H) and an R group.

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What determines the type of amino acid?

The R group.

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What type of bonds are formed when amino acids join together, and in what type of reaction?

Peptide bonds in a condensation reaction.

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What type of bonds do polypeptide chains form in the secondary structure?

Hydrogen bonds. These twist and fold the protein into alpha helixes and beta pleated sheets.

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Which bonds maintain tertiary structure of proteins?

Disulphide bonds (strong), ionic bonds (broken by pH changes), hydrogen bonds (fairly weak).

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What determines the function of a protein?

Its 3D shape.

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What parts make up the quaternary structure?

A number of polypeptide chains, and associated non-protein (prosthetic) groups.

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What is the test for proteins and how is it performed?

The Biuret test. Add equal volumes of the sample and NaOH to a test tube; add a few drops of very dilute copper sulfate solution. Blue-no peptide bonds (ie no proteins), purple- peptide bonds present.

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What are the functions of a) fibrous and b) globular proteins?

a) structural functions, b) metabolic functions

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Where is collagen (a fibrous protein) found?

In tendons.

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How can we accurately define enzymes?

Globular proteins that act as biological catalysts.

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What is the function of a catalyst?

To lower the activation energy (the minimum amount of energy required to activate a reaction) of a reaction.

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What is the functional area of an enzyme known as?

The active site.

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What is formed during enzyme-catalysed reactions?

Enzyme-substrate complexes.

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Describe the lock and key model.

http://upload.wikimedia.org/wikibooks/en/b/b9/Lock-and-key_model.JPG

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How is the induced fit model different to the lock and key model?

It suggests the enzyme changes shape to fit the profile of the substrate.

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How does the induced fit model suggest the enzyme catalyses the reaction?

The enzyme puts pressure on the bonds to be broken in the substrate as it changes shape.

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What factors affect enzyme action?

Temperature, pH, concentration of enzyme/substrate, presence of an inhibitor.

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How do we measure the rate of a reaction?

By measuring either the rate of the formation of the products or the rate of the disappearance of the substrate.

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What is denaturation?

A permanent change that affects the structure of a protein such that it cannot perform its function.

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What effect does temperature have on enzyme action?

Increased RoR as temperature approaches optimum due to increased kinetic energy of the molecules, after optimum, RoR decreases due to H bonds in enzyme beginning to break.

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What effect does pH have on enzyme action?

Increased RoR as pH approaches optimum, after optimum, RoR decreases. Above or below the optimum pH some or all enzymes may be denatured by the breaking of ionic bonds.

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What is the difference between competitive and non-competitive inhibitors?

Competive inhibitors have a molecular shape similar to that of the substrate so occupy the active site, whereas non-competitive inhibitors bind to a site that is not the active site.

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How do competive inhibitors recuce the RoR?

By occupying the active site and thus preventing the formation of an enzyme-substrate complex.

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How do non-competive inhibitors recuce the RoR?

By changing the shape of the enzyme molecule so the substrate molecule cannot fit into the active site in a way that allows the reaction to proceed.

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How can we overcomecompetitive inhibitors?

By increasing substrate concentration.

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How can you calculate magnification?

size of image/size of object

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How many micrometers in a millimetre?

1000

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Define: resolution

The minimum distance apart two objects can be for them to appear as separate items.

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What is cell fractionation?

The process whereby cells are broken up and organelles separated out.

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In what type of solution must cells be kept?

Cold (to reduce enzyme action), isotonic (to prevent swelling or bursting) and buffered (to maintain constant pH)

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What are the stages of cell fractionation?

Homogenation, filtration and ultracentrifugation.

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Describe the process of homogenation.

Cells are broken up in a homogeniser (effectively a blender) to release individual organelles. This produces a homogenate which must be filtered.

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How does ultracentrifugation work?

The homogenate is spun in an ultra centrifuge. The heaviest organelles (nuclei) form at the bottom of the tube at the lowest speed, and can be removed. The process is then repeated at progressively higher speeds to remove lighter organelles.

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What are the 3 types of microscope?

Light, transmission electron and scanning electron

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Why do the electron microscopes have a high resolution?

The beam of electrons has a short wavelength.

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What condition must the specimen be in for electron microscopes?

Near vacuum, and stained/impregnated with heavy metals. The specimen must also be very thin for the TEM.

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Give two advantages and two disadvantages of light microscopes.

Ads: colour image, easy to prepare slide, living specimens can be observed, no artefacts to distort image. Disads: low resolution and low magnification, individual organelles not visible.

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What are the components of the nucleus?

Double outer membrane called the nuclear envelope, with nuclear pores to allow passage of large molecules. Contains nucleoplasm- a jelly-like material, chromatin (genetic material) and the nucleolus.

