Human Biochemistry

Question 1

What is metabolism?

Answer 1

The sum total of the metabolic reactions reactions in the body

Question 2

Give two units that convey energy value of its food content.

Answer 2

calories, joules

Question 3

What is a bomb calorimeter?

Answer 3

Measures the heat of combustion reactions

Question 4

What is the formula for energy?

Answer 4

mass (g) x specific heat capacity x temperature change

Question 5

If given the mass of food and the volume of water and temperature change, how do you calculate the energy value of the food in kjg^-1?

Answer 5

First solve for energy using the q=mct. Then divide q by the mass in grams of the food.

Question 6

List major functions of proteins in the body.

Answer 6

Structural
Hormones
Immunoproteins
Transport
Enzyme
Energy

Question 7

Describe the structural role of proteins.

Answer 7

Make up the building blocks for our body. Makes up our structure.

Example:
Keratin - in hair and fingernails
Collagen - connective tendons in skin and tendons
Myosin - contractile action in muscles to bring about movement

Question 8

Describe proteins as enzymes.

Answer 8

They are catalysts that lower the activation energy. This increases the rate of reaction.

Ex. Lactase hydrolyzes lactose into glucose and galactose.

Question 9

Describe proteins as hormones

Answer 9

They control and regulate bodily functions by sending chemical messages into the blood stream.

Ex. Insulin - signals the cells to bring glucose from the blood stream into the cell.

Question 10

Describe proteins as immunoproteins.

Answer 10

act as antibodies which help destroy foreign proteins in the blood

Question 11

Describe proteins in their transportation roles.

Answer 11

move specific molecules throughout the body.

ex: hemoglobin- carries oxygen from the lungs to all respiring cells.

Question 12

Name the functional groups of amino acids.

Answer 12

Central carbon is surrounded by a hydrogen, a amino group, a R group and a carboxylic acid.

Question 13

How are amino acids characterized?

Answer 13

They are classified according to the chemical nature of their R group.

Question 14

..Wait. What are amino acids?

Answer 14

Amino acids have properties similar to ionic compounds. ie- they are crystalline compounds with high melting points. Have a much greater solubility in water than in non polar solvents.

Question 15

What’s the significance of AA’s having properties similar to ionic compounds?

Answer 15

Suggests that AAs exists as dipolar ions, or commonly known as zwitterions.

Question 16

What is a zwitterion?

Answer 16

A group of atoms with a positive and negative charge.

Question 17

How does a zwitterion form?

Answer 17

Result of internal acid-base reaction in an amino acid.

The H+ is transferred from the -COOH group and added to the NH2 group to form NH3.

Question 18

Ok. Why is a zwitterion important?

Answer 18

It allows the protein to be amphoteric. duh.

Question 19

Since amino acids are amphoteric they are able to act as…

Answer 19

buffers. Helps maintain pH in our body.

Question 20

In terms of pH, characterize a positive. neutral, and negative ion.

Answer 20

Positive ion - low pH
Neutral ion - at its isoelectric point, no net pH, least soluble at this point
Negative Ion - higher pH

Question 21

How do amino acids link together?

Answer 21

Through a condensation reaction between the acid group of one amino acid and the amino group of another amino acid. Water is eliminated. This bond is known as a peptide bond.

Question 22

What is the primary structure of a protein?

Answer 22

The amino acid sequence. Sets foundation for the formation of following structures.

Question 23

What is the secondary structure of proteins?

Answer 23

Regular hydrogen bonding. Hydrogen bonding can occur between amino acid molecules to produce alpha helix (spiral) or the beta pleated sheet.

Question 24

Describe te a-helix spiral.

Answer 24

It’s a spiral. Flexible and elastic because the hydrogen bonds break easily. “intra-chain” h-bonds

Good example is in keratins.

Question 25

Describe the b-pleated sheet.

Answer 25

Composed of “side-by-side” polypeptides. “inter-chain” h bonds.

Flexible, not elastic.

Question 26

What is the tertiary structure of proteins?

Answer 26

Refers to the 3D shape created due to the interactions between the R groups of amino acids. This 3D shape is called conformation.

Question 27

Compare and contrast fibrous and globular proteins.

Answer 27

Fibrous - tough, insoluable

Globular - water soluble.

Question 28

Name some interactions that occur between R groups in the tertiary structure.

Answer 28

1. Hydrophobic interactions - between non-polar side chains.
2. Hydrogen bond - between polar
3. Ionic bond - between side chains carrying a charge
4. Disulfide bridges - between sulfide atoms in the amino cysteine