Unit 2 - Proteins

Question 1

What are the monomeric units of proteins?

Answer 1

Amino acids

Question 2

Where do we get amino acids from?

Answer 2

Our diet

Question 3

Outline the journey an amino acid takes from food to protein in a cell

Answer 3

• food is ingested
• enzymes in the stomach/small intestine hydrolyse protein into amino acids
• the amino acids are absorbed by the gut wall into the blood
• the amino acids leave the blood in the tissue fluid and enter cells
• proteins are synthesised on the ribosomes

Question 4

How many common amino acids are there?

Answer 4

20

Question 5

Give 4 functions of proteins

Answer 5

• enzymes
• hormones
• antibodies
• structural proteins

Question 6

What do the interactions of differing R-groups determine?

Answer 6

The folding of the protein

Question 7

What type of reaction occurs to form a protein from 2 amino acids?

Answer 7

Condensation

Question 8

What type of bond is formed from the synthesis of a protein?

Answer 8

Peptide

Question 9

What is produced in the condensation reaction between two amino acids?

Answer 9

Water and dipeptide

Question 10

What is the general formula of an amino acid?

Answer 10

Question 11

Between which parts of the amino acid molecules does the condensation reaction between two amino acids occur?

Answer 11

The carboxyl group of one amino acid and the amine group of another amino acid

Question 12

What is a chain of amino acids called?

Answer 12

A polypeptide

Question 13

What is the end of a polypeptide with an amino group called?

Answer 13

The N-terminus

Question 14

What is the end of the polypeptide with a carboxyl group called?

Answer 14

The C-terminus

Question 15

What is the definition of primary structure of a protein?

Answer 15

The SEQUENCE of amino acids

Question 16

What type of bonding holds the primary structure of a protein together?

Answer 16

Peptide

Question 17

What shape is the primary structure of a protein?

Answer 17

Linear

Question 18

What forms the secondary structure of a protein?

Answer 18

The folding of the primary structure

Question 19

What type of bonds hold together the secondary structure of a protein?

Answer 19

Hydrogen bonds

Question 20

In the secondary structure, what do hydrogen bonds form between?

Answer 20

Partially positive H and partially negative O

Question 21

What are the two possible shapes of the secondary structure?

Answer 21

• alpha helix
• beta pleated sheet

Question 22

What is the tertiary structure formed by?

Answer 22

The folding of the secondary structure

Question 23

Why do proteins fold at the tertiary level of structure?

Answer 23

Due to the interactions between the R-groups

Question 24

What are the 4 types of bond formed at the tertiary level of structure?

Answer 24

• ionic bonds
• hydrogen bonds
• disulfide bonds
• hydrophobic and hydrophilic interactions

Question 25

What do ionic bonds form between?

Answer 25

Positively and negatively charged ions

Question 26

What do hydrogen bonds form between?

Answer 26

Partially positive H and partially negative O

Question 27

What do disulfide bridges form between?

Answer 27

Sulfur atoms contained within R-groups

Question 28

Which amino acid contains sulfur?

Answer 28

Cysteine

Question 29

What do hydrophobic and hydrophilic interactions form between?

Answer 29

Polar and non-polar R-groups

Question 30

What kind of shape does the tertiary structure have?

Answer 30

3D

Question 31

What forms the quaternary structure?

Answer 31

Formed by the interaction of more than one tertiary protein and/or with prosthetic groups

Question 32

What type of bonds holds together the quaternary structure?

Answer 32

-ionic -hydrogen -disulfide -hydrophobic and hydrophilic interactions

Question 33

What is a prosthetic group?

Answer 33

a permanently bound non-protein component of a conjugated protein

Question 34

Define simple proteins

Answer 34

Proteins without a prosthetic group

Question 35

Give 3 characteristics of globular proteins

Answer 35

-compact -water soluble -roughly spherical

Question 36

Why are globular proteins water soluble?

