chapter 4

Question 1

What is a cellular membrane?

Answer 1

A barrier that separates the cell from its surroundings.

Question 2

What does cellular membrane consist of?

Answer 2

Fatty-acid-based lipids and proteins.

Question 3

Fluid mosaic model membranes

Answer 3

They consist of a fluid lipid bilayer in which proteins are embedded and float freely

Question 4

Polarity

Answer 4

Uneven distribution of a charge

Question 5

Two major factors influencing proper fluidity

Answer 5

1. The makeup of lipid molecules
   - Degree of unsaturation of fatty acid tails
   - Presence of sterols
2. Temperature

Question 6

Saturated fatty acids

Answer 6

• Each carbon is fully bonded to hydrogens with only single bonds.
• Straight shape
• Tighter packing
• Solid at room temp. Ex. Butter

Question 7

Unstaurated fatty acids

Answer 7

• Double-bonds between carbons
  introduce kinks
• Less dense packing
• Liquid at room temp . Ex. Vegetable oil

Question 8

Sterols acting as membrane buffers

Answer 8

At high temps sterols help to restrain movement of lipids, thus preventing membrane from becoming too fluid

Question 9

Integral Membrane Proteins

Answer 9

• Proteins embedded in phospholipid bilayer
• Composed of nonpolar amino acids

Question 10

Peripheral membrane proteins

Answer 10

• On surface of membrane
• Do not interact with hydrophobic core
• Held together by noncovalent bonds
• Many on cytoplasmic side of membrane
• Made up of mixture of polar and non-polar amino acids

Question 11

Passive membrane transport

Answer 11

-Movement of molecules across a membrane without using energy like ATP
- Driven by diffusion

Question 12

Diffusion

Answer 12

Net movement of substance from region of higher to lower concentration

Question 13

Simple diffusion

Answer 13

A way to move substances across cell membranes without using energy.

Question 14

Facilitated diffusion

Answer 14

Molecules moving across a membrane with a transporter’s help.

Question 15

Osmosis

Answer 15

Passive diffusion of water molecules

Question 16

Exocytosis

Answer 16

• Moves through the cytoplasm and contacts the plasma membrane
• Transports things in bulk such as Neurotransmitters and Proteins

Question 17

Endocytosis

Answer 17

• Encloses materials outside the cell in the plasma membrane
• Pockets inward and forms endocytic vesicle on cytoplasmic side

Question 18

Phagocytosis

Answer 18

cell-eating; ex. white blood cells

Question 19

Why is signaling important?

Answer 19

The ability to detect and react to changes in the environment is a key feature of life.

Question 20

Intracellular receptors

Answer 20

• Found in Nucleus OR Cytoplasm
• Steroid hormone receptors (ex.hormone- binding domain & DNA-binding domain)

Question 21

Phosphorylation

Answer 21

The addition of a phosphoryl (PO3) group to a molecule

Question 22

Amplification

Answer 22

The act or result of increasing in size or effect

Question 23

Desaturase

Answer 23

Turns saturated fatty acids into unsaturated fatty acids

Question 24

4 key functions of membrane proteins

Answer 24

1. Transport
2. Enzymatic activity
3. Signal transduction
4. Attachment/ recgonition

Question 25

Primary active transport

Answer 25

The protein moves molecules and uses ATP for energy

Question 26

Secondary active transport

Answer 26

The transport uses ion concentration gradients as energy, indirectly relying on ATP.

Question 27

the 5 essential elements for cell signalling or communication

Answer 27

- Signal - Receptor - Signal transduction - Response - Termination

Question 28

3 points in cell communication

Answer 28

1. Extracellular signal molecules 2. Surface receptors that receive the signals 3. Internal response pathways that are triggered when receptors bind a signal

Question 29

Signal transduction pathways

Answer 29

A series of events that start when a signalling molecule binds to a receptor, triggering cell processes.

Question 30

Protein kinases

Answer 30

Pass signals by triggering a chain of phosphorylation reactions, called a cascade.