CELL MEMBRANES AND TRANSPORT

Question 1

what are the four components that make a cell membrane?

Answer 1

lipids, cholesterol, proteins and carbohydrates

Question 2

what are the functions of a cell membrane?

Answer 2

controls what enters and exits the cell
keeps cell components inside the cell
acts as a sit for biochemical reactions

Question 3

what is the structure of a phospholipid?

Answer 3

made up of a phosphate group and two fatty acid chains: hydrophilic head and hydrophobic tail

Question 4

what molecules can pass through the phospholipid bilayer?

Answer 4

small, non polar molecules

Question 5

what is the structure of a cholesterol molecule?

Answer 5

hydrophilic head and hydrophobic tail

Question 6

what is the role of cholesterol in the cell membrane?

Answer 6

it fits between phospholipid molecules and regulates the fluidity of the membrane and keeps it stable

Question 7

what are the two types of proteins found in the cell membrane?

Answer 7

integral (intrinsic) and peripheral (extrinsic)

Question 8

what are the roles of proteins in the cell membrane?

Answer 8

transport proteins move substances that are unable to pass through the phospholipid bilayer such as ions

peripheral proteins act as receptors for cell recognition

act as antigens for cell to cell recognition and signalling

Question 9

what do carbohydrates for on the cell membrane?

Answer 9

glycoproteins when they attach to a protein

glycolipids when they attach to a lipid

Question 10

what are the roles of glycoproteins and glycolipids?

Answer 10

some act as receptors

used for cell recognition and cell signalling

Question 11

what is meant by the fluid mosaic model?

Answer 11

the term fluid relates to the phospholipids in the membrane constantly moving. the term mosaic describes the top view of the cell wall as a mosaic from the scattered proteins, cholesterol, phospholipids and carbs

Question 12

how thick in the cell wall?

Answer 12

7nm

Question 13

how does temperature affect the cell membrane’s fluidity?

Answer 13

when temperature increases, fluidity increases
when temperature decreases, fluidity decreases

when temperature increases, cholesterol will pull the phospholipids together, which decreases the fluidity

when temperature decreases, cholesterol will push the phospholipids making more spaces between them, which increases the fluidity

Question 14

what is diffusion?

Answer 14

the net movement of particles from a region of high concentration to a region of low concentration down a concentration gradient

Question 15

what type of process is diffusion and why?

Answer 15

passive as it doesn’t need energy

Question 16

how does temperature affect the rate of diffusion?

Answer 16

as temperature rises particles gain more kinetic energy and move faster causing diffusion to take place faster

Question 17

how does surface area affect the rate of diffusion?

Answer 17

the more surface area of the membrane the more diffusion can occur

Question 18

how does the concentration gradient affect the rate of diffusion?

Answer 18

the steeper the concentration gradient the faster the net movement of diffusion

Question 19

what is facilitated diffusion?

Answer 19

the passive diffusion of large polar molecules across the membrane through a protein channel

Question 20

what is active transport?

Answer 20

the movement of molecules across the cell membrane against the concentration gradient using ATP

Question 21

what proteins does active transport use?

Answer 21

carrier protein

Question 22

what is endocytosis?

Answer 22

engulfing of materials by the plasma membrane. this includes phagocytosis and pinocytosis

Question 23

what is exocytosis?

Answer 23

the transport of materials out of the cell by the fusion of vesicles with the cell membrane

Question 24

what is osmosis?

Answer 24

the net movement of water molecules from an area of high water potential to an area of low water potential through a partially permeable membrane

Question 25

what does hypotonic mean?

Answer 25

when there is more water potential outside the cell than inside the cell so the net movement of water goes inside the cell

plant cells are turgid and animal cells are lysed

Question 26

what does isotonic mean?

Answer 26

when there is an equal amount of water potential inside and outside the cell and the net movement is the same

plant cells are flaccid and animal cells are normal

Question 27

what does hypertonic mean?

Answer 27

when there is more water potential inside the cell than outside the cell so the net movement of water goes outside the cell

plant cells are plasmolyzed and animal cells are shriveled