polysaccharides and glycolipids

Question 1

condensation reaction

Answer 1

● 2 molecules join together
● Forming a chemical bond
● Releasing a water molecule

Question 2

monosaccharides

Answer 2

Monomers from which larger carbohydrates are made
● Glucose, fructose, galactose

Question 3

What are disaccharides and how are they formed?

Answer 3

Two monosaccharides joined together with a glycosidic bond
● Formed by a condensation reaction, releasing a water molecule

Question 4

Maltose

Answer 4

Glucose glucose

Question 5

Sucrose

Answer 5

Glucose friction

Question 6

Lactose

Answer 6

Glucose galactose

Question 7

What are polysaccharides and how are they formed?

Answer 7

● Many monosaccharides joined together with glycosidic bonds
● Formed by many condensation reactions, releasing many water molecules

Question 8

Starch structure

Answer 8

● Polysaccharide of α-glucose
● Some has 1,4-glycosidic bonds so is unbranched (amylose)
● Some has 1,4- and 1,6-glycosidic bonds so is branched (amylopectin)
Energy store in plant cells

Question 9

Starch s2f

Answer 9

● Helical → compact for storage in cell
● Large, insoluble polysaccharide molecule → can’t leave cell / cross cell membrane
● Insoluble in water → water potential of cell not affected (no osmotic effect)

Question 10

Glycogen s2f

Answer 10

● Branched → compact / fit more molecules in small area
● Branched → more ends for faster hydrolysis → release glucose for respiration to
make ATP for energy release
● Large, insoluble polysaccharide molecule → can’t leave cell / cross cell membrane
● Insoluble in water → water potential of cell not affected (no osmotic effect)

Question 11

Glycogen structure

Answer 11

Energy store in animal cells

● Polysaccharide made of α-glucose
● 1,4- and 1,6-glycosidic bonds → branched

Question 12

Cellulose

Answer 12

● Provides strength and structural support to plant / algal cell walls
Structure
● Polysaccharide of β-glucose
● 1,4-glycosidic bonds so forms straight, unbranched chains
● Chains linked in parallel by hydrogen bonds, forming microfibrils

Question 13

Cellulose s2f

Answer 13

● Every other β-glucose molecule is inverted in a long, straight, unbranched chain
● Many hydrogen bonds link parallel strands (crosslinks) to form microfibrils (strong fibres)
● Hydrogen bonds are strong in high numbers
● So provides strength to plant cell walls

Question 14

Reducing sugar test

Answer 14

Monosaccharides maltose lactose

1. Add Benedict’s solution (blue) to sample
2. Heat in a boiling water bath
3. Positive result = green / yellow / orange / red precipitate

Question 15

Non reducing

Answer 15

Sucrose

1. Do Benedict’s test (as above) and stays blue / negative
2. Heat in a boiling water bath with acid (to hydrolyse into reducing sugars)
3. Neutralise with alkali (eg. sodium bicarbonate)
4. Heat in a boiling water bath with Benedict’s solution
5. Positive result = green / yellow / orange / red precipitate

Question 16

Name two groups of lipids

Answer 16

Triglycerides and phospholipids

Question 17

How to trigycleride form

Answer 17

● 1 glycerol molecule and 3 fatty acids
● 3 condensation reactions
● Removing 3 water molecules
● Forming 3 ester bond

Question 18

How does structure of triglyceride relate to function

Answer 18

● High ratio of C-H bonds to carbon atoms in hydrocarbon chain
○ So used in respiration to release more energy than the same mass of carbohydrates
● Hydrophobic / non-polar fatty acids so insoluble in water (clump together as droplets, tails inwards) ○ So no effect on water potential of cell (or can be used for waterproofing)

Question 19

How do properties of phospholipid relate to s2f

Answer 19

Function: form a bilayer in cell membrane, allowing diffusion of lipid-soluble (non-polar) or very small substances and restricting movement of water-soluble (polar) or larger substances

Question 20

Lipid test

Answer 20

Add ethanol
Add water
Shale
White cloudy emulsion

Question 21

Fluid mosaic model

Answer 21

● Molecules free to move laterally in phospholipid bilayer
● Many components - phospholipids, proteins,
glycoproteins and glycolipids

