Cell Membrane, Diffusion, Osmosis

Question 0

Cell membrane functions

Answer 0

• separates internal from external environment
• regulates movement of nucleus into & out of cell
• cell-to-cell recognition
• binding site for molecules
• sets up enzymatic sequence

Question 1

Fluid Mosaic Model meaning

Answer 1

• fluid: fatty acid tails of phospholipids that make the inner membrane like a light oil
• mosaic: the mosaic-like appearance of proteins scattered outside or within the membrane

Question 2

Cell membrane consists of

Answer 2

• phospholipid bilayer with embedded proteins (fluid mosaic model)
• hydrophilic polar heads face towards exterior and interior of the cell
• hydrophobic non-polar fatty acid tails face each other in the middle

Question 3

Cholesterol function

Answer 3

• stiffens & strengthens membrane

- helps regulate fluidity of membrane

Question 4

Types of proteins

Answer 4

• can be peripheral (attached to outside) or integral (embedded in membrane) proteins
• transport proteins
• receptor proteins
• enzymatic proteins
• cell recognition proteins

Question 5

Transport Proteins

Answer 5

• channel proteins: create a pore that allows a particular molecule or ion to cross the membrane
• carrier protein: each type of protein only interacts with one specific molecule to allow it into the cell
  Ex. Glucose & amino acids brought in this way

Question 6

Receptor Proteins

Answer 6

• bind to hormones
• change protein shape
• trigger cellular responses

Question 7

Enzymatic Proteins

Answer 7

• catalyze (speed up) metabolic reactions

Question 8

Cell Recognition Proteins

Answer 8

• have glycoproteins that are unique to each individual

Question 9

Attached carbohydrate chains

Answer 9

• named for their attachment to the membrane
• glycolipids: attach to phospholipids
• glycoproteins: attach to proteins, involved in cell recognition, unique to individuals

Question 10

Glycocalyx

Answer 10

General term used for glycolipid & glycoprotein layer around cell

Question 11

Membrane

Answer 11

• selectively/differentially permeable (can select what passes though it)
• small, uncharged H2O molecules can pass through, but big or charged molecules need help across

Question 12

Passive Transport

Answer 12

• one way of passing through membrane
• no ATP
• ex. Facilitated diffusion, osmosis

Question 13

Active Transport

Answer 13

• one way of passing through the membrane
• needs ATP
• ex: ion pumps, co-transport, endocytosis

Question 14

Diffusion

Answer 14

• Molecules move from high [ ] to low [ ] (with the concentration gradient)
• particles move randomly but spread out evenly to achieve equilibrium
• molecules that enter/leave through diffusion are small and/or lipid soluble: oxygen, CO2, alcohol, small lipids

Question 15

Lungs and diffusion

Answer 15

• lungs rely on diffusion to add oxygen to the blood and remove CO2
• ie. oxygen diffuses along concentration gradient in the blood

Question 16

Osmosis

Answer 16

• diffusion of only water across a selectively permeable membrane

Question 17

Solution

Answer 17

Contains a solute (solid dissolved in water) and solvent (liquid)

Question 18

3 categories of solutions

Answer 18

• isotonic
• hypotonic
• hypertonic

Question 19

Isotonic solutions

Answer 19

• iso: equal
• solute [ ] equal inside & outside cell
• no net movement of water in or out
• ex. NaCl solution isotonic to blood

Question 20

Hypotonic Solutions

Answer 20

• hype: low/less
• solute concentration around the cell is less than the cell’s cytoplasm
• water enters cell to balance concentrations (puffy cell-hypotonic)

Question 21

Cell reactions in hypotonic solutions

Answer 21

• Cytolysis: When animal cells burst (occurs in animal cells but not plant cells due to rigid cell wall)
• plant cells increase turgar pressure

Question 22

Hypertonic solutions

Answer 22

• hyper: high/greater
• fluid surrounding cell has higher concentration than cell’s cytoplasm
• water leaves the cell (bumpy cell- hypertonic)

Question 23

Reactions of cells in hypertonic solutions

Answer 23

• animal cell shrivels “crenation”

- plant cells go through “plasmolysis”

Question 24

Osmoregulation

Answer 24

Animals living on water face an osmotic difference between their cells & surrounding water

Question 25

Freshwater osmoregulation

Answer 25

• salt in body > salt in water
• animals:
  
  • excrete large amounts of water in urine
  • contractile vacuoles in single-cell organisms expel water

Question 27

Saltwater osmoregulation

Answer 27

• salt in body less than salt in water…water leaves cells
• animals:
  
  • make their body surfaces less permeable
  • pump salts out of blood & back into sea water
  • produce very small amount of urine to get rid of metabolic waste (source of water loss)
  • drink to replace lost water
  • get rid of excess ions by active transport from body fluids back into water