Unit 2 - Module 1 - Proteins

Question 0

What percentage do proteins make up the organic matter of a cell?

Answer 0

50%

Question 1

What are the functions of proteins?

Answer 1

Structural components
Membrane carriers and pores
All enzymes are proteins
Many hormones 
Antibodies

Question 2

What are proteins made from?

Answer 2

Made by joint amino acids together.

Question 3

What is the basic structure of an amino acid?

Answer 3

An amino group at one end
An acid group at the other end
A carbon in the middle bonded to a H and R- group.

Question 4

How many types of amino acids are there?

Answer 4

20

Question 5

What is the simplest amino acid? And what is the R-group?

Answer 5

Glycine

H

Question 6

How do plants obtain amino acids?

Answer 6

They can manufacture them, as longer as the can obtain nitrate for the soil. This is then converted to amino groups and bonded to organic groups made from products of photosynthesis.

Question 7

How do animals obtain amino acids?

Answer 7

They must take in proteins as part of their diet. These are digested to amino acids.

Question 8

What are essential amino acids?

Answer 8

They are an essential part of the diet. Some amino acids (8-10) cannot be built from materials taken in by animals bodies.

Question 9

How can vegetarians get the essential amino acids?

Answer 9

Soya contains all of them.

Question 10

What is the name of the bond that forms between two amino acids?

Answer 10

Peptide bond.

Question 11

What is it called when two amino acids are joined together?

Answer 11

It is a dipeptide.

Question 12

How are polypeptides and proteins made?

Answer 12

They are synthesised in cells on ribosomes. Protein synthesis.
Uses information in the form of mRNA.

Question 13

What is the primary structure of a protein?

Answer 13

It is given by the specific sequence of amino acids that make up the protein.

Question 14

What enzymes break down peptide bonds?

Answer 14

Protease enzymes.

Question 15

What are two examples of proteins being broken down?

Answer 15

Hormone regulation

Ageing

Question 16

Why are enzymes important in hormone regulation?

Answer 16

It is vital that hormones are broken down so effects aren’t permanent and can be controlled. Any cell targeted by hormone contains enzymes that can break it down.

Question 17

Why are enzymes important in ageing?

Answer 17

One feature of ageing is that skin loses elasticity and becomes wrinkled. This is because older skin is less able to rebuild collagen and other proteins.

Question 18

What are the forms of secondary structure?

Answer 18

Alpha helix

Beta-pleated sheet.

Question 19

What hold the coils in place?

Answer 19

Many hydrogen bonds form giving great stability to parts of the protein molecule.

Question 20

What is the tertiary structure?

Answer 20

It the overall 3-D shape of the protein, formed when the coils and pleated themselves coil or fold.

Question 21

How is the tertiary structure held in place?

Answer 21

Disulphide bonds
Ionic bonds
Hydrogen bonds
Hydrophobic and hydrophilic interactions.

Question 22

How do disulphide bonds form?

Answer 22

The amino acid cysteine contains sulphur. When two are close together a covalent bond can form.

Question 23

How do hydrophobic and hydrophilic interactions maintain the tertiary structure?

Answer 23

In a water based environment hydrophobic amino acids will be most stable if they are held together with water excluded. Hydrophilic amino acids tend to be found on the outside of globular proteins, with hydrophobic ones in the centre.

Question 24

What is the effect of heating a protein?

Answer 24

It increases the kinetic energy. Causes whole molecules to vibrate and breaks some bonds holding tertiary structure.
If enough heat tertiary structure can unravel and protein no longer function.

Question 25

Describe globular proteins.

Answer 25

Roll up to form balls.
Usually soluble in water
Usually have metabolic roles.
E.g. Enzymes, plasma proteins, antibodies.

Question 26

Describe fibrous proteins.

Answer 26

Form fibres.
Usually insoluble in water.
Usually have structural role.
E.g. Collagen, keratin,

Question 27

What is the quaternary structure?

Answer 27

Som proteins are mad from more than one polypeptide subunit and inorganic components.

Question 28

What is the quaternary structure of haemoglobin?

Answer 28

Four polypeptide subunits.
Two are alpha chains
Two are beta chains
Haem group with Fe2+ ion.

Question 29

What are prosthetic groups?

Answer 29

A non-protein organic molecule that forms a permanent part of a functioning protein molecule.

Question 30

A summary of haemoglobin.

Answer 30

Globular protein
Soluble in water
Wide range of amino acid constituents in primary structure.
Contains prosthetic group - haem group.
Much is wound into alpha helix structures.

Question 31

What forms a collagen molecule?

Answer 31

Three polypeptide chains wound around each other.
Each chain is itself a coil of around 1000 amino acids.
Hydrogen bonds between chains.

Question 32

What gives collagen it’s strength?

Answer 32

Each collagen molecule forms covalent bonds with other molecules.
These cross links are staggered along molecules.
Results in collagen fibril.
Many fibrils form a collagen fibre.

Question 33

Where does collagen provide mechanical strength?

Answer 33

In walls of arteries, prevents blood at high pressure from bursting walls.
Tendons connect skeletal muscles in bones. Mostly collagen.
Bones formed from collagen, reinforced with calcium phosphate.
Cartilage and connective tissue made from collagen.

Question 34

How is collagen used commercially ?

Answer 34

Cosmetic treatments. Injected into lips to give a fuller appearance.

Question 35

What does a collagen molecules mostly consist of?

Answer 35

35% of primary structure is glycine.

Left handed helix structures.