Cell Theory

Question 1

What are the basic principles of cell theory

Answer 1

1. The cell is the smallest functional living unit
2. Organismal functions depend on individual and collective cell functions
3. Biochemical activities of cells are dictated by their specific sub cellular structures
4. All cells arise from preexisting cells

Question 2

What are the two types of membrane proteins?

Answer 2

1. Integral (transmembrane) proteins
2. Peripheral proteins

Question 3

Integral Proteins

Answer 3

Firmly inserted into the cell membrane

Question 4

Peripheral Proteins

Answer 4

Adhere to inner or outer surface of the cell membrane but are NOT inserted into the cell membrane (may be loosely attached to integral proteins)

Question 5

What are the 6 functions of membrane proteins (describe them)?

Answer 5

1. Transport (channels)
2. Receptors for signal transduction
3. Attachment of cytoskeleton and extracellular matrix
4. Enzymatic activity
5. Intercellular joining
6. Cell-cell recognition

Question 6

What are the different types of membrane junctions?

Answer 6

• Tight junctions: impermeable
• Desmosomes: impermeable AND good for anchoring cells together
• Gap junctions: allow small molecules/ions to pass

Question 7

What are the two types of membrane transport?

Answer 7

1. Passive Tranport
2. Active Transport

Question 8

What are some examples of passive transport?

Answer 8

1. Simple diffusion
2. Facilitated diffusion (carrier/channel mediated)
3. Osmosis

Question 9

Simple diffusion

Answer 9

Nonpolar (hydrophobic substances) will diffuse directly through the phospholipid bilayer

Question 10

Facilitated diffusion

Answer 10

• Use either carrier (binding changes shape) or channel proteins (leakage, gated, aqueous) that exhibit specificity
• Can be regulated in terms of activity and quantity
  What determines the rate (slide 20)

Question 11

Osmosis

Answer 11

Movement of water across a selectively permeable membrane

Question 12

Solute and water molecules move ___ their concentration gradients in ___ directions.

Answer 12

Down, Opposite
Water will move from an area of low solute concentration to an area or high solute concentration

Question 13

What is tonicity?

Answer 13

The ability of a solution to cause water to move into or out of a cell

Question 14

Isotonic

Answer 14

The solution has the same solute concentration as the cytosol
What happens to a cell in a isotonic solution

Question 15

Hypertonic

Answer 15

A solution having a greater solute concentration than that of the cytosol
What happens to a cell in a hypertonic solution

Question 16

Hypotonic

Answer 16

A solution having lesser solute concentration than that of the cytosol
What happens to a cell in a hypotonic solution

Question 17

What are some examples of active transport?

Answer 17

• Primary active transport
• Secondary active transport
• Vesicular transport
  How are you moving solutes in active transport?

Question 18

Primary active transport

Answer 18

Energy from the hydrolysis of ATP causes a conformational change in the transport protein that causes solutes to be “pumped” across the membrane
(Ex: Sodium-Potassium pump)

Question 19

Secondary active transport

Answer 19

Carrier depends on concentration gradient created by primary active transport somewhere else in the cell
(Ex: Sodium-glucose symport transport)
Does this type of transport utilize ATP?

Question 20

What are some examples of vesicular transport?

Answer 20

• Endocytosis: transport into the cell (phagocytosis, pinocytosis, receptor-mediated endocytosis)
• Exocytosis: transport out of the cell
• Transcytosis: Transport across then out of the cell (combination of endocytosis and exocytosis)

Question 21

Phagocytosis

Answer 21

The cell engulfs a large particle by forming pseudopods around it (“cell eating”)

Question 22

Pinocytosis

Answer 22

The cell “gulps” drops of extracellular fluid containing solutes into tiny vesicles (“cell drinking”)

Question 23

Receptor-mediated endocytosis

Answer 23

Solute particles bind to receptors on the plasma membrane and are taken into the cell in a clathrin-coated vesicle with minimal extraneous matter

Question 24

Describe exocytosis

Answer 24

A vesicle approaches the cell surface and fuses with the plasma membrane (via proteins at the vesicle surface) a pore opens up and vesicle contents are released to the cell exterior

Question 25

What establishes resting membrane potential

Answer 25

- Facilitated diffusion of K+ into and out of the cell - Negative membrane potential is achieved when movement of K+ into the cell = movement of K+ out of the cell

Question 26

How is RMP maintained?

Answer 26

The sodium-potassium pump continuously ejects NA+ (3) out of the cell and carries K+ (2) into the cell maintaining the negative charge on the inner plasma membrane face

Question 27

What is the purpose of cell adhesion molecules?

Answer 27

- Anchor cells to the extracellular matrix and to each other - Simulate synthesis or degradation of junctions - Transmit signals to cells

Question 28

What is the role of integral proteins on the cell surface

Answer 28

- Contact signaling: touching and recognition of cells - Chemical signaling: interaction between receptors and ligands