2.4 Proteins

Question 1

How am a are assembled into proteins

Answer 1

Am a linked by peptide bonds in condensation reactions (H2O forms) to form polypeptides - in translation

Amino and carboxyl ends - terminals

Question 2

Define: dipeptide, polypeptide, oligopeptide

Answer 2

Dipeptide: a molecule consisting of two ami a linked by peptide bond

Polypeptide: a molecule consisting of many am a linked by peptide bonds

Oligopeptide: chains of polypeptides of fewer than 20 am a linked by peptide bonds

Question 4

Diversity of am a

Answer 4

Different R groups lead to diversity of am a -> 20 different -> if x am a in polypep - 20^x variations

Diverse properties of am a:

• hydrophilic/hydropohobic
• polarity/non-polarity
• rings
• charged/non-charged
• basic/acidic

Question 5

Am a and origins of life

Answer 5

1. Not all organisms share the same am a
2. Am a were produced by chemical processes before origin of life - some organisms used
3. Ideal 20 am a for making wide range of proteins - natural selection favoured organisms which used am a
4. All life evolved from single ancestor which used all 20 am a - polyppetides are made by ribosomes in all species

Question 6

How genes and polypeptides are linked

Answer 6

1. Am a sequence of a polypeptide is coded by a gene
2. Genes store instructions fro making the sequence
3. Three bases code for one am a - but genes always longer, so if 20 am a in sequence - 20x3+x = >60 bases
4. Gene transcribed into mRNA - to ribosomes
5. mRNA translated to am a sequence by tRNA and anticodons

Question 7

Importance fo protein conformation

Answer 7

Conformation determines function of protein

Question 8

Shapes of proteins

Answer 8

Question 9

Protein structures

Answer 9

1. Primary (ribosomes): only sequence, non-functional
2. Secondary (cytoplasm): alpha helices and beta pleated sheets (H bonds), functional
3. Tertiary (Golgi, rER): bonds bwteen adjacent chains (H bonds, dipole, disulfide bridges, ionic), become globular - 3D
4. Quaternary (Golgi): many polypeptides come together

Question 10

Denaturation of proteins

Answer 10

Denaturation: loss of 3D conformation, bonds between R broken

1. pH: reversible, charges of R hroups changed, soluble proteins can become insoluble
2. Temperature: irreversible, vibrations - bond breaking, proteins differ in heat tolerance

Question 11

Protein functions in organisms

Answer 11

Question 12

Industrial uses of proteins

Answer 12

1. Detergents: removing stains
2. Monoclonal antibodies: pregnancy tets, HIV test, COVID test
3. Treatment: insulin, vaccines
4. Lactose catalysis - lactose intolerence

Question 13

Rubisco

Answer 13

• enzyme in plant leaves
• fixes CO2 form atmosphere - plant photosynthesis
• most abundant protein on Earth

Question 14

Insulin

Answer 14

• hormone
• receptors for insulin - bind reversibly
• signals cells to absorb glucose from blood
• diabetes I - insufficinet production
• diabetes II - disruption of receptors

Question 15

Immunoglobulins

Answer 15

• antibodies
• bind to antigens - immune response - phagocytosis of pathogen

Question 16

Rhodopsin

Answer 16

• pigment
• absorbs light in rod cell membranes in retina
• absorbs light - changes shape - nerve impulse

Question 17

Collagen

Answer 17

• fibrous protein
• gives strength, prevents from tearing
• in skin, blood vessels, teeth, bones

Question 18

Spider silk

Answer 18

• proetins produced by spiders
• parallel arrays formed from polpeptides
• very strong - stretchy

Question 19

Define proteome:

Answer 19

PROTEOME: the totlaity of proteins produced by a cell, tissue or ogranism

Every individual has a unique proteome

Proteomes vary in different cells in organism - unlike genome

Question 20

Research techniques in proteins

Answer 20

1. Gel electrophoresis - separation + identification
2. Fluorescant antibody tagging - identify transport + if protein is present