Diffusion + Osmosis + Passive and Active Transport + Endocytosis + Exocytosis

Question 1

What is passive transport?

Answer 1

The movement of materials in and out of a cell from an area of high concentration to an area of low concentration without any energy input. This moves with/along/down the gradient and basically naturally goes with the flow

Question 2

What are the two types of passive transport?

Answer 2

osmosis and diffusion

Question 3

What is simple diffusion?

Answer 3

(1)the movement of SOLUTE particles (2) from an area of high concentration to an area of low concentration (3) without energy input (4) until an equilibrium is reached

Question 4

What condition of the concentration gradient allows diffusion and osmosis to occur?

Answer 4

diffusion and osmosis can only occur along a concentration gradient where a solute is more concentrated in one area than another. So there has to be a high concentration place and a low concentration place

Question 5

What is osmosis?

Answer 5

(1) a type of diffusion (2) the net movement of SOLVENT (base) molecules across a semipermeable membrane (3) from a place of higher solvent concentration to low solvent concentration

Question 6

When is equilibrium reached in diffusion?

Answer 6

when there is equal movement of molecules in either direction. The particle STILL MOVES. It’s just that there is the same amount of molecules moving in as moving out.

Question 7

Describe simply how diffusion works with an example (non-scientifically)

Answer 7

if someone sprayed a burst of perfume (which is the solute in the solvent of air) in the back corner of a room, the people closest to the corner where the perfume was sprayed (and where it is the most concentrated) will smell it quickly. People at the front won’t smell anything yet. The perfume molecules will gradually move from the highest concentration in the back to the lowest concentration in the front. Basically, it will spread across the room until the concentration is even (EQUILIBRIUM). So, the perfume has diffused across the library with no energy

Question 8

What is movement along a concentration gradient?

Answer 8

movement from high concentration to low concentration

Question 9

Describe simply how movement along a concentration gradient works with an example (non-scientifically)

Answer 9

Molecules moving down or along a concentration gradient are like rocks rolling down a hill. They need no energy input to keep moving

Question 10

What factors can change the rate of diffusion?

Answer 10

• the difference in the concentration of substances
• mass of the molecule diffusing
• the temperature

Question 11

How does the temperature change the rate of diffusion?

Answer 11

more heat means more kinetic energy → more kinetic energy means faster movement of the particles

Question 12

How does the difference in the concentration of substances affect the diffusion rate?

Answer 12

a greater difference in the concentration of solvent and solute means the concentration gradient will be steeper and diffusion will occur faster. The greater the difference in concentration, the more rapid the diffusion. The closer the distribution of the material gets to equilibrium, the slower the rate of diffusion becomes

Question 13

What is active transport?

Answer 13

the movement of particles in and out of the cell from an area of low concentration to an area of high concentration with the energy needed to push through. This goes against the flow

Question 14

Does passive transport go along/down or against/up the concentration gradient?

Answer 14

along the concentration gradient

Question 15

Does active transport go along/down or against/up the concentration gradient?

Answer 15

against

Question 16

What are the two types of active transport?

Answer 16

exocytosis and endocytosis

Question 17

What solvent is commonly used in osmosis?

Answer 17

water as the solvent

Question 18

What is osmosis (in terms of water)?

Answer 18

the process through which water moves through a cell membrane

Question 19

What type of particles can move through a cell membrane using diffusion?

Answer 19

small and uncharged or very minimally charged molecules

Question 20

Why do charged molecules of any size struggle to passively cross a cell membrane?

Answer 20

The hydrophilic heads of the cell membrane (fluid mosaic) are charged (negatively) and the middle hydrophobic layer of tails is uncharged. Like oil and water, charged molecules are repelled by uncharged molecules. So a charged molecule can pass through the hydrophilic heads but are stopped when it tries to push through the uncharged tail area in the middle

Question 21

Why do large polar molecules struggle to passively cross a cell membrane?

Answer 21

Polar molecules have one slightly positive side and one slightly negative side and are hydrophilic. The hydrophobic inside tails are uncharged (non-polar) and repel water and charged molecules. Because of their charge, polar molecules can get through the hydrophilic heads but are repelled by the hydrophobic, non-polar heads inside tails. Small polar molecules may get through if their charge is not too significant.

Question 22

What two substances will never reach equilibrium with diffusion in the body and why?

Answer 22

Oxygen and carbon dioxide, because cells rapidly use up oxygen during metabolism so there will usually be less oxygen inside the cells than outside. Carbon dioxide is produced in the metabolism process, so the carbon dioxide concentrations will have more inside the cells

Question 23

What are some substances that can diffuse passively through the cell membrane and why?

Answer 23

Carbon dioxide and oxygen because they are both small with no charge and will not interfere with the non-polar hydrophobic tails. Carbon dioxide also has a higher concentration inside and diffuses outside while oxygen has a higher concentration outside and diffuses inside

Question 24

What are some substances that would have trouble getting through the cell membrane and why?

