Topic 4: Cell Membranes and Transport

Question 1

Active Transport

Answer 1

the movement of molecules or ions through transport proteins (carrier and channel protein) across a cell membrane, against the concentration gradient, using energy from ATP

Question 2

Bulk Transport

Answer 2

the movement across the membrane of a large quantity of materials which are taken in or out of the cell by vesicles. this process require energy.
Two type
endocytosis (phagocytosis and pinocytosis)
exocytosis

Question 3

Carrier Protein

Answer 3

a type of membrane protein which changes shape to allow passage into or out of the cell of specific ion or molecules by facilitated diffusion or active transport

Question 4

Cell Adhesion

Answer 4

the process which cells join together to form tissues

Question 5

Cell Marker

Answer 5

some glycoproteins and glycolipids called antigen that give cell its identity and enable cell of similar type to group together to form the tissue

Question 6

Cell Signalling

Answer 6

the molecular mechanism by which cells detect and respond to external stimuli, including communication between cells. carbohydrate chains or membrane protein act as the receptor

Question 7

Cell Surface Antigen

Answer 7

a protein molecule used for cell recognition

Question 8

Cell Surface Receptor

Answer 8

carbohydrate chains help glycolipids and glycoproteins to act as receptor molecules and identify markers for cell

Question 9

Channel Protein

Answer 9

a membrane protein of fixed shape which has a water-filled pore through which selected hydrophilic ions or molecules can pass by facilitated diffusion

Question 10

Cholesterol

Answer 10

a small, lipid-related molecule with a hydrophilic head and a hydrophobic tail which is an essential constitute of membranes, particularly in animal cells, conferring fluidity, flexibility and stability to the membrane

Question 11

Diffusion

Answer 11

the net movement of molecules or ions from a region of higher concentration down a gradient, as a result of the random movements of particles

Question 12

Endocytosis

Answer 12

the bulk movement of liquid (pinocytosis) or solid (phagocytoosis) into a cell, by the infolding of the cell surface membrane to form vesicles containing the substance; endocytosis is an active process requiring ATP

Question 13

Exocytosis

Answer 13

the bulk movement of liquids or solids out of a cell, by the fusion of vesicles containing the substance with the cell surface membrane; exocytosis is an active process requiring ATP

Question 14

Extrinsic Protein (Peripheral Protein)

Answer 14

extrinsic proteins are found on the surface of the membrane only. many are attached to intrinsic protein.

Question 15

Facilitated Diffusion

Answer 15

the diffusion of a substance through transport protein in a cell membrane; the proteins provide hydrophilic areas that allow the molecules or ions to pass through the membrane which would otherwise be less permeable to them

Question 16

Fluid Mosaic Model

Answer 16

the current accepted basic model of membrane structure, proposed by Singer and Nicolson in 1972, in which protein molecules are free to move about in a fluid bilayar of phospholipid molecules. the surface of membrane has a mosaic appearance as it is made up of smaller phosphate heads and larger proteins producing a mosaic effect

Question 17

Gated Protein

Answer 17

part of the protein can move to open or close the membrane usually in response to a signal molecule

Question 18

Glycocalyx

Answer 18

carbohydrate chain forming a sugary coating outside the cell. the chain forms hydrogen bonds with water outside the cell leading to greater stability.

Question 19

Glycolipid

Answer 19

the phospholipid with carbohydrate chain (oligosaccharide) attached. these can act as receptor and recognition molecules

Question 20

Glycoprotein

Answer 20

the protein with a carbohydrate chain (oligosaccharide) these can act as receptor and recognition molecules

Question 21

G Protein

Answer 21

G Protein acts as a switch to bring about the release of a small molecule which diffuses through the cell relaying the message; the switch mechanism involves binding to GTP molecules

Question 22

Incipient Plasmolysis

Answer 22

the point at which pressure potential has just reached zero and the plasmolysis is about to occur

Question 23

Intrinsic Protein (Integral Protein)

Answer 23

the intrinsic protein may be found in one of the monolayers

Question 24

Miscelle

Answer 24

stable sphere structure formed when phospholipid shaken up with water due to hydrophilic heads facing water and hydrophobic tails facing each other away from water

Question 25

Osmosis

Answer 25

the net movement of water molecules from a region of higher water potential to a region of lower water potential, through a partially permeable membrane, as a result of their random motion (diffusion)

Question 26

Phagocytosis

Answer 26

the bulk movement of solid into a cell, by the infolding of the cell surface membrane to form vesicles containing the substance; phagocytosis is an active process requiring ATP

Question 27

Phospholipid Bilayer

Answer 27

the hydrophobic phosphate heads of each layer are orientated to the polar environment that comprise the external and internal environment of the cell; the hydrophobic fatty acid tails point toward each other forming a non-polar hydrophobic interior of the membrane

Question 28

Pinocytosis

Answer 28

the bulk movement of liquid into a cell, by the infolding of the cell surface membrane to form vesicles containing the substance; pinocytosis is an active process requiring ATP

Question 29

Plasmolysis

Answer 29

as the protoplast continue to shrink, it begins to pull away from the cell wall

Question 30

Pressure Potential

Answer 30

the contribution of pressure to the water potential of a solution

Question 31

Protoplasm

Answer 31

the living part of the cell inside the cell wall

Question 32

Sodium Potassium Pump

Answer 32

a membrane protein that moves 3 sodium ions out of a cell and 2 potassium ions into it, using ATP, against the concentration gradient

Question 33

Solute Potential

Answer 33

the extent to which the solute molecules in a solution decrease the water potential of a solution. adding more solute decreases the water potential.

Question 34

Trans-membrane Protein

Answer 34

intrinsic proteins that cross the whole membrane usually used for transport

Question 35

Turgid

Answer 35

when a plant cell is fully inflated with water is described as fully turgid

Question 36

Water Potential ψ

Answer 36

a measure of tendency of water to move from one place to another; water moves from a solution with higher water potential to one with lower water potential; water potential is decreased by addition of a solute and increase the application of pressure