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What is the function of the nucleus?

Acts as control centre of the cell. Contains genetic material which codes for protein synthesis. Manufactures ribosomal RNA and ribosomes.

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Describe the structure of the mitochondria?

Double-membrane bound structure. Inner made up of folded membranes- cristae, and the space in-between them- the matrix.

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How does the structure of a mitochondrion relate to its function?

It has a large SA for attachement of respiratory enzymes to produce ATP. Matrix controls protein production.

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What is the difference between the rough and smooth endoplasmic reticulums?

Rough is a system of sheet like membranes whereas smooth is tubular. Rough has associated ribosomes and smooth doesn't.

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What is the function of the rough ER?

Protein synthesis and acts as a transport pathway for proteins.

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What is the function of the smooth ER?

Synthesise, store and transport lipids and carbohydrates.

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What are the two main components of the golgi body/apparatus?

Flattened sacs (cisternae) and hollow vesicles.

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Give 3 functions of the golgi body.

1) receive proteins and lipids from the ER. 2) add carbs to proteins to make glycoproteins. 3) secrete enzymes. 4) secrete carbohydrates. 5) transport, modify and store lipids. 6) manufacture lysosomes.

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What is the function of lysosomes?

Isolate and dispose of harmful enzymes. Break down material ingested by phagocytic cells. Digest worn out organelles. Completely digest cell after death (autolysis).

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Describe ribosomes.

Small cytoplasmic granules in the cytoplasm or associated with the RER.

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What are the two types of ribosomes and where are the found?

smaller 70s type in prokaryotic cells and larger 80s type in eukaryotic cells.

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What are ribosomes important for?

Protein synthesis.

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Give 3 properties of lipids.

Soluble in organic solvents e.g. ethanol. Insoluble in water. Smaller proportion of oxygen to carbon and hydrogen than in carbohydrates.

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Give 3 types of lipids.

Triglycerides, phospholipids and waxes.

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What is the difference between fats and oils?

Fats are solids at room temp and oils are liquid.

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Give 2 important functions of fats.

Energy source, waterproofing, insulation and protection.

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What type of lipid makes up plasma membranes?

phospholipids.

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Describe the structure of a phospholipid.

Phosphate molecule and two fatty acid molecules linked to glycerol.

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What is the test for lipids?

Add ethanol to sample and shake well to dissolve any lipid then add water. Change from clear to cloudy-white indicates presence of a lipid.

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What form do phospholipids take in a plasma membrane?

Bilayered sheet

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What is the difference between extrinsic and intrinsic proteins?

Extrinsic are on surface or partially embedded. Intrinsic span the bilayer.

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Give 3 functions of proteins in the membrane.

Mechanical/structural support, act as receptors in conjunction with glycolipids, help cells adhere together, transport water soluble substances and facilitate active transport.

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Which types of particle movement are passive?

Diffusion, facilitated diffusion and osmosis.

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What direction do passive particle movements take place?

Down a concentration/water potential gradient.

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What is Fick's Law?

Diffusion is proportional to surface area and conc. gradient and inversely proportional to the length of the diffusion pathway.

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Where does facilitated diffusion occur on the plasma membrane?

Via certain carrier proteins that change shape due to the presence of certain particles.

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What happens to a plant cell when the water potential outside the cell is lower than inside?

It becomes plasmolysed- the protoplast comes away from the cell wall.

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What are the two types of active transport?

Direct and co-transport.

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Describe the co-transport of sodium ions and glucose.

1) Sodium/Potassium pump actively transports Na+ out of cell into blood. 2) Low conc of Na ions in the cell means sodium coupled with glucose diffuses into the cell from the lumen of the small intestine. 3) Glucose diffuses into blood plasma.

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Describe bacterial cells.

No true nucleus or nucleolus. Circular strands of DNA (plasmids). No membrane bound organelles- chloroplasts, ER, golgi body, lysosomes. Smaller ribosomes (70s). Cell wall made of peptidoglycan.

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What is the function of the flagellum in the Vibrio cholerae bacterium?

To propel themselves through the mucus lining of the intestinal wall.

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What does the toxin produced by the cholera bacterium do?

One part binds to carb. receptors specific to small intestine. Other enters epithelial cell and causes Cl- channels to open.

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What is the effect of the Cl- channels in the small intestine opening?

Loss of Cl- ions from epithelial cells lowers water potential of lumen, causing water loss from the cells and in turn the blood.

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What symptoms does water loss due to the cholera bacterium give?

Dehydration and diarrhoea.

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What ingredients does a rehydration solution contain?

