Labs 4&6 Review

Question 1

Lock & Key hypothesis: enzyme must exhibit the appropriate _________, _____________, and __________ to fit together perfectly with the substrate

Answer 1

3d shape, matching charges, and correct size

Question 2

Lowering the activation energy of a reaction can increase the reaction rate because it increases:

Answer 2

likelihood of reaction occurng

Question 3

In lab 4 [enzyme activity] why was the rate of increase in absorbance rapid at first, but then slowed down?

Answer 3

Substrates became used up, so odds of reaction declined and fewer reactions occured toward the end

Question 4

In lab 4, what was the effect of enzyme concentration on reaction rate?

Answer 4

The higher the enzyme concentration, higher odds of reaction occuring, so reaction rate increased

Question 5

Enzymes are not used up in the reaction, so why does changing enzyme concentration affect reaction rates?

Answer 5

If there is only 1 enzyme, only 1 substrate binds at a time; so if there are many enzymes, many substrates can bind, leading to more product

Question 6

Why do the heat treated (then cooled) and the acidic enzyme not function as effectively?

Answer 6

The acidity/ heating leads to denaturation [breaking of hydrogen bonds] of the enzyme [changes its 3d shape, so substrate can’t bind]

Question 7

What is the physiological significance of enzymes in our cells?

Answer 7

They increase rate of chemical reactions/cell processes

Necessary for survival, in order to make enough products

Question 8

Why does hotter temperature lead to faster diffusion?

Answer 8

Due to increase of kinetic energy; warmer molecules move quicker

Question 9

Why does lighter weight of molecule lead to faster diffusion?

Answer 9

Heavy molecules move slower, leading to slower diffusion

Question 10

Why do lower density of medium (higher permeability) lead to faster diffusion?

Answer 10

The more permeable, the easier molecules can diffuse through the membrane

Question 11

Define osmosis

Answer 11

the passive movement of water/solvent molecules through a semi permeable membrane from an area of low to high solute concentration until equilibrium is reached

Question 12

Did 20% or 40% sucrose exert a greater osmotic pressure?
Why?

Answer 12

40%

High concentration = higher osmotic pressure, due to higher concentration gradient between sucrose and water

Question 13

In lab 6 about osmosis, why does the rate of osmosis slow down?

Answer 13

Due to decreased gradient as solute concentration changes

Question 14

Molecular weight has a big impact on:

Answer 14

simple diffusion

[lighter = faster]

Question 15

Does concentration of one solute molecule inlfuence rate of diffusion of a different solute molecule?

Answer 15

NO

Each molecule is treated independently [unless they are charged]

Question 16

Red blood cells will ________ when placed in a hypertonic solution

Answer 16

crenate

Question 17

You can rehydrate desiccated cells by placing them in:

Answer 17

Hypotonic solution

Question 18

A 0.1 NaCl solution is _____________ to a 0.1 M glucose solution

Answer 18

hypertonic

[NaCl has 2 osmoles = 0.2 Osm, glucose is 0.1 osm)

Question 19

What must happen to a fluid to change it to a hypertonic urine?

Answer 19

Remove water (or add solute)

Question 20

How would dehydration lead to sense of thirst?

What effect would drinking seawater have on sense of thirst?

Answer 20

Dehydration leads to hypertonic blood, stimulating osmoreceptors

Drinking seawater would increase solute concentration, and will not relieve thirst