BIOL 1

AQA GCE BIOLOGY UNIT 1

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  • Created by: Alice
  • Created on: 14-05-11 15:09

CAUSES OF DISEASE

Pathogens cause disease by:

1. Produce toxins

2. Harm host tissues

enter body through; gas-exchange system / digestive system

To be considered a pathogen:

gain entry to host, colonise the tissues, resist defences, cause damage

Pathogens- Fungi, bacteria, viruses

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LIFESTYLE AND HEALTH

Risk factors and cancer:

smoking

diet

obesity

physical activity

sunlight

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Risk factors of CHD

smoking

High BP

blood cholesterol levels- fewer sat fats

obesity- lower BMI

diet- reduce salt intake to lower blood pressure

physical activity- lower BP

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ENZYMES AND DIGESTION

Oesophagus- thick muscular wall

Stomach, small intestine, large intestine, rectum, salivary glands, pancreas

Digestion- physical breakdown, chemical digestion

Carbohydrases- break down carbs

lipases- break down lipids (fats)

proteases- break down proteins (to amino acids)

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MONOSACCHARIDES

 a-glucose                             (http://t1.gstatic.com/images?q=tbn:ANd9GcQa6OzITE1nvyrf00GdBNbrg1TELR0JgXy-l9NcCgR5H0oAuiOY)      (http://t3.gstatic.com/images?q=tbn:ANd9GcTjpDyZj2j5WYZ6KN_D4yJVWwn7Ougzd8x2rnaJtpvm3vB88OGjDg)condensation reaction

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TESTS

reducing sugars- heat w/ benedicts reagent

will go orange/brown if present

non-redfucing sugars, heat w/ acid, then add benedicts reagent to hydrolyse into

monosaccharides breaking GLYCOSIDIC BOND

starch

iodene, if starch present -> blue/black

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Digestion of Starch

amylase,

hydrolyses starch into maltose;

breaks glycosidic bond;

maltose;

hydrolysed;

into glucose;

glucose absorped into blood

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LACTOSE INTOLERANCE

digested in small intestine, w/ lining epithelial covered in lactase

lactose= glucose+galactose

intolerant- the glycosidic bond is not hydrolysed by lactase

gas,nausea, cramps

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PROTEINS

  • peptide bond
  • primary-polypeptide- sequence of amino acids, change in sequence=change in protein
  • secondary structure- coiled polypeptide, H-bonds
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PROTEINS

  • Tertiary Structure- disulfide bonds-strong
  •                               ionic bonds- formed between carboxyl and amino groups                               H-Bonds- numerous but easily broken
  • more twisted and folded
  • Quaternary Structure- more than one polypeptide chain twisted together to form a molecule

Test for proteins

mix sample with Biuret reagent, will go purple if positive

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Enzyme action

(http://live.kerboodle.com/NT3/NTLS_RootRepository/ContentPackages/45/aqa%20as%20biology_scorm%202004_final_1/product/bio_as_ch02_pg32_fig3_lab.jpg)

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Enzymes as catalysts lowering activation energy

an initial boost of energy is needed to kick start the reaction, the min. energy required to do this is called the activation energy

Enzyme Structure;

active site

substrate

Enzyme- protein, globular, 3D shape based on amino acid sequence

enzyme-substrate complex

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LOCK AND KEY MODEL

(http://t3.gstatic.com/images?q=tbn:ANd9GcT5MbKNDpDBbJCqqy6PigpXyqA3T5QboWSMLiDObpuhM3chi5Lsrg)

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INDUCED FIT

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Factors affecting enzyme action

p.H- alters amino acid charges on active site, changing its shape, no enzyme-substrate complex can be formed, denatured, can also break the H-bonds in tertiary structure

temperature; increased kinetic energy, too high- denature

substrate concentration- too low, slow, too high, no difference, intermediate =optimum

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Competitive inhibitors

occupy active site as similar shape to substrate, therefore compete w/ substrate, greater the conc. of inhibitors, less enzyme-substrate complexes etc

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Non-Competitive inhibitor

(http://live.kerboodle.com/NT3/NTLS_RootRepository/ContentPackages/45/aqa%20as%20biology_scorm%202004_final_1/product/bio_as_ch02_pg36_fig2_lab.jpg)

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Microscopy

Magnification= size of image/ size of object

mm, to micro-m's = X 1,000

size of object= size of image/magnification

Resolution- higher resolution, clearer image

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Cell Fractionation

cold- reduce enzyme activity

isotonic- maintain water potential, prevent organelles bursting through osmotic movement

buffered- to maintain a constant p.H

Homogenation- break cell membrane- release organelles, filtered to remove debris

Ultracentrifugation- spun, 

1. heavy- nucleus , slow

2. mitochondria

3. ribosomes, fast, lighter in mass

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MICROSCOPY

TEM+ SEM

better than light microscopes as electrons have shorter wave length- higher resolution, clarity

TEM- vacuum (dead), B&W, thin specimen, artefacts

SEM- as above, less resolving power, 3D image

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Comments

abi

Your a life saver

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