Section 1

how is the substrate molecule held within the active site

by bonds that temporarily form between certain amino acids of the active site and groups on the substrate molecule

what is formed when the substrate neatly fits into the depression

an enzyme-substrate complex

what is the molecule on which the enzyme acts upon called

the substrate

what does the the active site form within the enzyme molecule

a small depression

what is an enzymes active site made of

a relatively small number of amino acids

what do enzymes do to the activation energy

lower it, allowing reactions to take place at a lower temperature than normal- why so many reactions can occur at 37°C which is low for chemical reactions

what is free energy

the energy of a system that is available to perform work

conditions for typical chemical reactions to take place

- substrates must collide with sufficient energy to alter the arrangement of their atoms to form the products

- the free energy of the products must be less than that of the substrates

- activation energy

a molecule with an uneven distribution of charge

polar molecule, polarised

what is the activation energy

the minimum amount of energy needed to activate the reaction

enzymes don't make reactions happen they

speed up reactions that already occur

what do catalysts do

alter the rate of a chemical reaction without undergoing permanent changes themselves. they can be reused repeatedly and are effective in small amounts.

what type of proteins are enzymes

globular proteins that act as catalysts

fibrous proteins structure

form long chains which run parallel to one another. these chains are linked by cross bridges, forming very stable molecules

cellulose biggest difference

beta glucose

globular proteins use

carry out metabolic functions

fibrous proteins use

have structural functions

buiret test method

- place a sample of solution in a test tube and add an equal volume of sodium hydroxide solution at room temp

- add a few drops of very dilute (0.05%) copper (II) sulfate solution and gently mix

- a purple colour indicates the presence of peptide bonds and therefore a protein

- if no protein is present in remains blue

what does the buiret test detect

peptide bonds

test for protein name

buiret test

in a hydrogen bond

the positive region and negative region attract forming a weak electrostatic bond

what is the quaternary structure of a protein

the combination of a number of different polypeptide chains and associated non protein groups into a large, complex protein molecule

what is important when it comes to how a protein functions

its 3D shape. it makes the protein distinctive and allows it to recognise and be recognised by other molecules. it can then interact with them in a specific way

hydrogen bonds

numerous but easily broken

ionic bonds in proteins

formed between any carboxyl and amino groups that are not involved in forming peptide bonds. they are weaker than disulfide bridges and easily broken by changes in pH

disulfide bridges

fairly strong, not easily broken

structure of cellulose

straight, unbranched chains that run parallel to each other allowing hydrogen bonds to form cross linkages between adjacent chains

how is the tertiary structure of a protein maintained

- disulfide bridges

- ionic bonds

- hydrogen bonds

tertiary structure of a protein

alpha helixes from the secondary protein structure can be twisted and folded even more to give a complex, specific, 3D structure of each protein

secondary structure of a protein

hydrogen bonds between the positively charged NH2 on one end of the chain and the negatively charged COOH group on the other end. these hydrogen bonds causes the polypeptide chain to be twisted into a 3D shaped such as the alpha helix

what does the primary structure of a protein determine

shape and therefore function

primary structure of proteins

polypeptide chains

in hydrogen bonding the individual bonds

are weak but can collectively form important forces that alter the physical properties of molecules

how are two AA linked

a new peptide bond between the carbon atom of one amino acid and the nitrogen atom of another

where does the water come from in a condensation reaction between 2 AA

the OH from the carboxyl group of one AA and the H from the amino group of another AA

2 AA monomers form a

dipeptide

AA R group

a variety of different chemical groups. each AA has a different R group. these 20 naturally occuring AA only differ in their R group

AA hydrogen atom

H

how are microfibrils formed in cellulose

the cellulose molecules are grouped together

AA carboxyl group

COOH. an acidic group. acid part of AA

AA amino group

NH2. a basic group from which the amino part of AA is derived from

what are the 4 chemicql groups that attach to the central carbon in AA

amino group, carboxyl group, hydrogen atom, R group

basic structure of AA

Central carbon atoms attached to 4 different chemical groups

what provides indirect evidence for evolution

the same 20 AA that naturally occur in proteins occur in all living organisms

monomers can be linked together to form

long chains called polymers

how many AA have been identified

100

how many AA naturally occur in proteins

20

what forms proteibs

polypeptides

what do lots of amino acid units combine to make

polypeptide

what are amino acids in terms of units

monomers

what type of molecules are enzymes

proteins

how are fibres formed in cellulose

microfibrils are arranged in parallel groups

why is a cloudy colour formed in an emulsion test if lipids are present

due to any lipid in the sample being finely dispersed in the water to form an emulsion. light passing through the emulsion is refracted as it passes from the oil drops to the water drops making it appear cloudy

test for lipids process

- take a completely dry and grease free test tube.

- add 2cm3 of sample and 5cm3 of ethanol.

- shake the tube thoroughly to dissolve any lipid in the sample.

- add 5cm3 of water and shake gently.

- a cloudly white colour indicates the presence of a lipid.

- as a control repeat the procedures using water instead of sample, the final solution should remain clear

covalent bonding

shared pair of electrons in outer shell

ionic bonding

ions with opposite charges attract

what is stronger covalent or ionic vonds

covalent

what is the process in which polymers are formed

polymerisation

hydrogen bonding

electrons within a molecule unevenly distributed, tend to spend more time at one position

what is the purpose of hydrogen bond Cross linkages in cellulose

although they are weak alone, collectively add strength

what do chains of mononucleotide sub units form

polynucleotides

what is the point of fibres and microfibrils

provide strength

what is formed when peptides that have amino acids as their basic sub unit are linked together

polypeptides

what does cellulose do

- major component of plant walls and provide rigidity to the plant cell.

- the cellulose cell wall prevents the cell from bursting as water enters it via osmosis by exerting an inward pressure that stops further influx of water which causes living plant cells to be turgid and push against one another, making non woody parts of the plant semi-rigid

in polymerisation in organisms each time a new sub unit is attached

a molecule of water is formed

why is it useful if parts of the plant are semi rigid (cellulose)

maintains stems and leaves in a turgid state so they can provide the max surface area for photosynthesis

condensation reaction

water produced

characteristics of lipids

- contain C, O, H.

- proportion of O to C and H is smaller in carbohydrates.

- insoluble in water.

- soluble in organic solvents (alcohols, acetone)

hydrolysis reaction

water used

what are the main groups of lipids

triglycerides and phospholipids

what is metabolism

all the chemical processes that take place in living organisms collectively

roles of lipids

- source of energy

- waterproofing

- insulation

- protection

- cell membranes

what is a molar solution

a solution that contains one mole of solute in each litre of solution

roles of lipids: cell membranes

phospholipids contribute to the flexibility of membranes and the transfer of lipid-soluble substances across them

carbon atoms unusual feature

they readily form bonds with other carbon atoms

roles of lipids: source of energy

when oxidised, lipids provide more than twice the energy of the same mass of carbohydrate and release valuable water

what does carbon readily forming bonds with other carbon atoms create

a backbone that other atoms can attach to

roles of lipids: waterproofing

lipids are insoluble in water and therefore used as a waterproofing. both plants and insects have waxy, lipid cuticles that conserve water, while mammals produce an oily secretion from the sebaceous glands in the skin

what are carbon containing molecules

organic molecules

roles of lipids: insulation

fats are slow conductors of heat and when stored beneath the body surface help to retain body heat. they also act as electrical insulators in the myelin sheath around nerve cells