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AS Biology > Protein > Flashcards

Protein Flashcards

1
Q

Elemental composition of proteins

A

Carbon, Hydrogen, Oxygen, Nitrogen, some sulphur

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2
Q

Protein structure generally

A

Amino group, variable group, carboxyl group

20 different amino acids, vary by R group

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3
Q

Protein behaviour in water

A

Amino acids dissolve in water, carboxyl dissociates freeing a hydrogen atom, -ve charged
Amino acid acquires H+
Amino acid has +ve and -ve charge, zwitterion

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4
Q

Dipeptide formation

A

Condensation reaction form dipeptide and water

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5
Q

Primary structure

A

Sequence of amino acids in polypeptide chain
Created by condensation reactions between many amino acids
Due to variation in chemical makeup of R group, interactions between amino acids in chain

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6
Q

Secondary structure

A

Amino acid chain folds into alpha helix or beta pleated sheets
Due to hydrogen bonds between amino (+ve) and carboxyl group (-ve)

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7
Q

Tertiary structure

A

Secondary structure folds even more
Unique 3D structure formed
Held together by disulphides bonds, ionic bonds, hydrogen bonds
Not all proteins fold into tertiary shape

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8
Q

Strength of disulphide bonds

A

Fairly strong

Not easily broken

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9
Q

Strength of ionic bonds

A

Weaker than disulphide bonds and easily broken by pH changes

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10
Q

Strength of hydrogen bonds

A

Weakest bond

But numerous

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11
Q

Quaternary structure

A

Large proteins formed from no of polypeptide chains

Can include prosthetic groups

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12
Q

Types of proteins

A

Fibrous

Globular

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13
Q

Fibrous protein properties

A 
Structural
Large insoluble, strong, flexible
Form long parallel chains like cellulose
2ndary level of folding
Often have repeating amino acid sequences
Do not denature as easily as globular
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14
Q

Examples of fibrous proteins

A

Collagen- in tendons, cartilage
Keratin- in nails, skin, horns, claws
Elastin- ligaments
Actin, Myosin- muscle fibres

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15
Q

Globular proteins properties

A

Tertiary structure, resembles globule, compact shape
Often involved in controlling, cellular metabolism
Specific shape
Water soluble, colloidal solutions
Altered easily, not stable, denature more easily

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16
Q

Examples of fibrous proteins

A

Enzymes
Carriers and receptors in membranes
Antibodies
Haemoglobin

17
Q

Chemical reactions

A

When reactants collide, enter transition state
Molecule become strained, molecules activated
In transition state, more chance of strained bonds breaking, new bonds forming
Under normal conditions, very few have enough KE to enter transition state

18
Q

Catalysts, activation energy

A

Catalyst provides lower energy pathway

Reacts more rapidly, bind to catalyst, speed up biological reactions

19
Q

Structure of enzymes

A

Globular
Specific 3D shape, result of amino acid sequence, R groups
Small region involved in catalysing reactions, active site
Active site made up of small no of amino acids
No change to nature of products, energy change during reaction, catalyst

20
Q

Lock and key theory

A

Specific shaped substrate fits in specific complementary
Enzyme substrate complex formed
Products formed, no change to enzyme shape

21
Q

Advantages and disadvantages of the lock and key theory

A

Explains enzyme specificity

Assumes enzyme is rigid
Not supported by observation that molecules bind to allosteric site that can alter active site shape

22
Q

Induced fit model

A

As substrate approaches enzyme, shape changes
Reaction proceeds as enzyme, substrate binds
Products released, enzyme returns to original shape
Causes conformational change in enzyme

23
Q

Advantages of the induced fit theory

A

Explains how other molecules affect enzyme activity

Explains how activation energy is lowered

24
Q

Effect of temperature on enzyme activity at optimum

A

High temperature, high KE of molecules
Greater no of successful collisions, producing enzyme substrate complexes
Greater rate of reaction

25
Q

Effect of temperature beyond optimum

A

Increased temperature cause atoms within molecule to vibrate more energetically
Increased vibrations strain bonds, bonds break, active site changes shape

26
Q

Effect of pH on enzyme activity

A

Change in pH alters charges on amino acids make up active site, enzyme substrate complex cannot be formed
Changes tertiary structure
Denatures enzyme

27
Q

Effect of substrate concentration on enzyme activity

A

Activity of enzyme depends on no of substrate molecules/sec, bind to form enzyme substrate complexes
More substrate molecules=more successful collisions, more enzyme substrate formed, more product

28
Q

Coenzymes

A

Small organic non protein molecules, carry chemical groups between enzymes
Consumed in reactions in which they are substrates
Regenerated, con maintained in the cell

29
Q

Prosthetic group

A

Special subset of coenzymes, non protein parts of conjugated proteins
Involved in active site of enzymes

30
Q

Control of metabolic pathways

A

Series of reactions, each step catalysed by enzymes
Highly structured
Non competitive
Level of any chemical maintained at constant level with end product inhibition

31
Q

Enzyme inhibitors

A

Directly, indirectly interferes with AS function
Reversible, irreversible
Competitive, non competitive

32
Q

Competitive

A

Complementary to AS shape
Bind to AS, prevent substrate binding
Temporary, quickly released

33
Q

Effect of competitive inhibitors on rates of reaction

A

Increase substrate concentration, more substrate binds to AS in preference to inhibitor

34
Q

Non competitive inhibitors

A

Attach to allosteric site
Produce conformational change in enzyme molecule including AS
Substrate will not fit completely

35
Q

Effect of non competitive inhibitors on rate of reaction

A

Increasing substrate no will not affect rate of reaction

AS Biology (29 decks)

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