Answer 36

-TERTIARY structures are folded so that the hydrophobic R-groups are kept away from the aqueous environment -hydrophilic R-groups are on the outside

Question 37

What are globular proteins used for?

Answer 37

-regulating many processes (enzymes)

Question 38

Give examples of the processes globular proteins regulate

Answer 38

-muscle contraction -immunity -chemical processes

Question 39

Give an example of a globular protein

Answer 39

Insulin

Question 40

Why is it beneficial for insulin to be water-soluble?

Answer 40

-insulin is a hormone -hormones are transported in the blood so must be water soluble

Question 41

What is the function of insulin?

Answer 41

Regulates blood glucose

Question 42

Are conjugated proteins a type of globular protein?

Answer 42

Yes

Question 43

What do conjugated proteins contain?

Answer 43

A non-protein prosthetic group

Question 44

Give an example of 2 conjugated proteins

Answer 44

Haemoglobin and Catalase

Question 45

What is the function of haemoglobin?

Answer 45

Carries oxygen in the blood in erythrocytes

Question 46

What is haemoglobin made up of?

Answer 46

2 alpha-helices 2 beta-pleated sheets

Question 47

How many subunits make up haemoglobin?

Answer 47

4

Question 48

What does each haem group contain?

Answer 48

Iron 2+ ion

Question 49

What does each subunit of haemoglobin contain?

Answer 49

A haem group

Question 50

How do haem groups allow erythrocytes to carry out their function?

Answer 50

Iron ions in haem groups can reversibly combine with an oxygen molecule

Question 51

How many oxygen atoms can one haemoglobin molecule carry?

Answer 51

8- remember ATOMS not MOLECULES

Question 52

Define globular protein

Answer 52

spherical, water-soluble proteins

Question 53

Define fibrous protein

Answer 53

long, insoluble, structural proteins

Question 54

What is the function of catalase?

Answer 54

Break down of hydrogen peroxide which otherwise is harmful to cells

Question 55

What type of protein is catalase?

Answer 55

Conjugated

Question 56

What type of prosthetic group does catalase contain?

Answer 56

Haem

Question 57

How many haem groups does catalase contain?

Answer 57

4

Question 58

Give 3 examples of fibrous proteins

Answer 58

Collagen Elastin Keratin

Question 59

Where is Keratin found?

Answer 59

In hair, skin, and nails

Question 60

How does the primary structure of repetitive amino acid sequences affect the properties of fibrous proteins?

Answer 60

-gives them organised structures -makes strong molecules that do not fold into complex 3D shapes

Question 61

Which amino acid does keratin contain in a high proportion?

Answer 61

Cysteine

Question 62

What does Cysteine contain in its R-group?

Answer 62

Sulfur

Question 63

What type of bonding occurs a lot in keratin?

Answer 63

Disulfide bonds

Question 64

How does a high proportion of disulfide affect the properties of keratin?

Answer 64

It makes it inflexible and strong

Question 65

Where is elastin found?

Answer 65

In the walls of blood vessels and alveoli of lungs

Question 66

What does elastin allow tissues to do?

Answer 66

Expand and return to size

Question 67

Why is it beneficial for tissues to contain elastin?

Answer 67

It confers strength and elasticity

Question 69

Where is collagen found?

Answer 69

In the skin, tendons, ligaments, and nervous system

Question 70

Why does collagen contain glycine for every 3rd amino acid?

Answer 70

Glycine is the smallest amino acid and so they can pack together more tightly

Question 71

What property does collagen have?

Answer 71

Flexibility

Question 72

Define polypeptide

Answer 72

Chains of 3 or more amino acids

Question 73

Define protein

Answer 73

one or more polypeptides arranged as a complex macromolecule

Question 74

what are essential amno acids? how many

Answer 74

amino acids we can only get form our diet. 9

Question 75

what are non-essential amno acids? how many

Answer 75

amino acids are body can make. 5