AS Biology 1 Full Unit Biol1 Flashcards

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  • Created on: 18-05-14 12:55
What is a pathogen?
A disease-causing microorganism
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What is a disease?
Symptoms displayed following infection or malfunction
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What causes an infectious disease?
The transmission of bacteria, virus, or fungi from one host to another
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What is an interface?
A boundary between two systems
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How does a pathogen cause disease?
Gain entry to colonise host tissues, release toxins, damage cells, resist defences
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Name an example of Horizontal Transmission
Herpes - spread sexually through direct contact, can be through kissing (oral)
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Name a disease transmitted through water
Typhoid or Cholera
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Some diseases arise from the food that we eat. Name two.
Food poisoning - E-coli, Salmonella
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Vectors like animals pass on diseases. Name one.
Malaria, through mosquito
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The body has three main interfaces: skin, digestive system, and respiratory system. Explain their functions.
Respiratory - Mouth and Nose - Tuberculosis, Influenza. Digestive - Food and Water - Salmonella, Dysentery. Skin - Open wounds - AIDS
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The skin is the body's main line of defence. How does it protect us?
Platelets clot blood, white blood cells attracted to open wounds, sweat and oils are antiseptic. Acts as a barrier.
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The gas exchange system defends our body also, but how?
Mucus secreted, traps pathogens. Cilia moves them along and up trachea so they can be swallowed into the stomach and digested
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In the digestive system, how are we protected from pathogens?
Friendly bacteria, acidic pH to denature pathogens' enzymes, antiseptic mucus
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Tears often fill our eyes when we are under attack from a pathogen. Why?
Tears contain lysosomes with enzymes in to destroy bacteria
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How does CHD work?
Artery serving the heart's bloodflow becomes blocked. Cholestrol is deposited beneath the endothelium and an atheroma forms. Therefore, the atheroma restricts the blood flow.
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What are the risk factors for CHD?
Age, sex, physical activity level, HDL in diet, high blood pressure, smoking, cholestrol level, obesity, diet
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How does Cancer unfold?
Uncontrolled cell division leads to a gene mutation, responsible for normal cell division, tumour forms
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Name some risk factors for cancer.
Smoking, UV exposure, Diet (Fibre), Age, Physical activity, Sex, Genes
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What happens in Physical Breakdown?
Teeth break down food in mouth, provide large SA for chemical digestion, stomach muscles churn food up
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What happens in Chemical Digestion?
Enzymes break large insoluble molecules into smaller ones. Function by hydrolysis - enzymes are hydrolases.
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Absorbed and assimilated...
small components can be assimilated into the larger ones after being absorbed into the small intestine
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What is the function of the oesophagus?
Food taken through tube to stomach from mouth using muscle contractions called Peristalsis. Mucus lubricates food and kills pathogens.
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What is the function of the stomach?
Muscles contract to churn food, gastric juice creates low, acidic pH with pepsin and HCl to denature enzymes
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Small intestine's function?
Absorption of soluble food, digestion of protein, fat, carbohydrate by enzymes produced in walls, villi increase SA
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What is the function of the large intestine?
Absorbs water, removes insoluble food, folded for large SA
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If a body part received stool from colon and stored faeces, which one would it be?
Rectum
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What are the functions of the liver and the pancreas?
Liver - produces bile to neutralise the stomach and break down fat, Pancreas - releases pancreatic juice with all enzymes necessary for food breakdown contained in it
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What is a monosaccharide?
Basic monomer unit - a sugar.
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Name two features of a monosaccharide and give its general formula.
Monosaccharide - sweet-tasting, soluble. (CH2O)n
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Give three examples of monosaccharides.
Glucose, Fructose, Galactose.
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To test to see if monosaccharides are present in food, we do a test called the Benedict's Test for Reducing Sugars. Explain it.
1. 2cm³ of food sample in liquid form (grind up with water) to 2cm³ Benedict's Reagent (Copper II Sulphate). 2. Heat for 5 minutes in a gently boiling water bath. 3. Positive result = brick red precipitate of copper oxide.
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When two monosaccharides join, they make a disaccharide. How do they join together?
Condensation reaction - removal of 1 molecule water - forms a glycosidic bond between monosaccharides
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Name three disaccharides.
Maltose (glucose + glucose), Lactose (glucose + galactose), Sucrose (glucose + fructose)
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The reaction to make disaccharides is reversible. What is the reaction called to break up a disaccharide into its constituent monosaccharides?
Hydrolysis
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We can also test to detect if disaccharides are present in food through a test for non-reducing sugars. Explain this test.
Neg result of Reducing Sugar test = stays blue. Add 2cm³ HCl to food sample to hydrolyse, add sodiumhydrogen carbonate to neutralise (Benedict's Reagent doesn't work in acidic conditions), check with pH paper. Retest with Reducing Sugar test.