Water, sodium, glucose/starch, potassium and other electrolytes.

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Describe the structure of the trachea.

Flexible tube, with rings of cartilage which prevent it collapsing. Walls are lined with ciliated epithelial cells and goblet cells which produce mucus, which the ciliated cells then pass up the throat to the oesophagus.

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Describe the bronchioles

Branching divisions of the bronchi, made of muscle and lined with epithelial cells.

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How are the alveoli adapted for their function?

They contain elastic tissue which give them a large volume, and also allow them to expel air. The membrane is one cell thick so gives a short diffusion pathway. They give the lungs a large surface area for diffusion.

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What is the function of the intercostal muscles in inspiration and expiration?

Inspiration: internal IC muscles contract and external relax, pulling the ribcage upwards and outwards. Expiration: opposite.

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Do the diaphragm muscles contract or relax during inspiration?

contract

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How is pulmonary ventilation (dm3/min) calculated?

tidal volume x ventilation rate

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Why are the lungs an efficient exchange surface, with reference to Fick's law?

Alveoli give large SA and ventilation and constant blood flow maintain conc. gradient, both of which are proportional to rate of diffusion. Short diffusion pathway due to single cell membrane which is inversely proportional to rate of diffusion.

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Give some symptoms of TB

Primary infection: few symptoms. Secondary: coughing with blood/damaged lung tissue.

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How can the spread of TB be prevented/controlled?

Better education about the need to complete courses of antibiotics, better housing (not damp), improved heath facilities and treatments, better nutrition.

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Which lung disease affects a) ventilation by inhalation, b) surface area and c) length of diffusion pathway

a) asthma, b) emphysema and c) fibrosis

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What causes the symptoms of pulmonary fibrosis?

Scars forming on the epithelium of the lungs, perhaps due to microscopic lung injury.

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What is asthma?

A localised allergic reaction to allergens which vary from person to person eg. pollen, animal fur.

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What happens during an asthma attack?

Linings of airways become inflamed, large quantities of mucus are secreted, fluid leaves the capillaries and enters the airways, muscle surrounding the bronchioles contracts, constricting the airways.

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What is the main risk factor for emphysema?

smoking

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What effect does emphysema have on the alveoli?

Elastin is permanently stretched so air cannot be forced out from the alveoli properly. SA of the alveoli is reduced and they sometimes burst.

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Give the order of structures which blood passes through in the heart?

Vena cava, right atrium, (AV valve), right ventricle, (semi lunar valve), pulmonary artery, (lungs), pulmonary veins, (semi lunar valve), left atrium, (AV valve), left ventricle, (semi lunar valve), aorta.

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Why is the wall of the left ventricle thicker than the right/that of the atria?

It has to pump blood much further than any other structure, so more muscle is required.

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What supplies blood to the heart muscle?

the coronary arteries

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Why is there a delay between atrial systole and ventricular systole?

To allow the ventricles to fill

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What happens during diastole?

The atria and ventricles begin to fill. Low pressure in the ventricles causes the semi lunar valves to shut- the 'dub' sound.

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What is the function of valves?

To prevent the back flow of blood.

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How is cardiac output calculated?

heart rate x stroke volume

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What initiates the contraction of the cardiac muscle?

It is myogenic- it's contraction is initiated from within the muscle itself by the sinoatrial node.

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What causes the delay between atrial systole and ventricular systole?

The AV septum is a layer of non-conductive tissue which prevents the impulse from the SA node reaching the ventricles directly.

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What nodes/structures does the impulse pass through to initiate ventricular systole?

SA node, AV node, bundle of His, via AV septum to apex. (ventricles contract from apex up).

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What is atheroma?

A fatty deposit of white blood cells that have taken up LDLs- an atheromatous plaque.

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How can atheroma lead to thrombosis?

If an atheroma breaks through the lining of the vessel, a rough surface is formed. This interrupts the smooth flow of blood and can so cause a blood clot (thrombus).

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How can atheroma lead to an aneurysm?

Atheromas weaken the walls of an artery, and these weak points can swell to form a balloon-like pocket of blood, called an aneurysm. (If this bursts it can lead to haemorrhage.)

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Carbon monoxide makes smoking a risk factor for CHD, how?

CO combines irreversibly with haemoglobin to form carboxyhaemoglobin. This reduces the capacity of the blood to carry oxygen so the heart has to work harder. This increases blood pressure.

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What effect does nicotine have on the risk of developing CHD and why?

It increases the risk, as nicotine stimulates adrenaline production and thus increases blood pressure. It also makes blood platelets 'sticky', increasing the risk of thrombosis.

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Biology Unit 1

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