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Biology > Proteins > Flashcards

Proteins Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is a protein?

A

A macromolecule consisting of the elements carbon, hydrogen, oxygen and nitrogen, made of one or more polypeptide chains.

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2
Q

If the monomer is an amino acid, what is the polymer?

A

A peptide

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3
Q

Which groups are constant in an amino acid and which change to determine what amino acid it is?

A

Constant - amine, carboxyl, hydrogen

Change - R group

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4
Q

How many amino acids found in cells?

A

20

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5
Q

How many nonessential amino acids? Why are they non essential?

A

5, can be synthesised from other amino acids

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6
Q

How many essential amino acids? Why are they essential?

A

9, can only be found in our diet

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7
Q

How many ‘conditionally’ essential? Why are they thus?

A

6, only needed in infants and growling children

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8
Q

What are the terminals in an amino acid?

A

N terminal- amine group

C terminal- carboxyl group

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9
Q

What can an amino acid do in terms of hydrogens (protons)? WHAT IS THIS CALLED?

A

it can lose hydrogens from the CARBOXYL group, it can ‘mop up’ hydrogens from the AMINE group - AMPHOTERIC

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10
Q

Which groups in amino acids react to form peptides? What do they each give?

A

The amine group and carboxyl group.
The amine group gives H
The carboxyl group gives OH

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11
Q

What is the bond formed between two amino acids?

A

Peptide bond
O H
|| |
C—N

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12
Q

What is formed when two amino acids react?

A

A dipeptide

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13
Q

What is formed when more than 2 amino acids join?

A

A polypeptide.

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14
Q

What are the levels of protein synthesis?

A

Primary, Secondary, Tertiary, Quaternary

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15
Q

What is the primary structure?

A

The SEQUENCE of amino acids in the polypeptide chain.

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16
Q

What importance does the primary structure have?

A

It influences the shape the proteins fold into, and so influences the protein’s function.
Influences WHERE the hydrogen bonds form

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17
Q

What is the secondary structure?

A

The secondary structure is the result of formation of hydrogen bonds between different amino acids in the same chain

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17
Q

Where are the hydrogen bonds in an alpha helix

A

Between every first and fourth amino acid in the same polypeptide chain

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18
Q

Where are the hydrogen bonds in beta pleated sheet?

A

Between layers of the same polypeptide chain

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19
Q

How do hydrogen bonds formed between amino acids?

A

Between the double bonded oxygen and the hydrogen between R groups

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20
Q

What is the tertiary structure of a protein?

A

This is the interaction of Rgroups between different amino acids in the same polypeptide chain to determine the proteins shape when it folds

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21
Q

Name the different types of R group interactions in the tertiary structure, form weakest to strongest

A

Van der Waals (hydrophobic/hydrophilic)
Hydrogen
Ionic
Disulfide bridges (covalent)

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22
Q

How do you disulphide bridge bonds arise?

A

When the protein contains cysteine , which contains sulfur.

23
Q

What determines whether the amino acid chain forms an alpha helix or beta pleated sheet?

A

The load/sequence of amino acids in the chain.

24
Q

What does high-temperature do to proteins?

A

High temperature will break the Van der Waals - hydrophobic/hydrophilic - attractions in the tertiary structure and the protein will unravel and lose its shape and will not be able to perform its function anymore

25
Q

What is quaternary structure of a protein?

A

This is the interactions between different polypeptide chains

26
Q

What is quaternary protein?

A

A protein consisting of more than one polypeptide chain

27
Q

What are the quaternary proteins we are supposed to know?

A

Catalase, haemoglobin, insulin, collagen, keratin, elastin

28
Q

What is a globular protein?

A

Soluble proteins with a roughly spherical shape

29
Q

Name the globular proteins we need to know

A

Haemoglobin catalase insulin

30
Q

Why are globular proteins spherical in shape?

