Success In Biology

Question 1

Endosymbiotic Theory

Answer 1

Organelles of eukaryotes evolved through symbiosis of prokaryotes.
Similarities between mitochondria, chloroplast and prokaryotic cells.

Question 2

Plasma membranes are amphipathic

Answer 2

Posses both hydrophilic (water-dissolving, polar) and hydrophobic (water-resistant, non-polar) regions.

Question 3

Peripheral Proteins

Answer 3

• more of these than integral proteins.
• surface proteins.
• glycoproteins.

Question 4

Integral Proteins

Answer 4

1. Completely embedded
2. Transmembrane
   a. transport proteins (i.e protein channels)
   b. some glycoproteins
   c. membrane receptors
3. When cross lipid bilateral takes alpha helix shape.

Question 5

Glycoproteins + Glycolipids

Answer 5

1. Found on extra-cellular surface of membranes.
2. Proteins and lipids have short carbohydrate chains extending out.
3. Form OH bonds with water surrounding cells, reinforcing cell structure.

Question 6

Membrane receptors (integral proteins)

Answer 6

1. Bind to molecules outside of cell and transfer messages from outside to inside cell.
   a. Ligand-gated ion channel receptors
   b. Enzyme-coupled receptors
   c. G-protein coupled receptors.

Question 7

Lipid-Raft Theory

Answer 7

Lipid rafts are dense regions of the plasma membrane that are heavy in cholesterols and serve as protein signaling platforms.

Question 8

Osmosis and Aquaporins

Answer 8

Osmosis is movement of water molecules across a selectively permeable membrane into a compartment containing solute unable to cross that membrane
a. Aquaporins: transport proteins allowing water in and out ( not gated; open/close).

Question 9

Osmolarity vs Osmolality vs Tonicity (Terms describing solute concentrations)

Answer 9

Osmolarity: solute concentration per volume of solvent.
Osmolality: solute concentration per mass of solvent.
Tonicity: Ability of solution surrounding a cell to cause the cell to gain or lose water.

Question 10

Isotonic (osmosis)

Answer 10

Concentration of solute is same inside and outside of cell

Question 11

Hypertonic (osmosis)

Answer 11

Concentration of solute is higher outside the cell than inside (cell shrivels)

Question 12

Hypotonic (osmosis)

Answer 12

Concentration of solute is higher inside the cell than outside (cell bloats)

Question 13

Diffusion

Answer 13

Movement of molecules or ions in liquid or gas from areas of high concentration to lower concentration.
a. Occurs down a concentration gradient.
b. Cell membrane permeable to only that substance.
C. O2 diffuses in and CO2 out of cell.

Question 14

Facilitated Diffusion

Answer 14

Substances unable to pass through lipid bilayer need help from membrane proteins.

a. ion channels
b. Carrier molecules: for molecules not lipid-soluble and too big e.g glucose
c. Insulin promotes facilitated diffusion of glucose.
d. Specific because carrier molecule only binds to certain solute.

Question 15

Filtration

Answer 15

Forces molecules through membranes by exerting pressure (hydrostatic).
a. Blood pressure generated by heart action

Question 16

Active Transport

Answer 16

Moves from regions of lower concentrations to higher concentrations through membrane.

a. Uses carrier molecules and ATP
b. Transported are: sugars, amino acids, and ions.

Question 17

Endocytosis + Exocytosis

Answer 17

Processes using cellular energy to move substances in/out of cell without crossing cell membrane.

a. Endocytosis: particles too big to enter via diffusion or active transport are conveyed in a vesicle formed from a portion of the membrane. (Types: pinocytosis, phagocytosis, receptor-mediated endocytosis).
b. Exocytosis: secretes substance stored in vesicle from cell. e.g nerve cells secreting neurotransmitters.

Question 18

Pinocytosis (Endocytosis)

Answer 18

1. “Cell drinking.” Cells take in tiny droplets of liquids from surroundings.
2. Takes in water and substances dissolved in it too large to enter.
3. Vesicle forms from portion of cell membrane

Question 19

Phagocytosis (Endocytosis)

Answer 19

1. “Cell eating.” Cell takes in solids.

2. Portion of cell membrane projects outward once solid particle comes into contact and draws inside.

Question 20

Receptor-mediated Endocytosis (Endocytosis)

Answer 20

1. Moves very specific kinds of particles into cell.
2. Protein molecules extending to outer surface of cell membrane act as receptor that specific molecules bind to (ligand)
3. Cholesterol enters this way.

Question 21

Passive Transport

Answer 21

Molecules move in and out of cell according to concentration gradient.
a. Moves by Kinetic energy and NO ATP REQUIRED.