1.1 Carbohydrates 1.2 Lipids

Question 1

what is the structure of glucose (simpler form)

Answer 1

see notes

Question 2

formula for glucose

Answer 2

C6 H12 O6

Question 3

What do all carbohydrates contain?

Answer 3

the elements
carbon
hydrogen
oxygen

Question 4

sugars with 6 carbon atoms are called…

Answer 4

hexose monosaccharides

Question 5

what is a monosaccharide?
and give examples

Answer 5

A single sugar molecule
eg glucose, fructose, galactose

Question 6

Are monsoaccharides soluble in water?

Answer 6

Yes,monosaccharides including glucose have a large number of OH groups(hydroxyl groups) which form hydrogen bonds with water molecules.
And so they are hydrophilic (as hydrophilic molecules all dissolve in water)

Question 7

some monosaccharides contain 5 carbon atoms…which are known as… give example

Answer 7

pentose monosaccharides

eg ribose

Question 8

structure of ribose

Answer 8

see notes

Question 9

what are the isomers of glucose

Answer 9

alpha
beta

Question 10

in both alpha and beta carbon 1 is bonded to a hydrogen and an OH group (hydroxyl group)… but whats the difference

Answer 10

see diagram, if hydroxyl group points below the ring the isomer is alpha glucose
if hydroxyl group points above the ring the isomer is beta glucose

Question 11

draw alpha and beta

Answer 11

see diagram

Question 12

what is formed when two
monosaccharides react together

Answer 12

diasaccharide

Question 13

when two alpha glucose molecules react together we get…

Answer 13

the disaccharide maltose

Question 14

when we make a disaccharide we also produce a molecule of…

what type of reaction is this…

Answer 14

water

condensation reaction

Question 15

draw what happens when two monosaccharides react together

Answer 15

see diagram

Question 16

between the water molecules we formed a new bond called a…

Answer 16

glycosidic bond

Question 17

how to determine the number on glycosidic bond

refer to diagram

Answer 17

where the bond lies on carbon atom eg 1,4 glycosidic bond

Question 18

what happens if we add water to a disaccharide

what type of reaction is this

Answer 18

we can break the glycosidic bond
which converts the disaccharide back to the original monosaccharide
this is known as a hydrolysis reaction

Question 19

how is sucrose (disaccharide) formed

Answer 19

from the monosaccarides
glucose and fructose

Question 20

how is lactose (disaccharide) formed

Answer 20

from the monosaccarides
glucose and galactose

Question 21

is glucose soluble in water?

Answer 21

yes, glucose is extremely soluble in water as it contains a large number of hydroxyl groups

Question 22

are hydroxyl groups polar?

Answer 22

yes due the small negative charge on the oxygen atom and the small positive charge on the hydrogen atom
which means hydroxyl groups can form hydrogen bonds with water molecules.

this makes glucose hydrophilic

Question 23

what two molecules consist of starch (polysaccharide)

Answer 23

amylose and amylopectin

Question 24

what is amylose

Answer 24

amylose is an unbranched ploymer of alpha glucose molecules.

if we join together a large number of alpha glucose molecules then we make the polysaccharide amylose

1,4 glycosidic bonds
the amylose molecule then twists into a compact helix- with hydrogen bonds forming between the glucose moleucles along the chain.

starch is a store of glucose- when the cell needs glucose water is used to break the glycosisdid bonds- tis is known as a hydrolysis reaction.

Question 25

to separate starch and glucose
what type of reaction is this

Answer 25

starch is a store of glucose- when the cell needs glucose water is used to break the glycosisdid bonds- tis is known as a hydrolysis reaction.

Question 26

draw structure of amylose

Answer 26

see notes

Question 27

structure of amylopectin

Answer 27

see notes

Question 28

what is amylopectin

Answer 28

its a branched polymer of alpha glucose joined by 1-4 glycosidic bonds
it is branched every 25-30 glucose molecules
A branch is another chain of alpha glucose molecules joined by 1-4 glycosid bonds
but its connected to the main chain by glycosidic bond of 1,6

Question 29

How is the structure of starch related to its function?

Answer 29

amylose forms a tight helix and this makes starch compact- starch can store a large amount of glucose molecules for its size
starch is insoluble in water- starch does not cause water to enter the cell by osmosis- because amylose and amylopectin are polymers they are too large to diffuse through the cell membrane and pass out of the the cell.

Question 30

what happens when the cell needs glucose

what type of reaction

Answer 30

enzymes are used to break the glycosidic bonds in starch- this is a hydrolysis reaction and requires water
the enzymes which break down the starch act at the ends of molecules.
because amylopectin has large number of branches it means it has a large number of ends- and because of this enzymes can break down starch rapidly.

Question 31

what is glycogen

Answer 31

glycogen is a polymer of alpha glucose
most of the alpha glucose molecules are joined by 1,4 glycosidic bonds

glycogen also contains branches
and the glucose molecules at the branch points are joined by 1,6 glycosidic bonds.

glycogen is more branched than amylopectin which makes glycogen a very compact molecule
because glycogen has a large number of branches, it has a lotof free ends; this means that enzymes can convert glycogen back to glucose very rapidly.

unlike glucose, glycogen is insoluble in water-this means the glycogen does not draw water into cells by osmosis.

being a large molecule, glycogen cannot diffuse out of a cell.

Question 32

in animals the glucose storage molecule is called…

Answer 32

glycogen- the major stores of glycogen are found in the liver and in muscle cells

Question 33

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draw structure of glycogen

Answer 33

see notes

Question 34

cellulose is major part of the cell wall found in plant cells. what is its structure

Answer 34

cellulose is a polymer of beta glucose
it is unbranched polysaccharide
because beta the oh group will be above the ring which means it cannot form a bond to the neighbouring beta group so every second molecules flips to form a 1,4 glycosisdic bond when you have the third you do not need to flip the bta glucose molecule to form a glycosidic bond between carbon 1 and carbon 4

Question 35

draw the structure of cellulose

Answer 35

refer to diagram

Question 36

cellulose is straight chain…

Answer 36

which allows cellulose molecules to get close together
hydrogen bonds can now form between the neighbouring chains
because a huge number of hydrogen bonds form this makes cellulose extremely strong
when cellulose chains group together scientists call this a microfibril. Microfibrils then group together to form larger structures called macrofibrils. Macrofibrils group together to form a cellulose fibre.

Cellulose cell wall is also permeable to molecules eg water. As water moves the plant cell contents push outwards against the cell wall. The strength of the cellulose cell wall means that it can resist outwards pressure due to the cell contents. This prevents the plant cell from bursting. When a plant cell is full of water, it becomes rigid. Scientists say that the plant cell is turgid. These turgid plant cells. Help to give the plant its upright structure.

Question 37

how do triglcyerides

Answer 37

condenstation reaction between 1 molecule of glycerol and 3 fatty acids which from an ester bond

Question 38

contrast saturated and unsaturated fatty acids

Answer 38

saturated
- contain only single bonds
- straight chain molecules
-higher meting point= solid at room temerature

unsaturated
- contain C=C double bonds
- kinked molecules have fewer contact points
-lower melting point = liquid at room temerature
- found in plant oils

Question 39

relate the structure and function of triglycerides

Answer 39

high energy mass: ratio = high calorfifc value from oxidation
insoluble hydrocarbon chain= no effect on water potential of cells and used for water proofing

Question 40

describe structure and function of phospholipids

Answer 40

glycerol backbone attaches to 2 hydrophobic fatty acids tails and one 1 hydrophilic polar phosphate head
forms phospholidid bi layer
tails splay outwards = water proofing