B1.1 Carbs and lipids

Question 1

glucose+glucose

Answer 1

maltose

Question 2

glucose+fructose

Answer 2

sucrose

Question 3

glucose+galactose

Answer 3

lactose

Question 4

glycogen(4)

Answer 4

alpha joined by 1, 4 and 1,6 glycosidic bonds; many side branches=energy can be released quickly as enzymes can act simultaneously on the branches; large and compact=store lots of energy; insoluble=wont affect water potential of cells and can’t diffuse out of cells

Question 5

amylose

Answer 5

unbranched, 1,4 bonds, coiled, very compact=stores a lot of energy

Question 6

amylopectin

Answer 6

branched, 1,4 and 1,6 bonds, many side branches can be acted on simultaneously by many enzymes and broken down to release its energy

Question 7

key properties of starch(3)

Answer 7

insoluble so doesn’t affect cell water potential, compact so lots of energy can be stored in a small space, when hydrolysed the released alpha glucose can be transported easily

Question 8

cellulose

Answer 8

long, unbranched, beta glucose

Question 9

what are microfibrils

Answer 9

strong threads made of long cellulose chains running parallel to each other, joined by hydrogen bonds forming strong cross linkages

Question 10

why is cellulose important?

Answer 10

stops cell wall from bursting under osmotic pressure, bc it exerts inward pressure that stops the influx of water so cells stay turgid and rigid maximising the SA for photosynthesis

Question 11

what is Benedict’s reagant?

Answer 11

alkaline solution of copper(II) sulfate; when a reducing sugar is added to this and heated it forms an insoluble red precipitate copper(I) oxide

Question 12

test for reducing sugars

Answer 12

add food sample in liquid form, add Benedicts, heat mixture in a water bath for 5 mins, if solution turns brick red then reducing sugar is present

Question 13

test for non-reducing sugars

Answer 13

add food sample to dilute HCl; water bath for 5 mins; (dilute HCl will hydrolyse the disaccharides and polysaccharides into their constituent monosaccharides); add sodium hydrogencarbonate to neutralise the test tube bc Benedicts wont work in acidic conditions; pH paper used to check solution is neutralised; solution is retested: add benedicts and put in water bath for 5 mins if non-reducing sugar is present colour change from blue to brick-red

Question 14

why are unsaturated lipids liquid at room temp?

Answer 14

presence of a double bond means molecule can bend, so unsaturated fats can’t pack tightly together and are liquid at room temp

Question 15

triglyceride properties(2)

Answer 15

low mass to energy ratio=good storage bc a lot of energy being stored in a small volume=less mass for animals to move around; large and non-polar=insoluble in water so storage doesn’t affect water potential of cells

Question 16

test for lipids(emulsion)

Answer 16

add sample and ethanol; shake tube to dissolve all the lipid; add water and shake; cloudy-white=presence of a lipid

Question 17

which type of fatty acid in the diet are positively correlated with an increased risk of CHD?

Answer 17

saturated and trans unsaturated

Question 18

what are the properties of monosaccharides?

Answer 18

colourless crystalline molecules, soluble in water(eg glucose)

Question 19

role of glycoproteins?

Answer 19

receptor molecules in cell recognition, cell signaling and endocytosis

Question 20

how do glycoproteins act as antigens?

Answer 20

they can identify cells as either ‘self’ or non-self, cells that are non-self will trigger an immune response in organism

Question 21

blood types:

Answer 21

A have type A glycoprotein antigens, blood type B have type B glycoprotein antigens, type AB have both types, type O have neither

Question 22

what happens if blood of the wrong type enters the body?

Answer 22

antibodies cause the incorrect antigens(from transfused blood) to clump together blocking blood vessels

Question 23

which large non-polar molecules can pass through the phospholipid bilayer?

Answer 23

steroid hormones which contain cholesterol and the hydrocarbon region of cholesterol is non-polar allowing it to cross lipid bilayers

Question 24

what are 2 examples of steroid hormones and why can they cross the lipid bilayer?

Answer 24

oestradiol and testosterone, produced by gonadal tissues in reproductive organs, bc of their lipid structure they can pass, inside the nucleus these hormones alter and direct the process of transcription