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Core Principles Eduqas Biology A Level > Proteins > Flashcards

Proteins Flashcards

1
Q

What is a monomer of protein called?

A

Amino acid

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2
Q

What is a dimer of a protein called?

A

Dipeptide

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3
Q

What is a a polymer of a protein called?

A

Polypeptide. This is a functional protein

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4
Q

What is an amino acid? And what is its structure?

A

It is the monomer of any protein molecule. It has a central carbon atom. To the right of it there is a carboxylic acid group (COOH) and to the left is an amino /amine group (NH2). Above we draw a hydrogen atom and below we put the letter r which stands for a functional group. There are 20 different functional groups and these determine what amino acid it is. Glycine would have a hydrogen atom. Cysteine would have CH2SH, which is the only functional group with Sulphur in.

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5
Q

What elements do proteins mostly contain?

A

Nitrogen, carbon , hydrogen, oxygen

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6
Q

What is the name for a bond between two amino acids

A

Peptide Bond

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7
Q

What does a peptide Bond look like structurally?

A

A bubble is drawn around the remaining oxygen and carbon atom of the carboxylic acid and the hydrogen and nitrogen from the the amino group.

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8
Q

Where does the water molecule come from in a condensation reaction between two amino acids?

A

It is the oh of the carboxylic acid group and and the bottom H of the amino group.

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9
Q

What are the two types of functional proteins AKA polypeptides?

A

Metabolic / globula and structural / fibrous

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10
Q

Give an example of metabolic globular polypeptide

A

Enzymes, haemoglobin, antibodies, hormones

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11
Q

Give examples of structural / fibrous polypeptides

A

Collagen, keratin, myosin and actin

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12
Q

What does it mean for a protein to be metabolic / globular?

A

They have metabolic roles so involved in chemical reactions and are compact. ‘Metabolic’ describes the function, globular the shape.

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13
Q

What does it mean for a proteins to be structural / fibrous?

A

It means they have structural roles for example in hair and are extended rather than compact. Structural describes the function, globular the shape.

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14
Q

What levels of protein structure do metabolic / globular polypeptides have?

A

Tertiary or quaternary

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15
Q

What levels of protein structure do structural / fibrous polypeptides have?

A

Secondary or quaternary

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16
Q

Give an example of a tertiary metabolic / globular polypeptide

A

Enzymes

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17
Q

Give two examples of quaternary metabolic / globular polypeptides

A

Haemoglobin and antibodies

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18
Q

Give an example of quarternary / fibrous polypeptide

A

Collagen

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19
Q

What are the four levels of protein structure?

A

Primary sequence, secondary structure, tertiary structure, quaternary structure

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20
Q

How many polypeptides are in a gene?

A

1

21
Q

How many peptide bonds are there in comparison to number of amino acids?

A

There is always one less peptide Bonds than there are amino acids

22
Q

Describe a primary sequence of amino acids

A

The primary sequence is non-functional and is simply a sequence of amino acids held together by peptide bonds.

23
Q

What are the two types of secondary structure proteins?

A

Alpha helix and beta pleated sheet

24
Q

Describe the alpha helix secondary structure of proteins

A

Hydrogen bonds form between between amino acids at different locations in the polypeptide chain. These bonds between oxygen and hydrogen atoms cause the polypeptide chain to coil into a helix.

25
Q

Describe a beta pleated sheet secondary structure of proteins

A

Hydrogen bonds form between hydrogen and oxygen atoms again but this time it is between two parallel adjacent chains rather than the same chain on top of itself. This means he pleated sheet forms instead.

26
Q

Can polypeptides chains exist as both alpha helix and beta pleated sheets?

A

Yes. If it is a massive polypeptide chain, the polypeptide chain can be a combination of the two.

27
Q

Describe the basics of a tertiary structure polypeptide

A

Tertiary structured polypeptides are formed when secondary structure proteins , keeping the hydrogen bonds, develop further into tertiary structure protein. They are the irregular folding of a polypeptide chain into a globular shape.