A

Due to the tertiary structure. The hydrophobic amino acids abounded towards the interior whereas the hydrophilic amino acids are towards the exterior and there is an equal proportion of hydrophobic and hydrophilic amino acid that the protein had a globular shape.

31
Q

Why are globular proteins soluble?

A

The hydrophilic amino acids face outwards and can interact with the water molecules

32
Q

What is the structure of haemoglobin

A
  • 4 polypeptide chains, 2 alpha globin 2 beta globin
  • Each polypeptide chain has a haem group associated with it
  • the haem group is a prosthetic group which contains iron
33
Q

What is a conjugated protein and give examples?

A

A conjugated protein is a protein with a prosthetic group which is a non-protein component
Haemoglobin Catalase

34
Q

What is the role of iron in haemoglobin and why is this useful?

A

Iron allows haemoglobin to bind with oxygen reversibly which is useful because the blood may need to be oxidised or reduced depending on its pH

35
Q

Describe the function of haemoglobin

A

Haemoglobin transports oxygen around the blood

36
Q

What is the structure of catalase?

A

Catalase is a tetramer which means it has four polypeptide chains

  • 4 haem groups
  • Very similar to haemoglobin except the haem groups are not attached to the polypeptide chains
37
Q

What is the function of catalase?

A

Catalase breaks down hydrogen peroxide which is a natural waste product in the human body and is poisonous

38
Q

What does the iron do in catalase?

A

It catalyses the breakdown of hydrogen peroxide

39
Q

Why is catalase being an antioxidant important?

A

It breaks down hydrogen peroxide into water and oxygen and this is important because oxidation leads to free radicals which produces chain reactions which are dangerous

40
Q

Describe what insulin is (cell)

A

Insulin is a peptide hormone
it cannot diffuse through the phospholipid bilayer so must attach to a receptor with a complimentary shape outside the cell so it can enter

41
Q

Describe the structure of insulin

A

2 polypeptide chains one starts with alpha helix and one ends with a beta pleated sheet
- disulfide bonds between chains due to cysteine

42
Q

What is a fibrous protein?

A

It is a long and insoluble protein

43
Q

Why are fibrous proteins long

A

They are made up of a repetitive, limited range of amino acids

44
Q

Why are fibrous proteins insoluble?

A

They have a higher proportion of hydrophobic R groups then hydrophilic R groups so cannot fully arrange themselves so that the hydrophobic R groups are in the interior of the protein
CANNOT INTERACT W WAER

45
Q

Where is collegan and found?

A

Skin tendons Cartilage

46
Q

What is the structure of collagen

A

2 polypeptide chains wrapped around each other in a helix
Hydrogen bonding between the chains stabilises and strengthens the structure
Cross linking covalent between collagen molecules stabilises

47
Q

What is the structure of keratin

A

2 polypeptide chains with lots of cysteine and so lots of disulphide bridges
lots of covalent bonds
so very strong and rigid
inflexible

48
Q

Where is keratin found

A

Hair skin nails

49
Q

What does keratin do in the -skin and what is it doing the -nails and hair

A

Skin- gives epithelial cells strength

Hair and nails- gives strength and inflexibility

50
Q

What does keratin do to compensate for a lack of sulphur

A

It makes saline and hydrogen bonds to connect the polypeptide chains

51
Q

Where is elastin found

A

Blood vessels, alveoli, arteries

52
Q

What does elastin do

A

It expands and contracts and allows the structure to return back to its original length/shape

53
Q

What is the structure of elastin

A

Many monomers calld tropoelastin connected together via interactions between the hydrophobic areas which is stabilised by cross links (covalent bonds) between lysine rich areas

54
Q

What does elastin do in arteries

A

When blood passes through with lots of pressure all the elastin expands and when the blood goes back the artery contracts again

55
Q

which amino acids dont end with an -ine and why

A

if they have an acidic R group

56
Q

describe the peptide bond

A
  • due to electron arrangement, acts as a double bond

- stiff and limited rotation

Biology (25 decks)

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