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AQA A-Level Biology 1-4 > 1.4.1 Proteins > Flashcards

1.4.1 Proteins Flashcards

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1
Q

What elements are in proteins?

A

Carbon
Hydrogen
Oxygen
Nitrogen

Sometimes - Sulfur and Phosphorus

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2
Q

What are the functions of proteins?

A 
Catalysts
Transporting substances around the body
Movement of the body 
Cell recognition 
Transport across cell surface membrane
Formation of connective tissue and structural components of the body
Protection against foreign bodies
Hormonal control
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3
Q

Example of catalyst protein?

A

Enzymes

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4
Q

Example of the proteins that transport substances around the body?

A

Haemoglobin

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5
Q

Example of the proteins that help movement of the body?

A

Actin and myosin in muscles

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6
Q

Example of the proteins for cell recognition?

A

Antigens

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7
Q

Example of the proteins that help transport across cell membrane?

A

Intrinsic protein channels

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8
Q

Example of the proteins that form connective tissue and structural components?

A

Keratin or collagen

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9
Q

Example of the proteins for protection against foreign bodies?

A

Antibodies

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10
Q

Example of the proteins for hormone control?

A

Insulin

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11
Q

What is the monomer for proteins?

A

Amino acids

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12
Q

What bonds are proteins held together by?

A

Peptide bonds

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13
Q

How many different occurring amino acid monomer units are there? How many essential ones?

A

20

Only 8 are essential to build the others

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14
Q

What are two amino acids joined together called?

A

Dipeptides

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15
Q

What are many amino acids joined together called? Process?

A

Polypeptides

Polymerisation

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16
Q

What is the structure of an amino acid?

A

An asymmetrical carbon atom bonded to 4 different groups

Carboxyl group - COOH
Amino group - NH2
One hydrogen atom
R - variable group

17
Q

What are optical isomers?

A

They are mirror image isomers

Eg Alpha amino acids and Beta amino acids

18
Q

What amino acids are all living things made from?

A

Alpha amino acid

19
Q

What word are amino acids described as? What does this mean?

A

Amphoteric

The amino acids can act as both acids and bases

20
Q

How can the amino acids act as both acids and bases?

A

The amino group (NH2) can accept a hydrogen becoming NH3+ (alkaline)

The carboxylic acid group can lose a hydrogen ion and become COO- (acid)

21
Q

What reaction is used to form a dipeptide?

A

Condensation reaction

22
Q

What is removed in a condensation reaction?

A

Water

23
Q

What are the two products in a condensation reaction of two amino acids?

A

Dipeptide and water

24
Q

What are the types of structures of proteins?

A

Primary
Secondary
Tertiary
Quaternary

25
Q

What is primary structure? Bonds involved?

A

The sequence of amino acids in the polypeptide chain which determines the shape and function - an unbranched polypeptide chain

Peptide bonds

26
Q

What is secondary structure? Bonds involved?

A

Polypeptide chains can twist into a 3D shape

Weak hydrogen bonds

27
Q

What are the two types of secondary structures?

A

Alpha helix

Beta pleated sheet

28
Q

How does an alpha helix structure work?

A

Weak hydrogen bonds between NH group of one amino acid and the CO group of the neighbouring amino acid to cause the coil

Making fibres

29
Q

What is alpha helix found in?

A

Keratin - hair and nails

Collagen - tendons

30
Q

How does the beta pleated sheet work?

A

Hydrogen bonds form parallel chains to produce a flat structure that then folds
Creates great strength

31
Q

What is beta pleated sheet found in?

A

Silk

32
Q

What are the two types of proteins?

A

Fibrous

Globular

33
Q

What is the structure and use of fibrous proteins?

A 
Made of long parallel fibres
Linked by cross-bridges (very stable)
Lots of molecules involved 
Regular and repetitive structure 
Insoluble

Used as structural molecules

34
Q

What is the structure and use of globular proteins?

A 
Rounded molecules 
Fewer molecules used
Unstable
Irregular structure 
Soluble

Often used for metabolic functions

35
Q

What is tertiary structure? Bonds involved?

A

A precise 3D structure of protein formed by coiling of secondary proteins

Hydrogen bonds (weak, easily broken)
Di-sulphide bridges (covalent bonds of sulphur atoms in the R group)
Ionic bonds (between amino or carboxyl groups that aren’t involved in peptide bonds) - weak and broken by changes in pH
36
Q

What is quaternary structure? Bonds involved?

A

Large proteins consisting of a number of individual polypeptide chains linked together in various ways
Also,
Non-protein groups can be joined to the polypeptide called a prosthetic group

Hydrogen
Ionic
Di-Sulphide bridges

37
Q

What do di-sulfide bridges do?

A

Joins or binds the polypeptide chains together

38
Q

How do you test for proteins?

A

Add equal volume of sodium hydroxide to the sample
Add Biuret reagent (copper sulphate solution)

If protein is present a purple/lilac colour will be indicted

AQA A-Level Biology 1-4 (20 decks)

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