Proteins 💘

Question 1

Proteins

Answer 1

A diverse group of large and complex polymer molecules

Made of long chains of amino acids

Question 2

Examples of roles of proteins

Answer 2

Structural:main components of the body tissues such as muscle skin ligaments and hair
Catalytic:all enzymes are proteins
Immunological:all antibodies are proteins

Question 3

Structure of proteins

Answer 3

All amino acids have this general structure
A central carbon atom and around this are these groups
One hydrogen atom above the carbon
Amino group:(NH2)
Carboxylic group :COOH (double bond between the c and o )
And an r group which has 20 different varieties as there are twenty amino acids

Question 4

1 structure of protein

Answer 4

The sequence of amino acids in its polypeptide chains

Question 5

2 structure of proteins

Answer 5

Interactions between amino acids cause the chain to form localised 3D sections
Two types:
Alpha helix and beta pleated sheet
Both maintained by hydrogen bonds

Question 6

3 structure of proteins

Answer 6

The overall 3D structure 
Several types of bonds hold the structure in place:
hydrophobic interactions
Ionic
Hydrogen bonds 
Disulfide bonds

Question 7

4 structure of proteins

Answer 7

proteins that have more than one polypeptide chain
Eg haemoglobin is made is made of four subunits
Has four iron containing haem groups which bind to oxygen
Fe2+
Two beta and two alpha subunits for haemoglobin

Question 8

Prosthetic groups

Answer 8

Conjugated proteins contain a non amino acid part called a prosthetic group
There to carry out a certain function

Question 9

Polypeptide

Answer 9

Many amino acids joined together by peptide bonds forming a polypeptide chain
Formed by a condensation reaction
The peptide bond forms between the carboxyl group on one amino acid and the amino group on the other amino acid

Question 10

Disulfide bonds

Answer 10

One of the most strongest and important bonds occurs between two cysteine amino acids

Question 11

Fibrous proteins

Answer 11

Formed by parallel polypeptides chains held together by cross links creating rope like fibres
Very strong
Insoluble in water
Eg keratin (main component of hard structures such as claws/nails)

Question 12

Globular proteins

Answer 12

Have a spherical shape cause by tightly folded polypeptide chains they’re folded so hydrophobic groups are on the inside and the hydrophilic are on the outside
This makes them soluble in water
Eg transport proteins such as haemoglobin

Question 13

Amino acid glycine

Answer 13

Basic amino acid structure with one hydrogen atom in place of the r group

Question 14

Test for proteins

Answer 14

Biuret test
Add few drops of biuret reagent to food sample
Blue copper sulfate and sodium hydroxide are added and is shaken
Turns purple in the presence of peptide bonds indicating that a protein is likely to be present
Colour is due to cu2+ ions having an attraction to adjacent pairs of co-nh groups in peptide bonds

Question 15

What is a non coding rna

Answer 15

Transcribed from dna but not translated

Question 16

Three major classes of ncrna

Answer 16

Micrornas involved in RNA induced silencing useful against viral infections
Piwi interacting rnas pirna rna silencing via formation of risc (rna induced silencing complex)
Short interfering rna sirna small double stranded rna which binds with risc risc breaks double strand into separate strands w one attached to risc can gene silence by binding to complementary mrna and slicing it known as rna interference rnai

Question 17

What’s a transcription factor

Answer 17

A protein which binds to a specific DNA sequence and controlled the rate of transcription
Promote or block recruitment of rna polymerase

Question 18

Promoter

Answer 18

Promoter is a site in dna in which rna polymerase binds to and initiates transcription of dna to rna

Question 19

Sense strand vs antisense

Answer 19

Sense is coding strand of dna whereas antisense is complimentary to sense strand and is used as the template by rna polymerase during transcription

Question 20

Translation

Answer 20

Initiated at start codon aug
tRNA has anti codons which binds to the codons and an amino acid
Works from 5’ to 3’
Ribosome catalysed addiction of new amino acids to peptide chain
Stop codon results in translation to stop via the ribosome to break down

Question 21

Which molecule contains the genetic code

Answer 21

Mrna

Question 22

Transcription occurs along a ___ template forming mRNA in ____ direction

Answer 22

3’ to 5’ then 5’ to 3’