28
Q

Describe all the the additional Bonds in in a tertiary structure protein

A

More hydrogen bonds. These form in the R groups between oxygen and hydrogen atoms. Ionic bonds form between positively and negatively charged R groups e.g. NH3+ and O-. Disulfide Bridges form between pairs of cysteine amino acids. The two functional groups bond between their sulphur atoms so it’s backbone-CH2-S-S-CH2-backbone. The 3rd H normally in the functional group of cysteine bonds separately so is not included here. The more disulfide Bridges, the more stable the molecule will be. Hydrophobic interactions are the last additional Bond that tertiary structure proteins have. They are where nonpolar R groups ‘hide’ in the centre of the protein structure . See the booklet for a better description

29
Q

What is the polypeptide chain which has not specifically bonded to anything called in a tertiary structure protein?

A

The polypeptide backbone which can either be alpha helix or beta fitted sheet and sometimes can be changing mixture of both

30
Q

What are the four extra types of bonds in a tertiary structured protein?

A

More hydrogen bonds, ionic bonds, disulfide Bridges and hydrophobic interactions

31
Q

What bonds are the strongest middle and weakest in a tertiary structure protein?

A

Hydrogen

32
Q

What is the quarternary structure protein level?

A

Where two or more polypeptide chains are bonded together. For example a potassium channel is made up of four identical chains, each 97 amino acids long. Each chain is a protein, a polypeptide, so there are four proteins present but as the chains are identical, only one Gene is required.

33
Q

Describe a fibrous protein

A

The form long fibres. There have regular, repetitive sequences of amino acids. They are insoluble in water and play structural roles. They are strong and tough

34
Q

Describe a globularProtein

A

They fold up in a compact ball like shape. They are more water-soluble and have metabolic roles. They have a wide range of amino acid sequences in their structure. They are specific to their shape. Hydrophobic r groups on amino acids turn inwards towards the centre of protein and hydrophilic R groups go on the outside.

35
Q

What does haemoglobin do?

A

Haemoglobin transports oxygen in red blood cells.

36
Q

What structure level does haemoglobin have?

A

Haemoglobin is an example of a quaternary structure. It is made out of two lots of two different polypeptides, bonded mostly by disulphide Bridges. One of the types of polypeptide is called Alpha and the other beta. So we call the polypeptides alpha subunits and beta subunits.

37
Q

How does haemoglobin transport oxygen?

A

Each subunit, a polypeptide, contains a cofactor known as a haem group that includes an iron atom in the centre. The main component that binds with oxygen is the iron. There are four subunits in each haemoglobin. Therefore, each molecule of haemoglobin is capable of carrying four oxygen molecules.

38
Q

What is a prosthetic group?

A

A tightly bound, specific non polypeptide unit, required for the biological function of some protein. They are there non amino parts of a conjugated protein and are bonded to these polypeptides by covalent bonds or weak interactions. A haem is a prosthetic group.

39
Q

What are conjugated proteins? How does this link to haemoglobin?

A

Are proteins that function in interaction with other, non polypeptide chemical groups. Each polypeptide in haemoglobin is a conjugated protein that works with its own prosthetic haem group.

40
Q

What types of collagen are there?

A

There are lots of different types of collagen and most types are fibril structures.

41
Q

Describe the structure of a collagen triple helix in terms of it’s amino acids and physical shape and bonds

A

of 3 amino acids: glycine, hydroxyproline and proline. These three amino acids form a polypeptide chain where one in every 3 is glycine. Three of these ‘identical’ polypeptide chains then coil together in an alpha helix. Collagen has a long rigid structure made of the three polypeptides. It is sometimes called a triple helix or a triple helical structure. Each polypeptide alpha helix is held together by hydrogen bonds, forming the triple helix.

42
Q

Describe the structure of a collagen fibril

A

Triple helices line up parallel to each other and are cross-linked by covalent bonds.

43
Q

What is the function of collagen?

A

Collagen has a high tensile strength, due to its fibrous structure. It is present in skin, bone, tendons, blood vessels and cornea. This is type 1…?

44
Q

What shape is the hemoglobin molecule?

A

It is globular

45
Q

What molecule is the beta chain in haemoglobin like?

A

Myoglobin

46
Q

Haemoglobin + 4 oxygen molecules =?

A

Oxyhaemoglobin

47
Q

What conditions are needed to make oxygen separate from haemoglobin?

A

Low partial pressure of oxygen and the breakdown is made more efficient by presence of carbon dioxide or a low pH.

48
Q

What is the name given to the sequence of amino acids in a protein molecule?

A

Primary structure

Core Principles Eduqas Biology A Level (8 decks)

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