Chapter 1: Biological Molecules

Question 1

1.5 Enzymes

An enzyme is a ____ protein

Answer 1

Globular

Question 2

1.5 Enzymes

What are the key characteristics of an enzyme?

Answer 2

• Globular proteins
• Water soluble
• Act as biological catalysts (speed up reactions without being used up themselves)
• Highly specific
• Have an ‘active site’
• Activitiy is usually affected by pH and temperature

Question 3

1.5 Enzymes

What is the primary structure of an enzyme?

Answer 3

Their primary structure is the initial chain of AA’s.

Question 4

1.5 Enzymes

What is secondary structure of an enzyme?

Answer 4

The secondary structure is the initial folding.

Question 5

1.5 Enzymes

What is tertiary structure of an enzyme?

Answer 5

Tertiary structure is its functional shape with hydrophobic groups in the middle and hydrophilic groups surrounding them on the outside.

Question 6

1.5 Enzymes

Draw a diagram for enzyme action

Answer 6

Question 7

1.5 Enzymes

Question 8

1.5 Enzymes

What is lock and theory model?

Answer 8

The enzymes specifically shaped active site will only allow one kind of substrate to fit in.
The substrate has to have a complimentary shape to the active site therefore can fit in.

Question 9

1.5 Enzymes

What is the induced fit hypothesis?

Answer 9

Once in the active site the substrate is broken down, this process is aided by the ‘induced-fit hypothesis’. This suggests that the enzyme active site is malleable to fit the shape of the substrate. The enzyme will change shape slightly to hold the substrate in place, this change puts stress on the substrate further speeding up the process

Question 10

1.5 Enzymes

Draw the enzyme action activation energy curve

Answer 10

Question 11

1.5 Enzymes

Why does pH affect enzyme action?

Answer 11

A hydrogen (H+) ion carries a positive charge so is attracted to negative charges. And likewise repelled by positive charges.
Hydrogen and ionic bonds are responsible for maintaining the tertiary structure and repulsion or attraction may alter tertiary structure.
Some ‘R’ groups are slightly charged and therefore will be attracted/repelled by the presence of H+ ions.

Question 12

1.5 Enzymes

The intial rate is always…

Answer 12

…the highest.Maximum number of active sites available when compared to number of substrates.

Question 13

1.5 Enzymes

Draw the three types of enzyme Inhibtion

Answer 13

Question 14

1.5 Enzymes

Describe competitive inhibition

Answer 14

**The inhibitor competes with the substrate for the active site of the enzyme. **
Inhibitor is structurally similar to the substrate, binding to the active site. When the inhibitor binds, substrate cant bind, decreasing RoR

The presence of a competitive inhibitor can be overcome by increasing the concentration of the substrate. As more substrate molecules are available, they are more likely to outcompete the inhibitor

Question 15

1.5 Enzymes

Describe non competitive inhibition

Answer 15

**In non-competitive inhibition, the inhibitor binds to a different site on the enzyme, not the active site. This other site is called the allosteric site.
**
Inhibitor binds to the allosteric site, causing a conformational change in the enzyme. This change can either reduce the enzyme’s ability to bind to the substrate or lower the catalytic activity
- this MAY permenantly alter the enzymes shape making it inactive
Cant be overcome by increasing concentration of substrates

Question 16

1.5 Enzymes

Describe uncompetitive inhibition

Question 17

1.7i Water-Understand the importance of the dipole nature of water

Draw a molecule of water

Answer 17

2 hydrogens 1 oxygen with 2 lone pairs on oxygen giving it a positive charge.

Question 18

1.7i Water-Understand the importance of the dipole nature of water

Draw the hydrogen bonding of water to other water molecules

Answer 18

dotted line from hydrogen with sigma+ to oxygen sigma -

Question 19

1.7 Water-Understand the importance of the dipole nature of water

Why is water a good solvent?

Answer 19

Because water is dipolar it allows chemicals to dissolve readily and easily, this makes it an ideal transport medium.

Question 20

1.7i Water-Understand the importance of the dipole nature of water

What is the temperature at which water is most dense?

Answer 20

At 4°C, water’s dipole properties allow hydrogen bonds to form a more efficient arrangement, maximizing molecular packing. Below this temperature, water molecules form an open hexagonal structure due to hydrogen bonding, reducing density. Thus, water reaches its maximum density at 4°C before expanding upon freezing.

Question 21

1.7i Water-Understand the importance of the dipole nature of water

Why does water have surface tension?

Answer 21

Water’s dipole nature leads to strong hydrogen bonding between molecules at the surface, creating a cohesive “film” that resists external forces. This cohesive force, due to the alignment of water molecules, results in surface tension, allowing small objects to float and insects to walk on water.

Question 22

1.7i Water-Understand the importance of the dipole nature of water

Discuss waters high specific heat capacity?

Answer 22

Water’s dipole nature creates strong hydrogen bonds between molecules, requiring significant energy to break. This extensive hydrogen bonding means that water can absorb a lot of heat energy before its temperature rises, resulting in a high specific heat capacity. This property stabilizes temperatures in living organisms and environments.

Question 23

1.7i Water-Understand the importance of the dipole nature of water

Discuss the incompressible nature of water

Answer 23

Incompressibility means that water does not significantly change in volume when a force is applied to it. This property is crucial for:
Structural support: Water in cells and tissues provides structural support and shape to organisms.
Buoyancy: The incompressibility of water allows aquatic organisms to float and move more easily.