Cell Transport

Question 1

Why are cells small?

Answer 1

Small cells with larger SA:VOL ratios have less volume and MORE surface area so they can exchange the materials they need faster

Large cells with smaller SA:VOL ratios have MORE volume and LESS surface area so they exchange materials slower

this is why cells are small

Question 2

Why is the cell membrane a fluid mosaic?

Answer 2

Because the proteins and phospholipids can move laterally in the membrane due to hydrophilic/hydrophobic properties

Question 3

Simple diffusion:

Answer 3

Passive transport, moves with the concentration gradient and does not require anything to help it

Question 4

Facilitated diffusion:

Answer 4

Passive transport, moves with concentration gradient but it is helped by a transport protein

Question 5

Concentration gradient:

Answer 5

High —-> Low concentration

Question 6

Major functions of cell membrane:

Answer 6

cell membranes decide what passes through it and moves into the cell and what cannot, decides what gets to leave the cell

• signaling abilities

Question 7

Phospholipid structure role in cell membrane

Answer 7

two layers of lipids with a hydrophilic head and hydrophobic tail

tails face inwards towards each other this makes up phospholipid bilayer

phospholipid bilayer is where the cells have to go through

Question 8

Proteins role in cell membrane

Answer 8

• Allow the cell to be recognized by other cells (receptor protein)
  -transport materials across phospholipid bilayer (Transport protein)

Question 9

Cholesterol role in cell membrane

Answer 9

• adds to membrane structure (fluidness)
• helps regulate movement of molecules across membrane

Question 10

What can and cannot pass freely through the cell membrane?

Answer 10

Water, carbon dioxide, and oxygen can pass freely

Question 11

What is diffusion?

Answer 11

hydrophobic molecules that are small can diffuse through the phospholipid bilayer without any help

Question 12

What is osmosis?

Answer 12

The movement of water through a semipermeable membrane.
Water molecules can pass freely through the cell membrane.

• they move from high water conc. to low water conc.
• or the water moves from low to high concentrations of solutes

Question 13

what is a solute?

Answer 13

substances like salt or sugar that are dissolved in a solvent

Question 14

Hypertonic:

Answer 14

Higher solute concentration is hypertonic

Question 15

Hypotonic

Answer 15

Lower solute concentration is hypotonic

Question 16

Brownian Motion

Answer 16

The random movement of microscopic particles suspended in a liquid or gas, caused by collisions with molecules of the surrounding medium

Question 17

Equilibrium

Answer 17

When concentration of solutes/solvents is equal on both sides of the cell membrane

Question 18

Active Transport:

Answer 18

Requires energy (ATP)
Allows molecules to move against the concentration gradient (low to high instead of high to low)

Question 19

Endocytosis

Answer 19

active transport
- large amounts of molecules or larger molecules fuse with the cell membrane and go into a vesicle in order to pass through the cell membrane

Question 20

Exocytosis

Answer 20

Active transport
when the vesicle containing wastes moves the wastes out of the cell

Question 21

what do cells do in an hypertonic solution?

Answer 21

The cell will shrivel and die because a the water in the cell moves from high to low concentration of water.

Question 22

What do cells do in an hypotonic

Answer 22

the cell will swell because the water in the solution is moving into the cell because it is moving from a high to low concentration of water

Question 23

What happens to cells in isotonic

Answer 23

they stay the same

Question 24

What happens in a negative feedback loop?

Answer 24

The feedback counteracts the stimulus (Ex: the stimulus is high blood sugar and the feedback causes the blood sugar to get lower)

Question 25

What happens in a positive feedback loop?

Answer 25

The feedback enhances/amplifies and/or continues going in the direction that the stimulus was going
Ex:
When the baby’s head presses against the cervix and that triggers a positive feedback loop with oxytocin and etc.