cell and membranes

Question 1

how do dyes help biologists

Answer 1

give a better picture of cells and their insides

Question 2

how were dyes used in the brain

Answer 2

black dye showed separate neurones in the brain, showing the brain was made of different cells

Question 3

what is the zymogen granule

Answer 3

specialised organelle in pancreatic acinar cells for digestive enzyme storage and secretion.

Question 4

what is a tight junction

Answer 4

a junction between animal cells which ensure a watertight seal between two adjacent animal cells. Made of transmembrane proteins which interlink both plasma membranes.

Question 5

what are desmosomes

Answer 5

Junctions which resist tearing by a protein called cadherins which connect the cytoskeleton filaments in each cell.

Question 6

what is a gap junction

Answer 6

channel connecting cells made of tubes called connexins

Question 7

what do gap junctions do

Answer 7

allow passage of electrical and chemical stimuli. this synchronises contractions of smooth muscle responsible for peristaltic movements. and cardiac

Question 8

what is the extracellular matrix

Answer 8

composed of proteins and polysaccharides which are secreted locally and form a meshwork with the cells.

Question 9

how do plant cells communicate

Answer 9

through plasmodesmata

Question 10

what is a protein channel

Answer 10

membrane proteins with a hydrophilic opening which allows hydrophilic molecules to pass through, most are gated

Question 11

what is a carrier protein

Answer 11

membrane protein which changes shape when a molecule binds to it, letting the molecule inside.

Question 12

what carrier protein allows glucose to diffuse

Answer 12

Glut1

Question 13

how is the glucose gradient maintained

Answer 13

glucose is phosphorylated which means that glucose cannot travel back through Glut1

Question 14

what are the three main ways that active transport takes place

Answer 14

coupled transporter
ATP driven pumps
Light-driven pumps

Question 15

what are coupled tranporters

Answer 15

when the transport of one solute is coupled with another to allow movement against gradient. (secondary)

Question 16

what are ATP driven pumps

Answer 16

when energy from hydrolysis of ATP is used

Question 17

why must the electrochemical pump be maintained

Answer 17

if ions flowed down their gradients, this would affect osmotic balance
movement of ions like Na drives movement of other substances

Question 18

how does the Sodium potassium pump work

Answer 18

pumps 3 Na out and 2 K in against conc gradients. Does this by phosphorylation

Question 19

what is an example of secondary active transport (symport)

Answer 19

sodium glucose symporter where glucose is coupled with sodium to allow glucose to flow against conc gradient

Question 20

example of antiport

Answer 20

diffusion of na into cardiac muscle allows ca to leave, this is important in regulating contraction

Question 21

how does digoxin work

Answer 21

this inhibits the sodium potassium pump, increasing the levels of sodium in cells and therefore the sodium calcium antiport is less effective so more calcium inside the cardiac muscle for a contraction

Question 22

how do tight junctions play a role in membrane proteins

Answer 22

prevent movement of proteins such as symporters away from where they are needed.

Question 23

why are cells typically small

Answer 23

to maintain a high surface area to volume ratio

Question 24

what methods can be used to see cells

Answer 24

staining, immunostaining and fluorescence microscopy and fluorescent protein tagging

Question 25

what gives cells their shape

Answer 25

cell wall and cytoskeleton

Question 26

where are the ribosomes made

Answer 26

in the nucleolus

Question 27

outline lysosomes

Answer 27

example of compartmentalization which contain lots of catabolic enzymes in an acidic environment they also have a role in autophagy digestion of both external and internal bodies

Question 28

What is Lysosome storage disease

Answer 28

where a key enzyme is not working and so material accumulates in the lysosome.

Question 29

how do we know all eukaryotic cells are related

Answer 29

genes that are conserved across eukaryotes leave no doubt we come from a last eukaryote common ancestor

Question 30

how is gene expression different in prokaryotes to eukaryotes

Answer 30

translation and transcription are coupled in prokaryotes but in eukaryotes they are separate

Question 31

what is different in eukaryotes with gene expression

Answer 31

RNA can be modified by splicing

Question 32

what is the transmembrane domain

Answer 32

the part of an integral protein which goes through the membrane

Question 33

integral vs peripheral proteins

Answer 33

integral have a part of the protein which passes through membrane but the peripheral proteins arent inserted in membrane may be attached by a lipid or by protein interactions

Question 34

why is a fluid membrane important

Answer 34

allows fusing with other membranes such as vesicles ensured membrane is equally shared in cell division cell migration requires fluid membrane

Question 35

how is the membrane fluidity demonstrated experimentally

Answer 35

using laser beam and bleaching dye the lipids then bleach a part of the membrane using a laser this will prevent the fluorescence but when left for some time, it returns, showing lipids have moved around

Question 36

how do lipids move in the membrane

Answer 36

by rotation, flexion and flip flop

Question 37

what enzymes does flip flop require to work

Answer 37

flipases and flopases

Question 37

what enzymes does flip flop require to work

Answer 37

flipases and flopases

Question 38

what is the problem for pure phospholipid bilayers

Answer 38

they experience rapid phase change over a narrow range of temp

Question 39

how do prokaryotes control membrane fluidity

Answer 39

they synthesise more lipids with smaller chain length and unsaturation in order to decrease van da walls when it is cold. this increases spacing between molecules reverse when temp increases

Question 40

how do eukaryotes regulate the membrane fluidity

Answer 40

using cholesterol at 37 degrees the membrane would be too fluid so it stabilises interactions between phospholipids at lower temperatures, it prevents the molecules from getting too close and becoming hard and immobile

Question 41

what prevents proteins from moving too far along the membrane

Answer 41

tight junctions

Question 42

how does number of tails influence membrane shape

Answer 42

two tails forms a cylinder structure and will form a bilayer 1 tail forms a cone and will interact into a micelle

Question 43

how is membrane asymmetry maintained

Answer 43

scramblases (passive) and flipases and flopases flipases bring PS and PE onto cytosolic side flopases bring SM and PC onto the exoplasmic side

Question 44

outline scramblases

Answer 44

new lipids are only added on the cytosolic side so this must be scrambled scramblases arent specific and transfer phospholipids from one side to the other