the plasma membrane

Question 1

what are the roles of the plasma membrane

Answer 1

• separates cell contents from the outside environment
• regulates the transport of nutrients into and out of the cell
• contains receptor sites
• recognition

Question 2

what are the roles of internal membranes

Answer 2

• separate cell components from cytoplasm
• hold the components of some metabolic pathways in place
• chemical reactions take place on membranes

Question 3

what is the fluid mosaic model

Answer 3

• molecules are not bonded together so their is some movement, but it is relatively stable because of the nature of phospholipids
• the phospholipids move around each other within a layer relative to one another
• proteins embedded between phospholipids vary in shape, size and pattern

Question 4

what are the components in a cell membrane

Answer 4

• phospholipid bilayer
• intrinsic and extrinsic proteins
• cholesterol
• glycoproteins and glycolipids

Question 5

what are extrinsic proteins

Answer 5

• they are on either side of the phospholipid bilayer
• provide structural support
• from recognition sites by identifying cells
• form receptor sites for hormone attachments

Question 6

what are intrinsic proteins

Answer 6

• extend across the bilayer
• provide structural support
• some are carrier proteins
• some are channel proteins

Question 7

what is diffusion

Answer 7

• ## a passive movement of molecules form a region of high concentration to an area of low concentration down a concentration gradient

Question 8

when does diffusion occur

Answer 8

• there is a concentration gradient
• molecules have kinetic energy
• no ATP energy is required
• no specific proteins are required

Question 9

what are the factors affecting diffusion

Answer 9

• temperature
• concentration
• surface area
• thickness of membrane
• diffusion distance
• size of molecule
• lipid solubility

Question 10

what is facilitated diffusion

Answer 10

• passive transfer of molecules or ions down a concentration gradient across a membrane by protein carrier molecules in the membrane

Question 11

what are hydrophilic channel proteins

Answer 11

• molecules with pores lined with polar groups
• each protein is specific and will only allow one type of ion through
• channels can be gated so they only open and close in specific circumstances

Question 12

what are carrier proteins

Answer 12

• allow specific large polar molecules to pass through the membrane
• a particular molecules will attach to the protein at its specific binding site and causes the protein to change shape, releasing the molecule through the membrane

Question 13

when does facilitated diffusion take place

Answer 13

• there is a concentration gradient
• molecules have kinetic energy and will be in a state if random movement
• no ATP energy is required
• carrier proteins and channel proteins are present

Question 14

what is active transport

Answer 14

• movement of ions and other molecules across the membrane using carrier proteins
• moving from a low concentration to a high concentration against the concentration gradient
• requires ATP energy

Question 15

when does active transport take place

Answer 15

• the movement is against the concentration gradient
• ATP energy is required
• cells are packed with mitochondria
• intrinsic carrier proteins are present
• if a respiratory inhibitor is present the rate of active transport will decrease

Question 16

what are the processes involving active transport

Answer 16

• protein synthesis
• muscle contraction
• nerve impulse transmission
• absorption of mineral salts by plant roots
• reabsorption of glucose by the kidneys

Question 17

what is co transport

Answer 17

• type of facilitated diffusion
• brings molecules and ions into cells together on the same transport molecule
• transports 2 substances in the same direction

Question 18

what is endocytosis

Answer 18

• bulk transport of substances into the cell
• membrane engulfs the material
• membrane fuses together
• vesicles are formed
• ATP required
• 2 types = phagocytosis, pinocytosis

Question 19

what is pinocytosis

Answer 19

• the entry of liquid by the same mechanism as phagocytosis but the vesicles are smaller

Question 20

what is exocytosis

Answer 20

• exit of substances from the cell after being transported through the cytoplasm in a vesicle
• digestive enzymes are often secreted this way

Question 21

what is phagocytosis

Answer 21

• the process where cells obtain solid materials that are too large to enter by diffusion or active transport
• a lysosome fuses with the vesicle formed, enzymes digest the solid material and the products are absorbed by the cytoplasm

Question 22

what is osmosis

Answer 22

• movement of water from an area of higher water potential to an area of lower water potential across a partially permeable membrane

Question 23

what is water potential

Answer 23

• the tendency for water molecules to enter or leave a solution by osmosis
• water can move more freely in a dilute solution compared to a more concentrated one

Question 24

what are hypertonic solutions

Answer 24

• have a lower water potential than the cytoplasm
• it contains less solutes

Question 25

what is an isotonic solution

Answer 25

- have the same water potential as the cytoplasm - it contains the same concentration of solutes

Question 26

what is a hypotonic solution

Answer 26

- has a higher water potential than the cytoplasm - contains more solutes