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Biology > Proteins and enzymes > Flashcards

Proteins and enzymes Flashcards

1
Q

What are the roles of proteins?

A

Structural
Catalytic
Cell signalling
Immunological

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2
Q

What is the general structure of amino acids?

A

Contains an amine group, R group and a carboxylic acid group

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3
Q

What bonds hold together amino acids?

A

Peptide bonds

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4
Q

What molecule is produced from two amino acids

A

A dipeptide

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5
Q

What is a polypeptide

A

When more amino acids are added to a dipeptide a polypeptide is formed

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6
Q

What is the primary structure of proteins?

A

The order of amino acids, held together by peptide bonds.

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7
Q

What is the secondary structure of proteins?

A

Areas of initial folding
Held together by hydrogen bonds
Contains alpha helices and beta pleated sheets

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8
Q

What is the tertiary structure of proteins?

A

Interactions of the R groups.
The tertiary structure is the 3D shape
Maintained by 4 types of bond/interaction
- Hydrogen bonds
- Disulphide bridges
- Ionic Bonds
- Hydrophobic interactions

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9
Q

What is the quaternary structure

A

When two or more polypeptides join together
Or there is a prosthetic group
A conjugated protein is a globular protein with a prosthetic group

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10
Q

What are globular proteins

A

Usually have a spherical shape caused by tightly folded polypeptide chains
Hydrophobic groups on the inside and hydrophilic groups on the outside

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11
Q

Examples of globular proteins

A

Transport proteins - haemoglobin
Enzymes
Hormones - insulin

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12
Q

Describe the structure of haemoglobin

A

4 polypeptide chain subunits
- 2 alpha chains
- 2 beta chains
Each subunit contains a haem group containing Fe2+
Soluble

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13
Q

Describe the structure of amylase

A

Single chain of amino acids
Secondary structure has alpha helices and beta pleated sheets
Needs the cofactor Cl-
Soluble

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14
Q

Describe the structure of insulin

A

Two amino acid chains joined by disulphide bonds

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15
Q

What are fibrous proteins

A

Formed by parallel polypeptide chains held together by cross-links. these form long rope-like fibres
They have a high tensile strength and are generally soluble

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16
Q

What are three examples of fibrous proteins

A

Collagen
Keratin
Elastin

17
Q

Describe the role of collagen

A

Structural protein
Main component of connective tissue such as ligaments/tendons

18
Q

Describe the role of keratin

A

For protection
Main component of hard structures, including hairs/nails

19
Q

Describe the role of elastin

A

Elastic properties
Major component of tissues that require elasticity such as arteries/lungs

20
Q

What are three differences between Fibrous and globular proteins

A

Fibrous are insoluble where as globular are soluble

Fibrous proteins are elongated whilst globular are spherical

Fibrous proteins don’t contain a prosthetic group where as globular proteins do

21
Q

What is an enzyme

A

Globular proteins
Specific 3d tertiary structure
Soluble in water
Biological catalyst

22
Q

What is the lock and key theory

A

The active site is complimentary to the shape of the substrate
the substrate is the key and the active site is the lock

23
Q

What is the induced fit model

A

Once the substrate has bound the enzyme changes shape slightly to an even more exact fit
The enzyme then puts pressure on the bonds in the substrate so that it catalyses the reaction

24
Q

Give an example of an intracellular enzyme

A

Catalase

25
Q

Give an example of an extracellular enzyme

A

Amylase/Trypsin

26
Q

What is the activation energy

A

The minimum amount of energy required for a reaction to happen

27
Q

How does temperature affect the rate of an enzyme controlled reaction

A

Increasing temperature increases rate of reaction due to an increase in kinetic energy so there are more successful collisions between the enzyme and the substrate
Increasing temperature beyond the optimum reduces the rate has the bonds in the tertiary structure break causing the enzyme to become denatured

28
Q

How do vibrations affect the rate of an enzyme controlled reaction

A

More kinetic energy means more vibrations
which puts a strain on bonds in the tertiary
structure.
This can break the weaker bonds (H and
ionic) & change the shape of the active site.
As you heat an enzyme more & more bonds
are broken.
Rate of reaction decreases until tertiary
structure of enzyme unravels and denatures

29
Q

What is pH

A

Measure of H+ ion concentration.
The higher the H+ ions, the lower the pH value,
so acids contain a high concentration of H+ ions.

30
Q

How does pH effect the rate of an enzyme controlled reaction

A

Changing pH away from the optimum reduces the rate of reaction because the concentration of H+ ions affects the tertiary structure which can cause the enzyme to denature

31
Q

What is an inhibitor

A

Any substrate or molecule that slows down the rate of an enzyme controlled reaction

32
Q

What are the 4 types of inhibitors

A

Competitive inhibitors
Non-Competitive inhibitors
Permanent inhibitors
End product inhibition

33
Q

What are competitive inhibitors

A

Have a similar shape to the substrate
Occupy active site to form an enzyme-inhibitor complex
Substrate cannot fit into the active site
Tend to be reversible

34
Q

What are non-competitive inhibitors

A

Attach to an area away from active site (Allosteric)
Distorts the 3-D tertiary structure which changes the shape of the active site
substrate can no longer fit into active site
Tend to be permanent

35
Q

What is end product inhibition

A

To prevent build up of end product, the end product acts as a non-competitive inhibitor to slow down the reaction

36
Q

What are coenzymes

A

Small organic and non protein
temporarily bind to active site
take part in the reaction
Used again and again
Often vitamins

37
Q

What are cofactors

A

Inorganic ions
Can combine with the enzyme or substrate so that the enzyme substrate can be form easier

Biology (12 decks)

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