Chapter 3: Cells

Question 1

Cells

Answer 1

The basic units of living organisms

Consist of 3 main parts:
1) plasma membrane
2) cytoplasm
3) nucleus

Question 2

Plasma membrane

Answer 2

Separates the intercellular from extracellular fluid.

Contains phospholipids

Function: semipermeable barrier that regulates the flow of material into and out the cell.

Question 3

Fluid mosaic model

Answer 3

Describes the the plasma membrane;

A “sea” of phospholipids (bilayer) always moving with various proteins within the fluid

Question 4

Integral (transmembrane) proteins

Answer 4

Proteins in the plasma membrane that extend through the phospholipid bilayer (usually to transport molecules in and out)

Question 5

Peripheral membrane proteins

Answer 5

Associated loosely with only one side of the membrane

Question 6

Membrane protein functions

Answer 6

• transport (as a channel or a carrier) of molecules in an out of the cell
• receptor for chemical messengers
• enzymes to catalyze reactions
• identifiers of what cell it is
• anchoring the cytoskeleton

Question 7

Membrane junctions

Answer 7

Provides contact or adhesion between 2 neighbouring cells so they can communicate.

3 types;
- Gap junction (communicators)
- Tight junction (impermeable)
- Desmosomes (anchoring)

Question 8

Gap junctions

Answer 8

The transmembrane proteins form a tiny fluid filled channels called connexons to connect to neighbouring cells.

They allow ions and small molecules to diffuse the cytosine of one cell to another (they communicate)

Question 9

Tight junctions

Answer 9

Plasma membranes of adjacent cells are fused together by transmembrane proteins

They are impermeable therefore materials cannot pass through them

Question 10

Desmosomes

Answer 10

The intermediate filaments of adjacent cells create a net-like structure to prevent cells from separating, which contributes to the stability of the tissue.

Question 11

Selectively permeable

Answer 11

The cell membrane allows only certain things through.

Usually nonpolar, uncharged, and small molecules can. (And water). But ions, charged, and polar molecules cannot.

Question 12

Membrane transport

Answer 12

The process of transporting substances across membranes.

2 types:

• Passive transport (substances move down their [ ] gradients, from area of high [ ] to area of low [ ], and energy is not required.)
• Active transport (substances move against the [ ] gradient, from area of low [ ] to area of high [ ], and energy is required.)

Question 13

Passive transport

Answer 13

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 14

What is diffusion rate affected by?

Answer 14

• Temperature (high temp = faster)
• [ ] gradient (bigger = faster)
• Distance (shorter distance = faster)
• Particle size (smaller = faster)
• Surface area (more SA = faster)

Question 15

Simple diffusion

Answer 15

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 16

Facilitated diffusion

Answer 16

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 17

Osmotic pressure

Answer 17

The ability of a solution to attract or draw in water.

(The greater the number of solute particles in a solution, the great the osmotic pressure)

Question 18

Hypotonic solution

Answer 18

There is less [ ] of dissolved particles and more [ ] of water molecules.

i.e. Water rapidly enters the cell via osmosis faster than it leaves. This causes the cell to burst = hemolysis of RBC’s

Question 19

Hypertonic solution

Answer 19

There is a higher [ ] of dissolved particles, and less [ ] of water molecules.

i.e. Water rapidly leaves the cell faster than it enters. This causes the cell to shrivel and die = crenation of RBC’s

Question 20

Tonicity

Answer 20

The ability of a solution to modify the volume of cells by altering the water content.
3 types:
- hypotonic
- hypertonic
- isotonic (no change)

Question 21

Active transport

Answer 21

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

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

Question 22

Primary active transport

Answer 22

Energy from ATP hydrolysis changes the shape of a transported protein (opens and closes the channel), and it “pumps” the substance across the membrane.

(Uses ATP directly)

Question 23

Secondary active transport

Answer 23

Transport of 2 molecules using energy supplied by an ion gradient given by a primary active transport pump.

(Indirectly latches onto used ATP)

2 types:
Antiporter - things transported are going the opposite direction
Symporter - things transported are going the same direction

Question 24

Vesicle transport

Answer 24

Only used for macromolecules, and fluid.

2 types:
Exocytosis - vesicle is moved out of the cell by fusing with the cell membrane and releases its contents.

Endocytosis - moves material into the cell by forming a vesicle

Question 25

Secretory vesicle

Answer 25

A vessel of the Golgi complex that will fuse with the cell membrane, then proteins are released via exocytosis

Question 26

Membrane vesicle

Answer 26

A vesicle of the Golgi complex that fuses with membrane and will replenish it with new proteins.

Question 27

Transport vesicle

Answer 27

A vesicle of the Golgi complex that brings new digestive enzymes to a lysosome, or will become a new lysosome.

Question 28

Somatic cell division

Answer 28

When a body cell undergoes nuclear division in order to produce a new body cell

(aka mitosis)

Question 29

Reproductive cell division

Answer 29

When a germ cell undergoes nuclear division, in order to produce a gamete.

(aka meiosis)

Question 30

Cytokinesis

Answer 30

Cytoplasmic division that occurs during mitosis or meiosis.