Enzymes are biological catalysts

Enzymes

Catalysts speed up chemical reactions

They do this by lowering the energy needed to make the reaction take place

Factors affecting the activity of an enzyme

Enzyme activity is affected by;

1. Temperature

2. pH

3. Enzyme concentration

4. Substrate concentration

5. Inhibitors

High temperatures cause chemical bonds to break – the shape of the active site changes and the substrate can no longer bind to it. The enzyme has been denatured.

substrate bound to active site

enzyme denaturedenzyme

5. Inhibitors

An inhibitor is a substance which slows down or stops the activity of an enzyme.

There are two types of inhibitor:

•Competitive

•Non-competitive

no inhibitor

competitive inhibitor

non-competitive inhibitor

Increasing substrate concentration

Rate of reaction

Comparative effects of increasing substrate concentration in the presence of inhibitors when enzyme concentration is limited

Competitive inhibitor – rate of reaction is affected by

concentration of inhibitor and substrate

Non – competitive inhibitor is affected by concentration of inhibitor only, increasing concentration of substrate

has no effect.

Protein synthesis -- translation

The ribosome reads the codons on the mRNA and uses the information to make protein

ribosome

mRNA

amino acid

tRNA

codon

GUAanti-codon

protein under construction

peptide bond

Codes

G T C A G G A T T C G G A C A

DNA

C A G U C C U A AG C C U G U

mRNA

G U C A G G AU UC G G A C A

tRNA

6C Glucose

3C Pyruvic acid

2C Acetyl co-enzyme A

4C compound 6C Citric acid

(Tricarboxylic acid)

ATPCO2

Hydrogen

(waste product)

(picked up by NAD)

glycolysis(cytoplasm)

Inside matrix of mitochondrion

Respiration

ATP and Muscle Contraction

The following experiment shows that ATP provides the energy for muscle contraction, and not glucose

Glass slide

Muscle fibres

1% glucose 1% ATP Water(control)

Final measurements were taken after 5 minutes to allow time for uptake of the solutions

Results

Solution

glucose

ATP

water

decrease % difference

Initial length

Final length

18mm

21mm 21mm

18mm

0mm

2mm

0mm 0

0

% increase = ( decrease x 100) Initial length

= 2 x 100 20

= 10%

20mm

18mm

10%

Only ATP caused muscle contraction, so it must be ATP that supplies the energy for muscle contraction

Protein Secretion

Nuclear membraneRough endoplasmic reticulum

Ribosomes

Golgi apparatus

Ribosomes --where protein is madeRough endoplasmic reticulum (RER) – transports proteinGolgi apparatus – packages protein for secretion

Secretion of protein from a cell is an example of Exocytosis.

The effect of osmosis on red blood cells

Same water concentration No change

Lower water concentration

(crenated)

Shrink + wrinkle

Burst(Haemolysed)

Higher water concentration

Antibodies

Antibodies are Y-shaped molecules produced by lymphocytes.

Receptor sites

The function of the receptor sites is to combine with antigens

0 10 20 30 40 50 60

Time (days)

Concentration of antibody in blood

First injection of vaccine

Second injection of vaccine

Second response is ; 1.faster

2. more antibodies are made

Genetics

The normal human body contains 22 pairs of autosomesIn addition, we have 2 sex chromosomes;

males = XY

females = XX

This gives us a total of 46 chromosomes

Some individuals may have 45 (Turner’s syndrome), or 47 (Klinefelter’s syndrome / Down’s syndrome)

This occurs due to a chromosomal mutation called Non - disjunction

Example of a monohybrid cross ;

The gene for tongue rolling in humans has two alleles.

Roller (R) is dominant over non-roller (r) which is recessive If a woman who is homozygous for tongue rolling marries a man who is homozygous for non-rolling then;

P phenotypes female roller X male non-roller

genotypes RR X rr

gametes R r

F1 genotype of children Rr

All rollersF1 phenotype of children

If a woman who is heterozygous for tongue rolling marries a man who is homozygous for non-rolling then;

P phenotypes female roller X male non-roller

genotypes Rr X rr

gametes R + r All r

F1 genotype of children Rr rr

F1 phenotype of children 50% are rollers + 50% are non-rollers

If both parents are heterozygous then ;

P phenotypes female roller X male roller

genotypes Rr X Rr

gametes R + r R + r

F1 genotype of children

F1 phenotype of children

RR Rr Rr rr

75% are rollers and 25% are non-rollers

Line Graphs

Always label axes fully, do not abbreviate.Choose a scale that uses as much of the graph paper as possible and allows you to plot the numbers accuratelyA scale has equal divisions

Your scale must extend beyond the line you draw

Always label your origin

Always join up your points using a ruler

Do not extend your line beyond the points given eg .do not draw to 0 if you have not been given a value for 0

0 2 4 6 8 10 12 14

0

10

20

30

40

50

Time (minutes)

Volume of oxygen produced (cm3)

x

xx

x

xx x x