1.3-Cell membranes and transport

Question 1

Define Fluid?

Answer 1

Because phospholipid molecule within a layer can move relative to each other.

Question 2

Define musaic?

Answer 2

Because proteins within phospholipid layer are of different sizes, shapes and form different patterns.

Question 3

Define cell membrane?

Question 4

Fluid mosaic model?

Answer 4

1.Extrinsic protein
2.Intrinsic protein (Channel / carrier proteins)
3.Cholestrol
4.Glycoprotein
5.Phospholipid Bilayer

Question 5

Extrinsic Protein?

Answer 5

Those with sugars attached glycoproteins form glycocalyx layer of membrane which has role in cell-to-cell recognition or hormone receptor sites.

Question 6

Intrinsic protein: Channel protein

Answer 6

-Channel protein pores lined with polar hyophilic groups that allow charged ions through eg Na+.

Question 7

Carrier protein:

Answer 7

Allow large polar molecules through, eg water soluble sugars and amino acids.

Question 8

Cholesterol:

Answer 8

Found in between phospholipid making it rigid and stable, less fluidity, membrane less permeable.

Question 9

Permeability increase by:
Lipid soluble substances:

Answer 9

(Vit A) and small molecules (O and co2) and move directly through phospholipid bilayer.

Question 10

Water soluble substances:

Answer 10

(Glucose, ions, polar molecules) cant pass through hydrophobic fatty acids tails and so must use intrinsic proteins to pass through.

Question 11

Active transport?

Answer 11

Movement of molecules against concentration gradient from low conc to high conc. Process require energy in form of ATP from respiratory.

Question 12

Graph (AT):
Trend seen

Answer 12

-Mineral s ion taken by active transport.
-Active transport need energy ATP.
-ATP made in respiration, so no respiration, no ATP, no uptake.

Question 13

Diffusion?

Answer 13

Movement of molecules from region of low concentration to high region down a conc gradient. Passive process requires no ATP, occurs through Phospholipid bilayer.

Question 13

Diffusion increase by:

Answer 13

-Thinner membrane
-Small molecules
-LSA
-Inc temp
-Higher conc gradient

Question 14

Facilitated diffusion?

Answer 14

Movement of molecules from a region of high conc to a region of low conc down a conc gradient. Passive process directly through phospholipid bilayer (Carrier protein or channel) used
Difference with substances enter cell through protein channels.

Question 15

Co-transport?

Answer 15

Type of facilitated diffusion.
Eg. molecule of glucose and 2 Na ions attaching to carrier protein on outer side of membrane. This changes shape of protein enough to flip them to inside membrane. Then can diffuse separately through cell.

Question 16

Osmosis?

Answer 16

Passive movement of water molecules across semi-permeable membrane, from a region of high water potential to a region of low water potential, until equilibrium is reached.

Question 17

Water potential?

Answer 17

used in formulae; Ψ = ΨS + ΨP.
Scale 0=Pure
-300= some dissolved solutes
-800= more solute are in solution more - water potential.

Question 18

In plant cell, Turgid?

Answer 18

In hypotonic cells take up water by osmosis.
Pressure potential inc as cytoplasm pushes on cell wall.

Question 19

Incipient plasmolysis?

Answer 19

Cell has lost enough water from cell membrane to start being drawn away from cell wall.
This lower the pressure potential to 0.

Question 20

Plasmolysed?

Answer 20

Cell in hypertonic (more conc) solutions become flaccid(floppy).

Question 21

In animal cell?

Answer 21

it is important animal
cells are in an isotonic solution (same
concentration of dissolved solutes inside and
outside cell) as they lack a cell wall. Cells can
burst in hypotonic and shrink in hypertonic
solutions due to osmosis.

Question 22

Tonicity?

Answer 22

– refers to concentration of solute

Question 23

Hypertonic?

Answer 23

-means high conc of solute and .’. low WP.

Question 24

Hypotonic?

Answer 24

-means low conc of solute and .’. high WP.

Question 25

Isotonic?

Answer 25

-means same conc of solute and same low WP, so no movement of water between 2 solutions.

Question 28

Bulk transport, Endocytosis?

Answer 28

1-phagocytosis, solids enters cell.
2.Pinocytosis, liquid enter cell.
-Plasma membrane folds inwards.
-Plasma membrane engulfs the material.
-Vesicle formed from plasma membrane enter cell.

Question 28

Exocytosis?

Answer 28

1Vesicle formed from Golgi moves towards plasma membrane.
2Vesicle fuses with plasma
membrane.
3. Vesicle contents empty out of cell.

ATP is required to move the vesicles so
this is an active process.