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Polysaccharides are...
Large, insoluble polymers which can be hydrolysed.
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How do they form?
Glycosidic bonds between monosaccharides from condensation reactions
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Give three examples of polysaccharides.
Starch, glycogen and cellulose. Used for energy, storage, and support.
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How do we test for Starch?
Add drops of Iodine to food sample, shake. Blue-black colour change indicates starch
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Describe amino acid structure.
Central carbon atom with four groups joined on. NH2 - amino group. COOH - carboxyl group. R - R group, specific to each amino acid. H - Hydrogen atom
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How do peptide bonds form and what do they do?
Form from condensation reactions - removes one H from NH2 and the OH from COOH, so they join amino acids together by the Nitrogen (N) and the Carbon (C)
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Describe the primary structure of a protein.
Unique, specific order/sequence of amino acids
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Describe the secondary structure of a protein.
Amino acids twisted into 3D coils called alpha helices, held together by hydrogen bonds
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Describe the tertiary structure of a protein.
Complex twisted distinctive 3D structure held together by hydrogen, ionic and disulphide bonds
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Describe the quaternary structure of a protein.
Several polypeptide chains associated together with prosthetic groups
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Name the test for proteins. How does it work?
Biuret Test - add Biuret (sodium hydroxide and copper sulphate) to food sample (ground up) and if there is a violet/purple colour change then peptide bonds are present
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How are proteins adapted to be receptors?
Variety of proteins = variety of primary structures. Allows distinctive, specific active site formed from tertiary structure, which allows formation of receptors from ES complexes in binding site.
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Fibrous proteins - give two examples.
Collagen in tendon/bone, keratin in hair.
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The fibrous proteins are formed from...
Sheets for flexibility and fibres for strength
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How are fibrous proteins insoluble? How do they withstand tension?
Insoluble - external R group are non polar. Withstand tension - Hydrogen bonds create cross linkages for withstanding tension.
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What are enzymes?
Biological catalysts which speed up a reaction by lowering the activation energy and allowing it to continue at a lower temperature
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Describe the enzyme lock and key hypothesis.
A lock only has one key, so an enzyme only has one substrate. The substrate is considered to fit the active site of the enzyme perfectly, which explains its specific shape. Suggests that the AS is rigid, but scientists say it is flexible.
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The proposed "flexibility" of the active site has led to the Induced Fit Model. Explain it.
Active site is like a glove - moulds itself around the substrate. Substrate disturbs enzyme's natural shape, as enzyme changes shape it puts strain on the substrate, distorts bonds, lowers activation energy needed to break said bond
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Why is the Induced Fit model better than the Lock and Key?
Explains how other molecules can affect an enzyme, explains how activation energy is lowered
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Describe what would happen in an enzyme controlled reaction if there was a rise in temperature.
More kinetic energy - faster molecule movement - more collisions - more ES complexes formed
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What happens if the temperature goes beyond 40 degrees?
Hydrogen bonds break, shape distorted and changes, substrate no longer complementary/can no longer fit, fewer ES complexes made, slower rate. At 60 degrees the enzyme denatures.
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What happens if there is a change in pH in an enzyme controlled reaction?
Changes charges on active site, breaks bonds (hydrogen etc) making up tertiary structure. Shape of active site changes, enzyme changes shape, enzyme denatured as no ES complexes made
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If there is a low substrate concentration in an enzyme controlled reaction...
Lots of empty active sites, reaction at half of maximum
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At medium concentration in an enzyme controlled reaction...
all active sites are full and the reaction is at its highest/most efficient rate
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At a high concentration in an enzyme controlled reaction...
There is an excess of substrate and the reaction hits the Vmax as all the active sites are filled and the excess has no further effect
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Describe how a competitive inhibitor affects an enzyme controlled reaction.
Similar shape to substrate - binds at active site temporarily. Depends on concentration of substrate/inhibitors - if there are more inhibitors they compete for the active site. Eventually all substrates bind so competitive inhibitors decrease ROR
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Non-competitive inhibitors - how do they affect a reaction?
Attach to a point on the enzyme which is not the active site - distort bonds, changes shape of active site - substrate no longer complementary - no ES complexes made
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What is a limitation of a light microscope?
Wavelength is too long
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List 3 advantages of a TEM.
Small object seen, high resolution, shorter wavelength
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Card 3

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What causes an infectious disease?

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Card 4

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Card 5

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How does a pathogen cause disease?

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