unit 1: cell membranes

Question 1

what are membranes and what are they made of?

Answer 1

they are partially permeable barriers made up of phosolipid molecules arrnged in abilayer with embeded proteins

Question 2

describe the fluid mosaic model

Answer 2

FLUID: phospholipids (and proteins) are free to move laterally (side to side)
MOSAIC: proteins have a scattered arrangement within the hospholid bilayer

Question 3

what are phospholipids and their roles?

Answer 3

hydrophgobic tail facing inwards with a hydrophilic head facing outwards arranged in a bilayer.
make the membrane flexiable and self-sealing

Question 4

what is cholesterol and its role?

Answer 4

found in eukaryotic cells for fluidity and stability.
bind to the hydrophobic tails.
stop the membrane being to fluid a high temperatures and stop the membrane being to solid at low temperatures

Question 5

what are glycolipids and their role?

Answer 5

phospholipids with attached carbohydrates.
inter cell signalling and recognision.
cell adhesion: helps to stick cells together.

Question 6

what are intrinsic channel proteins and their role?

Answer 6

channel proteins on the inside of the cell that allow transport hydrophillic and large molecules through the phospholipid bilayer.

Question 7

what are extrinsic channel proteins and their roles?

Answer 7

channel proteins on the outside of the cell.
cell recognision
receptors for signalling between cells and cell adhesion

Question 8

what are glycoproteins and their role?

Answer 8

proteins with attached carbohydrates.
cell signalling and recognision receptors.
binds cells to basement membrane.

Question 8

what is cell signalling?

Answer 8

processes that lead to communication and coordination between cells so that they can work together to trigger a response.
receptors have complementry hormones (insulin receptors

Question 9

Is osmosis active or passive?

Answer 9

Osmosis is a passive process (doesn’t require ATP).

Question 10

what is the definition of osmosis?

Answer 10

Osmosis is the movement of water molecules across a partially permeable membrane from an area of high water potential to low water potential

Question 11

What affects the rate of osmosis?

Answer 11

Temperature/ amount of aquaporins / size of water potential gradient

Question 12

Where can osmosis occur?

Answer 12

Through special channel proteins or through the phospholipid bilayer

Question 13

What is facilitated diffusion?

Answer 13

Easy diffusion of large molecules or charged ions from an area of nigh concentration to low concentration through channel or carrier proteins

Question 14

What affects the rate of facilitated diffusion?

Answer 14

Temperature/ concentration gradient / the number of channel proteins in the membrane.

Question 15

What is simple diffusion?

Answer 15

Passive diffusion from an area of high concentration to an area of low concentration acrossa partially permeable membrane through the phospholipid belayer

Question 16

What is active transport?

Answer 16

The movement of ions or polar molecules from low to nigh concentration against the concentration gradient using ATP

Question 17

What does ATP stand for?

Answer 17

Adenosine tri phosphate

Question 18

What is needed for active transport?

Answer 18

Carrier proteins/protein pumps that only change shape to transport molecules/substances across the membrane

Question 19

What is exocytosis?

Answer 19

The movement of molecules out of the cell using ATP

Question 20

Describe the steps of exocytosis.

Answer 20

1) vesicles made at the Golgi apparatus body to package molecules for transport
2)vesicle moves to the plasma membrane and fuses with it
3)phospholipids now added into plasma membrane and molecules released

Question 21

What is endocytosis?

Answer 21

The movement of molecules into cells

Question 22

How does endocytosis occur?

Answer 22

Molecules adhere to membrane or they can bind to receptors causing vesicle formation