Answer 24

charged molecules like potassium ions, sodium ions and chloride ions or large molecules like glucose and amino acids. Because both are positively charged, they would be attracted to the negative hydrophilic heads, and then be too attached to continue moving through the hydrophilic tails that have no charge to entice them with .

Question 25

How does water passively move through the cell membrane?

Answer 25

First, because of the hydrophilic heads that attract water molecules. Also because water molecules are small and can diffuse slowly through

Question 26

What should potentially stop water from moving through the cell membrane but doesn’t;t?

Answer 26

The hydrogen in water is positively charged. However, the charge is not strong enough that it will completely stop them. Not all, but a lot of them will passively diffuse through.

Question 27

What is facilitated diffusion?

Answer 27

a process that uses membrane proteins to transport polar or charged molecules through the hydrophobic tail areas by “covering” their charge and “protecting” them from being repelled.

Question 28

What are the two forms of membrane proteins?

Answer 28

membrane proteins can be either channel proteins or carrier proteins

Question 29

Is facilitated diffusion along or against the gradient?

Answer 29

It is still along the gradient. The carrier proteins will always pick up and deposit molecules from a high concentration area to a low concentration area

Question 30

How do carrier proteins help with facilitated diffusion?

Answer 30

They pick up the particles on one side of the cell membrane, change shape to hold them in and release the substance on the other side

Question 31

What is an example of a molecule that would need a carrier protein?

Answer 31

glucose

Question 32

How do channel proteins help with facilitated diffusion?

Answer 32

Channel proteins work like tunnels, opening to allow the molecules to move through and closing after

Question 33

Why can water not diffuse directly through the lipid bilayer?

Answer 33

Because water is not lipid soluble

Question 34

How does water typically move through the cell membrane?

Answer 34

through special tiny channel proteins called aquaporins (water pores)

Question 35

What is the name of the channel proteins water uses to pass through the cell membrane in osmosis?

Answer 35

aquaporins or water pores

Question 36

What happens to the cell during osmosis if the water concentration is higher outside?

Answer 36

water will move by osmosis into the cell and the cell may swell up

Question 37

What happens to the cell during osmosis if the water concentration is higher inside?

Answer 37

water will move out of the cell by osmosis and the cell may shrink

Question 38

What is osmotic pressure?

Answer 38

The pressure created by water moving across the semipermeable membrane due to osmosis

Question 39

What increases osmotic pressure?

Answer 39

The more water that moves across the membrane, the higher the osmotic pressure

Question 40

What does isotonic mean?

Answer 40

the same concentration. When the fluids inside and outside a cell are of equal solute concentration, the external solution is isotonic to the inside solution

Question 41

What does the prefix “iso” mean?

Answer 41

same

Question 42

What does hypotonic mean?

Answer 42

when cells have a higher solute concentration inside and a lower solute concentration outside

Question 43

How is water movement when the internal and external cell fluids are isotonic?

Answer 43

water moves inside and outside equally because the solute concentration is perfect

Question 44

How is water movement when the external cell fluids are hypotonic to the internal cell fluids?

Answer 44

hypo means lower → so the outside cell fluids are lower in solute concentration → more water will be moving from the outside to the inside of the cell, to dilute the higher outside solute concentration and reach balanced, isotonic state

Question 45

What does the prefix hypo mean?

Answer 45

lower

Question 46

What does hypertonic mean?

Answer 46

when cells have a lower solute concentration inside and a higher solute concentration outside

Question 47

What does the prefix hyper mean?

Answer 47

higher

Question 48

How is water movement when the external cell fluids are hypertonic to the internal cell fluids?

Answer 48

hyper means higher → the external cell fluids are higher in concentration → more water will be moving from the inside of cell to the outside to dilute the higher outside concentration and reach a balanced, isotonic state

Question 49

Will water move (1) from hypotonic to hypertonic or (2) from hypertonic to hypotonic?

Question 50

What are the 2 main rules for the direction of water movement in osmosis?

Answer 50

(1) Water will always move more from a place with a low concentration of solute to a place with a high concentration to balance out the concentrations
(2) Water will still move in BOTH directions, just MORE towards the place of high concentration

Question 51

Equilibrium is reached for a hypertonic, hypotonic or isotonic solution?

Answer 51

isotonic

Question 52

Is osmosis passive or active transport?

Answer 52

osmosis requires no energy input, so it is passive

Question 53

What is the issue of a cell’s inside fluids being hypotonic for a unicellular eukaryotic organism?

Answer 53

because unicellular eukaryotes are surrounded only by a cell membrane if a cell’s inside fluid is hypotonic to the outside fluid, water will continue to flow in until the concentration is equal. However, too much water flowing in can cause the cell to swell and eventually burst.

Question 54

How do cells in animals prevent bursting when internal cell fluids are isotonic?

Answer 54

Animal cells are not directly exposed to the external environment → Their external cell fluid is isotonic → so water can diffuse equally in both direction

Question 55

Why do animal cells need to have isotonic internal cell fluids?

Answer 55

to coordinate biochemical reactions

Question 56

What is turgor pressure?

Answer 56

internal pressure