✅4: cell transport mechanisms

Question 1

why do cells need a transport system?

Answer 1

they require chemicals and glucose and oxygen for cellular respiration. also need to get rid of waste products such as carbon dioxide etc. cells also have to transport raw materials into the cell.

Question 2

what does the cell surface membrane act as?

Answer 2

a gatekeeper to the cell, controlling the transport of materials into and out of the cell.

Question 3

what organelles also have membranes?

Answer 3

golgi apparatus and endoplasmic reticulum. they are both membrane bound structures that move substances about inside the cell.

Question 4

what are glycoproteins?

Answer 4

act as antigens, cell recognition or as receptors for hormones or neurotransmitter.

Question 5

what do the peripheral proteins do?

Answer 5

may be enzymes, can be involved in regulating transport etc by cell signalling.

Question 6

what do integral proteins do?

Answer 6

main transport system of the membrane, forming either permanent pores in hydrophilic channles, or other transport mechanisms such as carrier proteins or active pumps involving enzymes.

Question 7

what does the membrane bilayer do?

Answer 7

made out of phospholipids and other polar lipids. have hydrohplic tails and hydrophilic heads therefore point outwards.

Question 8

when does passive transport occur?

Answer 8

as a result of pressure, concentration or electrochemical gradients and involves no energy from the cell.

Question 9

when does active transport take place

Answer 9

moving substances in our out of the cell. uses adenosine triphosphate ATP, produced during cellular respiration.

Question 10

what is diffusion?

Answer 10

the movement of particles from an area of high concentration to an area of low concentration. as a result of random movements. cell membranes are no barrier to diffusion of small particles such as gases oxygen and carbon dioxide.

Question 11

what is facilitated diffusion?

Answer 11

diffusion which takes place through carrier proteins or protein channels. the protein lined pores of the cell membrane make facilitated diffusion possible

Question 12

what is osmosis?

Answer 12

involves the movement of solvent molecules, usually water, down a concentration gradient, through a partially permeable membrane.

Question 13

what is endocytosis?

Answer 13

the movement of large molecules into cells through vesicle formation.

Question 14

what is exocytosis?

Answer 14

movement of large molecules out cells trough vesicle formation.

Question 15

why do the properties of membrane and particles important?

Answer 15

the presence or absence of a charge can affect. small molecules can pass easily, where as large cannot. if a charge is on the molecule, it will need specific carriers to make it through the membrane.

Question 16

how does diffusion happen?

Answer 16

move down concentration gradient. due to the random motions of molecules due to the energy they have will depend on the temperature. if large molecules tightly packed together, random movement will continue unity they reach a uniformed distribution. molecules don’t stop moving until they have reached this.

Question 17

how does facilitated diffusion happen?

Answer 17

substances with a strong charge or large molecules cannot pass through with simple diffusion. they can, however, by using proteins in the membrane that allow only specific molecules through passively down their own concentration gradient.

Question 18

what are gated channels?

Answer 18

when a specific molecule is present, or there is an electrical charge, gated channels allow them to pass.

Question 19

how to the carrier proteins work?

Answer 19

found on the outside of the membrane when a substance is to be moved into to cell, and on the inside for transport out of the cell. they rotate through the membrane to the other side.

Question 20

what is osmotic concentration?

Answer 20

measure of the concentration of the solutes in a solution that have an osmotic effect.

Question 21

why is osmosis important?

Answer 21

if not controlled, the cells would swell and burst. turgid or flaccid.

Question 22

how do you model osmosis working?

Answer 22

sucrose in a solution with a partially permeable membrane and pure water. 30 mins later, the sucrose would’ve entered the pure water.
can be shown by carrying out benedicts test for non-reducing sugars on the solution.

Question 23

what is an isotonic solution?

Answer 23

the osmotic concentration of the solutes in the solution is the same as that in the cells.

Question 24

what is a hypotonic solution

Answer 24

the osmotic concentration of the solutes is lower than that in the cytoplasm of the cells.