Question 22

Describe the arrangement of the components of a cell membrane

Answer 22

● Phospholipids form a bilayer - fatty acid tails face inwards, phosphate heads face outwards
● Proteins
○ Intrinsic / integral proteins span bilayer eg. channel and carrier proteins
○ Extrinsic / peripheral proteins on surface of membrane
● Glycolipids (lipids with polysaccharide chains attached) found on exterior surface
● Glycoproteins (proteins with polysaccharide chains attached) found on exterior surface
● Cholesterol (sometimes present) bonds to phospholipid hydrophobic fatty acid tai

Question 23

Arrangement of phospholipids in cell membrane

Answer 23

● Bilayer, with water present on either side
● Hydrophobic fatty acid tails repelled from water so point away from water / to interior
● Hydrophilic phosphate heads attracted to water so point to water

Question 24

Explain the role of cholesterol (sometimes present) in cell membranes

Answer 24

● Restricts movement of other molecules making up membrane
● So decreases fluidity (and permeability) / increases rigidity

Question 25

How is cell membrane adapted to other functions

Answer 25

● Phospholipid bilayer is fluid → membrane can bend for vesicle formation / phagocytosis ● Glycoproteins / glycolipids act as receptors / antigens → involved in cell signalling / recognition

Question 26

How does movement across cell membrane occur by simple diffusion

Answer 26

● Lipid-soluble (non-polar) or very small substances eg. O2, steroid hormones ● Move from an area of higher concentration to an area of lower conc., down a conc. gradient ● Across phospholipid bilayer ● Passive - doesn’t require energy from ATP / respiration (only kinetic energy of substances)

Question 27

Explain the limitations imposed by the nature of the phospholipid bilayer

Answer 27

Restricts movement of water soluble (polar) & larger substances eg. Na+ / glucose ● Due to hydrophobic fatty acid tails in interior of bilayer

Question 28

Describe how movement across membranes occurs by facilitated diffusion

Answer 28

● Water-soluble / polar / charged (or slightly larger) substances eg. glucose, amino acids ● Move down a concentration gradient ● Through specific channel / carrier proteins ● Passive - doesn’t require energy from ATP / respiration (only kinetic energy of substances)

Question 29

Carrier and channel protein role in FD

Answer 29

● Shape / charge of protein determines which substances move ● Channel proteins facilitate diffusion of water-soluble substances ○ Hydrophilic pore filled with water ○ May be gated - can open / close ● Carrier proteins facilitate diffusion of (slightly larger) substances ○ Complementary substance attaches to binding site ○ Protein changes shape to transport substance

Question 30

Movement across cell membrane osmosis

Answer 30

● Water diffuses / moves ● From an area of high to low water potential (ψ) / down a water potential gradient ● Through a partially permeable membrane ● Passive - doesn’t require energy from ATP / respiration (only kinetic energy of substances

Question 31

Movement across cell membrane by active transport

Answer 31

● Substances move from area of lower to higher concentration / against a concentration gradient ● Requiring hydrolysis of ATP and specific carrier proteins

Question 32

Describe the role of carrier proteins and the importance of the hydrolysis of ATP in active transport

Answer 32

1. Complementary substance binds to specific carrier protein 2. ATP binds, hydrolysed into ADP + Pi, releasing energy 3. Carrier protein changes shape, releasing substance on side of higher concentration 4. Pi released → protein returns to original shape Describe how movement across mem

Question 33

Describe how movement across membranes occurs by co-transport

Answer 33

● Two different substances bind to and move simultaneously via a co-transporter protein (type of carrier protein) ● Movement of one substance against its concentration gradient is often coupled with the movement of another down its concentration gradient

Question 34

Explain the adaptations of some specialised cells in relation to the rate of transport across their internal and external membranes

Answer 34

Cell membrane folded eg. microvilli in ileum → increase in surface area ● More protein channels / carriers → for facilitated diffusion (or active transport - carrier proteins only) ● Large number of mitochondria → make more ATP by aerobic respiration for active transport