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Biology A Level > Topic 1A- Biological Molecules (Proteins) > Flashcards

Topic 1A- Biological Molecules (Proteins) Flashcards

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1
Q

What are proteins made up of

A

Long chains of amino acids

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2
Q

What do you call two amino acids joined together by a chemical bond

A

Dipeptide

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3
Q

What do you call more than two amino acids joined together by chemical bonds

A

Polypeptide

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4
Q

What is a protein

A

One or more polypeptide

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5
Q

How many different amino acids are there and what makes them all different

A

There are 20 different amino acids and what makes them different is they all have different R groups

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6
Q

Draw the general structure of an amino acid

A
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7
Q

What are the 3 groups in an amino acid

A

Amine group (H2N)
Variable group (R)
Carboxyl group (COOH)

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8
Q

What type of reaction forms polypeptides? Explain what happens and what type of bond is formed and where.

A

Condensation reactions

The OH from one amino acid’s carboxyl group reacts with the H on another’s amine group to form a water molecule, and a peptide bond is formed between the Carbon and Nitrogen.

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9
Q

When does the reverse reaction to the peptides being formed happen

A

During digestion

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10
Q

What are the four protein levels

A

1) Primary structure
2) Secondary structure
3) Tertiary structure
4) Quaternary structure

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11
Q

Give the definition of the primary structure

A

The number and sequence of amino acids in the polypeptide chain

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12
Q

Explain what the secondary structure is and how this occurs

A

This is when the alpha helixes and beta pleated sheets form because of hydrogen bonding between carboxyl and amino groups in the peptide backbone. Certain amino acids tend to form an alpha helix, while others tend to form a beta-pleated sheet.

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13
Q

Explain what the tertiary structure is and how this happens

A

This is the further folding of the polypeptide chain. The tertiary structure is formed by interactions between the R groups on the amino acids, such as hydrogen bonds, disulfide bridges, ionic bonds and hydrophobic interactions. This causes the chain to coil and fold even further

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14
Q

How do ionic bonds occur on polypeptides

A

This is electrostatic forces of attraction between oppositely charged parts of the molecule

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15
Q

How do disulfide bridges occur

A

They happen whenever two molecules of the amino acid ‘cysteine’ come close together - the sulfur atom in one cysteine covalently bonds to the sulfur atom in the other.

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16
Q

What is the quaternary structure of a protein

A

some proteins are made of several different polypeptide chains held together by bonds (often disulfide bridges). The Quaternary structure is the way these polypeptide chains are assembled together.

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17
Q

Draw the general structure of an amino acid

A
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18
Q

What is an amine group

A

NH2

19
Q

What is a carboxyl group

A

COOH

20
Q

What are the elements found in amino acids

A

All have Carbon, Hydrogen and oxygen nitrogen

Some have sulfur

21
Q

What do the ends of a chain of amino acid always look like

A

One end always has a free amine group and the other always has a free carboxyl group

22
Q

What type of bonds joins the primary structure together in proteins

A

Peptide bonds

23
Q

How do you know the number of peptide bonds In a polypeptide chain

A

It’s the number of amino acids - 1

24
Q

What are the strongest type of bond in the tertiary structure of proteins and why

A

Disulfide bridges are the strongest as they are a covalent bond between two amino acids containing sulfur

25
Q

Describe the structure of haemoglobin

A

They contain 4 polypeptides :
2 alpha chains
2 beta chains
They also contain the 4 prosthetic groups (which means it’s not protein) we call this a haem group (it’s Fe2+)

This prosthetic group binds to an oxygen molecule.

26
Q

Give the definition of a quaternary structure

A

2 or more polypeptide chains held together to carry out a specific function

27
Q

Give the steps of how to test a food for proteins

A

Biuret test:

1) Mix the food sample with distilled water using a pestle and mortar, and add it to a test tube.

2) Your solution must be alkaline, so Add sodium hydroxide solution and mix carefully.

3) Add a few drops of copper (II) sulfate solution and leave the solution for 5 minutes.

4) If protein is present, the solution will turn purple. If there is no protein present, the solution will stay blue.

28
Q

Explain how a dipeptide is formed

A

This is formed by the condensation of two amino acids, forming a peptide bond between them.

The condensation reaction occurs between one amine group (NH2) and one carboxyl group (COOH), to form a peptide bond via the removal of water.

29
Q

What type of reaction forms dipeptides

A

Condensation reactions

30
Q

What type of reaction breaks down dipeptides

A

Hydrolysis reaction

31
Q

What is at each end of any chain of amino acid

A

There’s always a free amine group and a free carboxyl group

32
Q

Explain why the structure of a protein is determined by the relative position of amino acids

A

Because the bonds formed (hydrogen bonds, disulfide bridges, ionic bonds and hydrophobic interactions) are determined by the position of the R groups, which are determined by the primary structure

33
Q

What shape usually are enzymes and why

A

Spherical due to the tight folding of the polypeptide chains.

34
Q

Are enzymes soluble or insoluble

A

Soluble

35
Q

What is the word that means an enzymes active site is similar shape to the substrate

A

Complementary

36
Q

What are antibodies made up of

A

Two light (short) polypeptide chains and two heavy (long) polypeptide chains bonded together

37
Q

What is the structure of transport proteins and why

A

They are made up of hydrophobic and hydrophilic amino acids, which cause the protein to fold up and form a channel. These proteins transport molecules and ions across cell membranes

38
Q

Describe the structure of structural proteins and explain why

A

They are physically strong, so they consist of long polypeptide chains lying parallel to each other with cross - links between them.

39
Q

What does a polar and non-polar molecule mean?

A

Polar= molecules with a uniform distribution of electron density across the whole molecule

Non-polar= molecules with an unequal distribution of electrons density across the whole molecule

40
Q

What is the simplest amino acid

A

Glycine

41
Q

What is the R group of glycine

A

Hydrogen

42
Q

What methods can be used to separate a mixture of amino acids

A

Paper chromatography

43
Q

What determines the distance travelled by amino acids in paper chromatography

A

Their size and charge

44
Q

What type of structure do antibodies have

A

Quaternary structure

Biology A Level (7 decks)

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