plasma membranes

Question 1

roles of the cell membrane

Answer 1

• controls what enters and leaves the cell
• involved in cell signalling
• separates the cell contents from the external environment

Question 1

why do organelles within cells have membranes?

Answer 1

• allows for compartmentalisation
• makes metabolism more efficient and prevents reactions from interfering with each other

Question 2

define compartmentalisation

Answer 2

when the conditions inside different organelles differ for different cellular reactions

Question 3

examples of organelles with membranes

Answer 3

• chloroplast
• mitochondria
• vacuole
• vesicles
• lysosomes
• nucleus

Question 4

what are membranes made of?

Answer 4

phospholipids

Question 5

describe the structure of the phospholipid bilayer

Answer 5

• hydrophilic phosphate heads face outwards towards aqueous environment
• hydrophobic fatty acid tails face inwards, forming the hydrophobic core

Question 6

phospholipids are fluid and can _____ over each other

Answer 6

slide

Question 7

typical width of the cell membrane

Answer 7

7nm

Question 8

describe cell signalling

Answer 8

1. protein (NT or hormone) has a complementary shape
2. to the specific receptor on cell memb
3. binds to receptor
4. causes a response

Question 9

peripheral proteins

Answer 9

proteins on surface of membrane

Question 10

intrinsic proteins

Answer 10

proteins embedded in membrane

Question 11

how are intrinsic proteins held in the membrane?

Answer 11

hydrophobic R group interacting with the hydrophobic core

Question 12

transmembrane proteins

Answer 12

visible on both sides of the membrane

Question 13

glycoproteins

Answer 13

protein has carbohydrate or sugar attachment

Question 14

glycolipids

Answer 14

lipid has carb os sugar attachment

Question 15

what do glycolipids and glycoprotein help to do?

Answer 15

stabilise the membrane by forming H-bonds with water molecules

Question 16

what does it mean by membranes are selectively permeable?

Answer 16

• allow some substances to cross easily
• others cross easily
• some don’t cross at all
• control what enters and leave cell

Question 17

examples of substances that must be able to enter through membrane

Answer 17

• oxygen
• water
• glucose
• a.a

Question 18

examples of substances that must be able to leave through membrane

Answer 18

• carbon dioxide
• water
• waste products
• secretions

Question 19

what types of molecules can pass the membrane easily?

Answer 19

molecules that are small, non-polar, lipid soluble
- e.g. steroid hormones

• can squeeze in between fatty acid tails

Question 20

what types of molecules cannot pass the membrane easily?

Answer 20

large/polar/soluble molecules

• too big to squeeze between fatty acid tails/ repelled by lipids

Question 21

why are water molecules unusual?