Chapter 5 - Cellular Function

Question 1

6 basic functions of proteins

Answer 1

1. maintain cell shape
2. coordinate changes inside and outside the cell via attachments to the cytoskeleton and extracellular matrix
3. receptors for chemical messengers from other cells (cellular communication via signal transduction)
4. enzymes that catalyze reactions
5. glycoproteins are involved in cellular recognition (help to recognize self as self and alert the immune system to intruders)
6. transport of substances across the membrane

Question 2

Passive transport

Answer 2

Involves either Diffusion or osmosis.

Diffusion - net movement of molecules from area of high [ ] to low [ ] until equilibrium is reached.
2 types of diffusion:
1) Simple
2) Facilitated

Osmosis - same as diffusion but with water.

Question 3

Facilitated diffusion

Answer 3

Polar and charged molecules require transmembrane proteins as carriers, or use ion channels to move through the lipid bilayer.

The molecules are attracted to the polar phospholipid head so they need to be carried across, or go through the protein channel.

Ex. Glucose, ions

Question 4

Simple diffusion

Answer 4

Non-polar and lipid soluble substances diffuse directly through the lipid bilayer.

Shouldn’t interact with the phospholipid polar heads since there is no charge to be attracted to.

Ex. Oxygen, O2

Question 5

Active transport

Answer 5

Substances cross the membrane moving against the concentration gradient and energy is required.

3 types:
- primary active transport
- secondary active transport
- vesicle transport

Question 6

Isotonic

Answer 6

The concentration of dissolved particles (solutes) is the same inside and outside of the cell

Question 7

Hypotonic

Answer 7

The concentration of dissolved particles is less than the concentration of water.

(Water rapidly flows in faster than it leaves-> cell may burst, aka hemolysis)

Question 8

Hypertonic

Answer 8

The concentration of dissolved particles is greater than the concentration of water in the cell.

(Water rapidly leaves faster than it enters-> cell may shrivel, aka crenation)

Question 9

Exocytosis

Answer 9

A way for large molecules to leave the cell

Question 10

Endocytosis

Answer 10

A way for large molecules to get inside of the cell.

3 types:
a) Phagocytosis - cell eating
b) Pinocytosis - cell drinking
c) Receptor mediated

Question 11

Energy

Answer 11

The capacity to cause change or perform work.

2 basic kinds:
- potential
- kinetic

Question 12

Potential energy

Answer 12

The energy that matter possesses as a
result of its location or structure (a compressed spring, an archery bow pulled back.

Chemical energy is the potential energy available for release in a chemical reaction – most important
energy for life.

Question 13

Kinetic energy

Answer 13

Energy associated with matter in motion.

Ex. The archery bow being released and the arrow shoots

Question 14

Exergonic reaction

Answer 14

An energy-releasing reaction.

The products of the reaction have less energy than the reactants do.

Ex. Respiration

Question 15

Endergonic reaction

Answer 15

An energy-requiring reaction.

The products of the reaction have more energy than the reactants

Ex. Photosynthesis

Question 16

Law of Energy Conservation

Answer 16

(The first law of thermodynamics)

The energy in the universe is constant. It can be transformed, but cannot be created or destroyed.

Question 17

The Entropy Law

Answer 17

(The second law of thermodynamics)

The entropy (randomness) of the universe is constantly increasing.

Question 18

Energy coupling

Answer 18

Then use of energy from exergonic reactions to drive endergonic reactions

Ex. Na+/K+ pump - energy used to pump 3Na+ out of the cell is also used to bring 2K+ into the cell

Question 19

Activation energy

Answer 19

The energy required to start a reaction.

Lowered by enzyme catalysts

Question 20

How do membranes form?

Answer 20

When mixed with water phospholipids will automatically form bilayers. This will surround areas of water, resulting in water filled bubbles, surrounded by lipid bilayers.

Question 21

Aquaporin

Answer 21

A protein associated with facilitated diffusion that creates a channel for water that can allow up to 3 billion water molecules to pass per second.

Question 22

Tonicity

Answer 22

The ability of a solution surrounding a cell which causes that cell to lose or gain water

3 kinds:
- isotonic
- hypotonic
- hypertonic

Question 23

Osmoregation

Answer 23

Describes a cells control their water balance to maintain homeostasis.

Ex. Fish gills are a form of osmoregulation

Question 24

Metabolism

Answer 24

All the thousands of exergonic and endergonic reactions on the body

Question 25

Metabolic pathway

Answer 25

A series of chemical reactions that builds or breaks down complex molecules.

Question 26

Substrate

Answer 26

A specific substance on which an enzyme acts on

Question 27

Active site

Answer 27

Where the substrate binds into a pocket of the enzyme.

Associated with R groups

Question 28

Cofactors

Answer 28

Non-protein molecules / ions that are required for proper functioning of the enzyme. They will bind to the active site and aid the enzyme.

Ex. Zn, Cu, Fe

If it is organic = coenzyme

Question 29

Vitamins

Answer 29

Substances that are necessary for life, but that we have lost the ability to synthesize.

Help in making coenzymes

Question 30

Competitive inhibitors

Answer 30

When the inhibitor binds to the active site of the enzyme, and competes with a substrate for that active site.

Question 31

Noncompetitive inhibitors

Answer 31

Binds to the enzyme at another location (aka an allosteric site), and changes the shape of the enzyme so the active site no longer fits the substrate.

Question 32

Feedback inhibition

Answer 32

Sometimes inhibitors are good things:

Feedback inhibition will shut off a metabolic pathway once there is enough product produced (it acts as an inhibitor of the enzyme to stop it from wasting too much energy)

Examples: antidepressants, blood pressure meds, advil

Question 33

System

Answer 33

Refers to what you are studying

Question 34

Surroundings

Answer 34

Refers to everything that exists outside of the system that you are studying

Question 35

Proenzyme

Answer 35

Enzymes in the body that are produced in an inactive form. (Usually these come before the actual enzyme: precursor of the enzyme)

Ex. Pepsin is inactive at first to protect cells from being digested, but will eventually activate to digest proteins in the stomach

Question 36

When two aqueous solutions that differ in solute concentration are placed on either side of a semi permeable membrane and osmosis is allowed to take place, the water will…

Answer 36

Exhibit a net movement to the side with lower free water concentration.