Vce Biology: Proteins And Enzymes

Front 1

What are amino acids composed of?

Back 1

An amino group (NH2) and a carboxylic acid group (COOH).

Front 2

What is the primary structure of a protein?

Back 2

It is its amino acid sequence. The sequence of amino acids is unique for each protein.

Front 3

How do bonds form between each amino acid? And what type of bonds are they?

Back 3

They are formed by a condensation reaction (water is lost). Covalent bonds form between a carbon atom of one amino acid and the nitrogen atom of the next. These carbon-nitrogen links are called peptide bonds. They are very strong.

Front 4

Where do polypeptide bonds occur in the chain?

Back 4

They occur where the structure of the amino acid is constant.

Front 5

What is a secondary structure of a protein?

Back 5

Hydrogen bonds between hydrogen and oxygen bonds cause the peptide chains to either coil or pleat. This forms a proteins secondary structure.

Front 6

What are the two common forms of a secondary structure?

Back 6

The alpha helix and the beta pleated sheet.

Front 7

What is a alpha helix?

Back 7

The alpha helix is coiled. The loops of the helix are formed when hydrogen atoms form one part of the molecule's backbone from hydrogen bonds with oxygen atoms from another part of the chain. Proteins that consist of alpha helices tend to be elastic.

Front 8

What is a beta pleated sheet?

Back 8

Also formed by hydrogen bonding between hydrogen and oxygen atoms, parts of the peptide chain fold back to align with neighbouring parts of the chain. Proteins that consist largely of beta pleated sheets are not elastic and doesn't sag.

Front 9

Can a secondary structure be composed of both beta pleated sheets and alpha helices?

Back 9

Yes, it is not uncommon for a protein to have both alpha helices and beta pleated sheets.

Front 10

What is a tertiary structure of a protein?

Back 10

It is its overall three-dimensional shape. A completed protein contains many loops and folds.

Front 11

How is the tertiary structure of a protein determined?

Back 11

By four factors:

- Hydrogen bonding between atoms in some R groups, and between atoms of the hydrophillic amino acids and the surrounding water.

- Ionic bonding between atoms in R groups that are electrically charged.

- Covalent bonding between the sulfur atoms of some R groups.

- Hydrophobic interactions in which R groups that are hydrophobic are repelled by the water surrounding proteins in the cell, and so tend to collect on the inside of the protein molecules.

Front 12

What is the quaternary structure of a protein?

Back 12

Some biologically active proteins consist of more than one polypeptide chain, held together by interactions between atoms in the separate polypeptide chains.

Front 13

What structure of a protein is most stable?

Back 13

The primary structure of a protein is the most stable.

Front 14

Can proteins become non-functional? How?

Back 14

Yes, they can be disrupted by changes in the pH of the surrounding liquid, heat, or by the presence of other chemicals. This results in the protein losing its secondary or tertiary structure and thus is becomes denatured.

Front 15

What groups are proteins divided into?

Back 15

They are divided into two major groups, fibrous proteins and globular proteins.

Front 16

What are fibrous proteins?

Back 16

They are important in cellular structure, and include muscle proteins that can contract, proteins that strengthen tendons and ligaments, keratin in nails and skin, and proteins that aid in blood clotting.

Front 17

What are globular proteins?

Back 17

They include all enzymes, antibodies, many hormones and the proteins that make up cilia and flagella.

Front 18

What is another function of a protein?

Back 18

Proteins acts as channels for the movement of substances in and out of cells, and as receptor sites for hormones and other cellular messengers.

Front 19

What are glycoproteins?

Back 19

Proteins that are combined with carbohydrates. They are found on the surface of eukaryotic cells and are important in adhesions (sticking cells together) and recognition.

Front 20

What is a proteome?

Back 20

It is the sum total of all proteins found in a functioning organism.

Front 21

What is the study of proteomes called?

Back 21

Proteomics.

Front 22

What is a catalyst?

Back 22

It is any chemical that speeds up the rate of a chemical reaction without itself being used up in the reaction.

Front 23

What is an enzyme?

Back 23

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