Question 25

what is hypertonic solution?

Answer 25

osmotic concentration of solutes in the solution is higher than that in the cytoplasm.

Question 26

what happens in osmosis in animal cells?

Answer 26

need to be carefully controlled, where the net movement of water in or out needs to be kept minimum. they are like fragile balloons filled with jelly. too much, cell will burst. too little, cells shrivel and die cytoplasm loses its internal structure and chemical reactions stop working.

Question 27

what happens with osmosis in plant cells?

Answer 27

cells are inside a cell wall, therefore more protected.

Question 28

what happens to a plant cell if the solution is hypotonic?

Answer 28

water will enter by osmosis, but not indefinitely. as cytoplasm swells and presses on the cell wall, it generates hydrostatic pressure. pressure potential is set up. when the osmotic force movign water into the plant cells is balanced by pressure potential, the plant is rigid, turgor.

Question 29

what is pressure potential?

Answer 29

inward pressure of the cell wall on the cytoplasm increases until it cancels out the tendency for water molecules to move in.

Question 30

what happens to plant cell if the solution is hypertonic?

Answer 30

water moves out of the cell by osmosis and turgor is lost. the cell membrane begins to full away from the cell wall as the protoplasm shrinks. called incipient plasmolysis.

Question 31

what is plasmolysis?

Answer 31

situation where a plant cell is placed in hypertonic solution when so much water leaves the cell y osmosis that the vacuole is reduced and the protoplasm is concentrated and shrinks away form the cell walls.

Question 32

what is water potential?

Answer 32

a measure of the potential for water to move out of a solution by osmosis. pure water has the highest water potential due to any substance moving into it form a partial permeable membrane. it is given the value 0, therefore all other is negative.

Question 33

what is the alternative definition of osmosis with water potential considered?

Answer 33

the net movement of water molecules from an area of higher water potential to an area of lower water potential though a partially permeable membrane.

Question 34

what is turgor pressure?

Answer 34

measure of the inwards pressure exerted by the plant cell wall on the protoplasm of the cell as the cell contents expands and press outwards, a force which opposes the entry of ate by osmosis.

Question 35

what is osmotic pressure?

Answer 35

measure of the potential of a solution to cause water to move into the cell across a partially permeable membrane as a result of dissolved solutes.

Question 36

how do you calculate the water potential of a cell?

Answer 36

turgor pressure + osmotic pressure

always positive ) (always negative

Question 37

what does active transport involve?

Answer 37

carrier proteins, which often span the whole membrane.

Question 38

what energy is needed for active transport?

Answer 38

ATP. ATP is made during cellular respiration. involves enzyme ATPhase, which catalyses the hydrolysis of ATP.

Question 39

what is meant by active transport is a one way system?

Answer 39

the carriers will not transport a substance back through the membrane.

Question 40

how fast is active transport?

Answer 40

can move substances in faster than they can move out by diffusion.

Question 41

what is active transport usually linked with?

Answer 41

with another particle. eg pumps with ions etc.

Question 42

what pump is needed for the nervous system?

Answer 42

Na ion pumps. each nerve impulse depends on an influx of sodium ions through the axon membrane.

Question 43

what is the evidence for there being active transport?

Answer 43

only takes place in living things. the rate of active transport depends on temperature and oxygen concentration. these affect the rate of reaction. many cells are known to carry out lots of active transport contain lots of mitochondria.
poison that stops respiration also stops active transport.

Question 44

how does endocytosis work?

Answer 44

materials are surrounded and taken up into membrane bound vesicles, in endocytosis.
eg ingestion of bacteria during phagocytosis- cell eating.

Question 45

what is pinocytosis?

Answer 45

microscopic level when tiny amounts of surrounding fluid are taken up into minute vacuoles.

Question 46

how does exocytosis work?

Answer 46

term form emptying a membrane bound vesicle at the surface of the cell or elsewhere.

Question 47

what is cyanide?

Answer 47

metabolic poison that stops to mitchondria working