Class 4 - Cell Form & Function pt. 2

Question 1

Passive mechanisms of membrane transport (3)

Answer 1

1. Filtration - Particles driven by physical pressure (e.g. filtration pores in capillary walls).
2. Simple diffusion - Net movement of particles from high to low concentration
3. Osmosis - Net flow of water thru selectively permeable membrane (high water/low solute to low water/high solute). Enhanced by aquaporins in bilayer

Question 2

Factors which increase diffusion rate (5)

Answer 2

1. Higher temperature
2. Lighter molecular weight
3. Steeper gradient (more difference)
4. Greater membrane surface area
5. Greater membrane permeability

Question 3

Osmotic pressure, hydrostatic pressure, reverse osmosis

Answer 3

Osmotic pressure - Hydrostatic pressure required to stop osmosis. Increases as amount of non-permeating solute rises

Hydrostatic pressure - Fluid pressure on membrane

Reverse osmosis - Process of applying mechanical pressure to override osmotic pressure (e.g water purification).

Question 4

Osmolarity and tonicity

Answer 4

Osmolarity - Osmotic concentration; quantity of non-permeating solutes per liter of solution

Tonicity - Ability of surrounding solution to affect fluid volume and pressure in a cell. Depends on concentration of np solutes

Question 5

Tonicity: Hypotonic, hypertonic, and isotonic solutions

Answer 5

Hypotonic - Causes cell to absorb. Lower np solute concentration than ICF

Hypertonic - Causes cell to lose water. Higher np solute concentration than ICF

Isotonic - Causes no change in cell volume. Np solute concentation equal to ICF

Question 6

Carrier-mediated transport

Answer 6

Protein carriers in membrane carry solutes in/out of cell/organelle

Exhibit specificity in targets.

Exhibit saturation once transport maximum is reached

Question 7

Three types of carrier proteins

Answer 7

1. Uniport - Moves one solute at a time (Ca+ pump)
2. Symport - Moves 2+ solutes simultaneously in same direction (Na+ glucose pump).
3. Antiport - Moves 2+ solites in opposite directions

Question 8

Three mechanisms of carrier-mediated transport

Answer 8

1. Facilitated diffusion - moves solute down concentration gradient, no ATP
2. Primary active - moves solute against gradient, requires ATP (Na+ K+ pump)
3. Secondary active - moves solute through membrane using ATP indirectly

Question 9

Vesicular transport

Answer 9

Moves large particles, fluid droplets, or numerous molecules at once thru membrane in vesicles.

Question 10

3 forms of Endocytosis

Answer 10

1. Phagocytosis - Engulfs and destroys large particles. Pseudopod surrounds object, forming phagosome which fuses with lysosome.
2. Pinocytosis - Take in droplets of ECF containing useful molecules into cytoplasm.
3. Receptor-mediated Endocytosis - Particles bind to specific receptors on plasma membrane, form clathrin-coated vesicles

Question 11

Cytosol and cytoskeleton

Answer 11

Cytosol - liquid portion of the cell, contains enzymes, amino acids, ATP, electrolytes, dissolved gases, and metabolic waste

Cytoskeleton - Network of protein filaments. Provides support, determines shape, organizes contents, and directs movement within cell

Question 12

Nucleus

Answer 12

Largest organelle, double membrane (nuclear envelope). Contains genetic material. Most cells have one but some are multinuclear or anuclear

Has nuclear pores, nucleoplasm, nuclear lamina

Question 13

Endoplasmic reticulum

Answer 13

Interconnected cisternae; continuous with nuclear envelope.

Rough ER - Produces phospholipids and proteins of cell membranes; synthesizes proteins packaged in Golgi or secreted

Smooth ER - Synthesizes steroids/other lipids. Detoxifies alcohol. Calcium storage

Question 14

Ribosomes

Answer 14

Not membrane bound. Carry out protein synthesis. Found in nucleoli, cytosol, rough ER, and nuclear envelope

Free ribosomes make proteins for inside cell
Bound ribosomes make for outside.

Question 15

Golgi complex

Answer 15

System of cisterns that synthesize carbs and modify/sort (add sugar to) newly synthesized proteins from ER.

Vesicles either become lysosomes, fuse with plasma membrane, or become secretory vesicles stored for later release

Question 16

Lysosomes + autophagy, autolysis

Answer 16

Membrane bound; full of enzymes. Digest substances.

Autophagy - digestion of cell’s surplus organelles

Autolysis - digestion of cell by itself (cell suicide)

Question 17

Peroxisomes

Answer 17

Produced by ER and contains enzymes. Use molecular oxygen to oxidize organic molecules.

Produce hydrogen peroxide which catalase breaks down to H2O and O2.

Neutralizes free radicals, detoxifies alcohol. Breaks down fatty acids into acetyl groups for mitochondrial ATP synthesis.

Question 18

Proteasome

Answer 18

Hollow, cylindrical organelles that dispose of proteins. Contain enzymes.

Question 19

Mitochondria

Answer 19

Double membrane, inner folds called cristae. Matrix has ribosomes and enzymes for ATP synthesis.

Question 20

Centriole

Answer 20

Not membrane bound. Assembly of microtubules. Two lie perpendicular together within the centrosome.

Play important role in cell division. Form the basal bodies of cilia and flagella

Question 21

Inclusions

Answer 21

Storage products or foreign matter in cytoplasm. Never enclosed in a membrane; not essential for cell survival