cell transport

Question 1

Why are cell membranes important?

Answer 1

Barrier between the cell and the environment
Controls what substances enter and leave the cell
They are partially permeable
Selectively allows substances to enter and leave via
diffusion, osmosis, and active transport.

Question 2

what is the structure of phospholipids

Answer 2

Arranged in a bilayer
Hydrophobic fatty acid tail
Hydrophilic phosphate head

Question 3

what is the function of phospholipids

Answer 3

Hydrophobic centre; water soluble substances (ions) cannot pass through but lipid soluble can (oxygen, water).

Question 4

what is the structure of cholesterol

Answer 4

Lipid molecule
Hydrophobic – attracts to phospholipid tails

Question 5

what is the function of cholesterol

Answer 5

Compacts phospholipid together, restricting their movement making the cell more rigid.
Prevent leakage of water and ions.

Question 6

what is the structure of channel proteins

Answer 6

Integral/transmembrane proteins
Water filled tubes

Question 7

what is the function of channel proteins

Answer 7

Allow water soluble ions and molecules to diffuse across the membrane (facilitated diffusion)

Question 8

what is the structure of Carrier proteins

Answer 8

Integral/transmembrane proteins

Question 9

what is the function of Carrier proteins

Answer 9

Actively transports specific substances across the membrane
Allows for facilitated diffusion of specific substances

Question 10

what is the structure of Glycolipids

Answer 10

Carbohydrates linked to lipids

Question 11

what is the function of Glycolipids

Answer 11

act as recognition sites for specific chemicals.
Assist with stability of the membrane

Question 12

what is the structure of Glycoproteins

Answer 12

Carbohydrates linked to (extrinsic) membrane proteins

Question 13

what is the function of glycoproteins

Answer 13

Act as recognition sites for specific chemicals.
Cell-cell recognition

Question 14

explain simple diffusion

Answer 14

Net movement of particles
From and area of high concentration to an area of low concentration (down a concentration gradient)
Passive process (does not require energy)

Question 15

explain facilitated diffusion

Answer 15

Net movement of large or charged particles
Use carrier or channel proteins
From and area of high concentration to an area of low concentration (down a concentration gradient)
Passive process (does not require energy)

Question 16

how do carrier proteins help facilitated diffusion

Answer 16

Molecule attaches to the carrier protein
Protein changes shape
Creates pathway release molecule into opposite side of membrane

Question 17

how do channel proteins help facilitated diffusion

Answer 17

Form pores in the membrane
Often used for charged particles
Water filled (hydrophilic)
Selective – only open in presence of specific ion

Question 18

what are factors affecting the rate of diffusion

Answer 18

Concentration gradient
Thickness of exchange surface
Surface area
(Temperature)

In addition for facilitated diffusion:
Number of carrier/channel proteins

Question 19

What is osmosis

Answer 19

Diffusion of water molecules from an area of high water potential to an area of low water potential through a partially permeable membrane

Question 20

What does water move through the cell membrane in, in osmosis

Answer 20

Aquaporins

Question 21

Higher water potential

Answer 21

Has the most water

Question 22

Solvent is

Answer 22

What something dissolves in

Question 23

Solute is

Answer 23

The thing that dissolves

Question 24

Solution is

Answer 24

Dissolved substance with a solvent

Question 25

What are the types of solutions

Answer 25

Isotonic Hypotonic Hypertonic

Question 26

What is an isotonic solution

Answer 26

Water potential is the same inside and outside the cell

Question 27

What is a Hypotonic solution

Answer 27

Water potential inside the cell is lower than outside

Question 28

What is a hypertonic solution

Answer 28

Water potential inside the cell is higher than outside

Question 29

What are the factors affecting the rate of osmosis

Answer 29

Water potential gradient Thickness of exchange surfaces Surface area Number of aquaporins

Question 30

what is active transport

Answer 30

Movement of molecules and ions, against a concentration gradient from an area of low concentration to an area of high concentration requiring energy from ATP and carrier proteins and co-transporters.

Question 31

what are cotransporters

Answer 31

carrier proteins which bind to 2 molecules, one is used to transport the other against the gradient or both can be transported into or out of a cell

Question 32

explain the process of active transport for a single molecule or ion

Answer 32

Molecule or ion binds to a specific receptor site on the transmembrane carrier protein. On the inside of the cell/organelle, ATP binds to the carrier protein. Carrier protein therefore changes shape and opens the opposite side. The molecule or ion is released to the other side of the membrane. The phosphate molecule (Pi) is then released from the carrier protein allowing the protein to return to its original shape, ready for process to repeat. During respiration, ATP is restored:

Question 33

what are factors affecting the rate of active transport

Answer 33

Speed of carrier proteins Number of carrier proteins Rate of respiration – impacts release of ATP

Question 34

what is the role of the ileum

Answer 34

to absorb molecules produced by digestion

Question 35

what are the 3 types of glucose absorption in the ileum

Answer 35

facilitated diffusion, active transport, co transport

Question 36

explain facilitated diffusion in the absorption of glucose

Answer 36

Epithelial cells line the ileum After digestion there is a high concentration of glucose in the lumen of ileum, Glucose molecules are absorbed by moving down the concentration gradient by facilitated diffusion into the epithelial cells that line the ileum, through carrier proteins. Glucose then moves into the blood stream, to be carried away

Question 37

explain active transport in the absorption of glucose

Answer 37

Using ATP hydrolysis the sodium potassium pump actively transports sodium ions out of the epithelial cells into the bloodstream. At the same time, the pump actively transports potassium ions from the bloodstream into the epithelial cells.

Question 38

Explain why facilitated diffusion alone is insufficient for glucose absorption in the ileum

Answer 38

The rule depends on the concentration gradient so as more glucose moves into epithelial cells the rate of facilitated diffusion decreases

Question 39

Explain co-transport inthe absorption of glucose in the ileum

Answer 39

Sodium ions ditture from the ileum to the epithelial cell vid the sodium glucose co-transporter protein, down the concentration gradient. Glucose is also forcefully pulled in against the concentration gradient, the energy for which comes from the energy store in the sodium ion

Question 40

How is efficient glucose absorption und transport maintained

Answer 40

Epithelial cells have many mitochondria to provide ATP for the Na-K pump. The cell membrane of epithelial cellshave many folds called micro villi which increase surface area for more carrier proteins/co-transporters. Steep concentration gradient in bloodstream is due to glucose being rapidly taken away