Biological molecules - Carbohydrates Flashcards
(37 cards)
1
Q
What carbohydrates made out of
A
Contain carbon, hydrogen and oxygen
2
Q
What does “Hydrated carbon” mean
A
for every carbon atom there is two hydrogen atoms and one oxygen atoms
3
Q
What are the functions of carbohydrates
A
- Source of energy
- Store of energy
- Structural units
- some are also part of other molecules such as nucleic acid and glycolipids
4
Q
What are the main groups of carbohydrates
A
- monosaccharides
- disaccharides
- polysaccharides
5
Q
Describe a monosaccharide
A
- Simplest carbohydrate
- Important in living things as a source of energy – large number of carbon and hydrogen bonds
- Sugars which are sweet tasting and are soluble in water and are insoluble in non-polar solvents
- Exists as rings, straight chains or cyclic forms
- One double bonded to an oxygen to form a carbonyl group
6
Q
Name a sugar with
A 6 carbon atoms
B 5 carbon atoms
C 3 carbon atoms
A
A Hexose
B Pentose
CTriose
7
Q
Monosaccharides are the monomers of ……
A
More complex carbohydrates, they bond together to form disaccharides or polysaccharides
8
Q
What monosaccrides exist as straight lines and what monosaccharides exist as ring or cyclic form
A
- Triose and tetrose sugars exist as straight chains but hexose and pentose are more likely to be found in a ring or cyclic form – in both forms glucose can exist as a number of different isomers, in the straight chain form the H and OH can be reversed, ring shape isomers can also form
9
Q
Why are there two isomers of glucose
A
- Because the OH and the H group on carbon 1 can be above or below the plane of the ring when the ring is formed therefore there is alpha and beta glucose – this is important when glucose polymerises into starch or cellulose
10
Q
Describe some properties of disaccharides
A
- disaccharides are sweet and soluble
- Most common disaccharides are maltose, sucrose and lactose
- Maltose and Lactose are reducing sugars whereas sucrose is a non-reducing sugar
11
Q
How are disaccharides made
A
- They are made when two monosaccharides join together
- When they join together a condensation reaction happens and forms a glyosidic bond
- Two Hydroxyl groups line up next to each other and a water molecule is removed, therefore the oxygen atom acts as a link between the two monosaccharide units
- Disaccharides are broken into monosaccharides by a hydrolysis reaction – this is when water is added, the water provides a hydroxyl group, OH, and a Hydrogen, H, this helps the glycosidic bond to break
12
Q
Draw HOW A DISACCHARIDE IS MADE
A
DRAW IT
13
Q
Describe alpha glucose (MONOSACCHARIDES)
A
- hexose
- C6H12O6
- draw it
- energy source component of starch and glycogen these act as energy stores
14
Q
Describe beta glucose (MONOSACCHARIDES)
A
- hexose
- C6H1206
- Draw it
- energy source component of cellulose which provides structural support in plant cell walls
15
Q
Describe Ribose (MONOSACCHARIDES)
A
- pentose
- C5H10O5
- DRAW IT
- component of ribonucleic acid (RNA) ATP and NAD
16
Q
Describe Deoxyribose (MONOSACCHARIDES)
A
- Pentose
- C5H10O4
- DRAW IT
- component of DNA
17
Q
What are polysaccharides
A
- Polymers of monosaccharides, they are monosaccharides joint together
18
Q
What is a homopolysaccharide
A
Polysaccharides that are only made up of one kind of monosaccharides
19
Q
What is a heteropolysaccharide
A
Polysaccharides that are made up of more than one kind of monomer
20
Q
What is polysaccharides used for in energy
A
- Glucose is a source of energy as it is a reactant in respiration – the energy released is used to make ATP which is the energy currency of the cell
- When you join lots of glucose molecules together into polysaccharides uou create a store of energy,
21
Q
Where do plants and humans store the energy and in what form do they store the energy
A
- Plants store energy in chloroplasts and in membrane bound starch granules whereas humans store energy as glycogen in the cells of muscles and in the liver
22
Q
Why are polysaccharides good energy stores
A
- Glycogen in animals and starch in plants (amylose or amylopectin) form large granules
- Glycogen and starch are compact therefore they do not occupy a large amount of space – dense granules in the cell
- Polysaccharides hold glucose molecules in chains, therefore they can easily be snipped off from the chain when wanted for respiration this happens by hydrolysis. Hydrolysis reactions are always catalysed by enzymes
- Some chains are branched (amylose) and some are unbranched (amylopectin and glycogen) branched chains are more compact, and offer the chance for lots of glucose molecules to be snipped of at the same time by hydrolysis when lots of energy is required quickly
23
Q
What enzyme is responsible for hydrolysing 1-4 glycosidic linkages
A
Amylase
24
Q
What enzyme is responsible for Hydrolysing 1-6 glycosidic linkages
A
glucosidase
25
Why is polysaccharides les soluble in water than monosaccharides
- Polysaccharides are less soluble in water than monosaccharides - this is because of their size and because of the regions that could hydrogen bond with water are hidden inside the water molecule
- Amylose may form a double helix which prevents a hydrophobic external surface in contact with the solution
- If many glucose molecule did dissolve in the cytoplasm then the water potential would reduce and excess water would diffuse in this would prevent the normal workings of the cell
26
Describe Amylose and its structure
- in plants
- alpha glucose molecules
- glycosidic bonds between carbons 1-4
- coils into a spiral shape
- hydrogen bonds hold the spiral shape together
- hydroxyl groups on carbon 2 are situated inside the coil this makes it less soluble and allows the hydrogen bonds to maintain coil
27
Describe Amylopectin and its structure
- in plants
- like amylose with glycosidic bonds between carbons 1 and 4 in addition it has branches formed between carbons 1 and 6
- coils into spiral shape - held together by hydrogen bonds, has branches emerging from spiral
28
Describe glycogen and its structure
- in animals
- glycosidic bonds between carbons 1 and 4, and branches formed by glycosidic bonds between carbons 1 and 6
- 1-4 bonded chains tend to be smaller than amylopectin therefore they have less tendency to coil,
- more branched chains this makes it more compact
- easier to remove monomer units as more ends
29
Where is cellulose found, why is cellulose found here
- found in plants forming the cell wall
| - tough and insoluble and fibrous substance
30
Is cellulose homopolysaccharide or heteropolysaccharide
Homopolysaccharide
31
Why wont cellulose spiral like alpha glucose
- Hydrogen and hydroxyl groups on carbon 1 are inverted in beta glucose, this means that every other beta glucose molecule in the cahin is rotated by 180 degrees – this and beta 1-4 glycosidic bonds stop the chain from spiralling
- Hydrogen bonding between the rotated beta molecules in each chain gives the chain additional strength and stops it from spiralling
- Hydrogen bonding between the rotated beta – glucose molecules in different chains fives the whole structure strength – the hydroxyl group on the carbon 2 sticks out and enables the hydrogen bonds to be formed between chains
32
Draw Cellulose
DRAW IT
33
When 60-70 cellulose chains are bound together what do they form
they form a microfibrils: 10-30 nanometre in diameter – these bundle together in the microfibrils which are embedded in pectin’s to form plant cell walls – run in all directions criss-crossing the wall for extra strength
34
Name the structure and function of plant cell walls
- Microfibrils and macrofibrils have very high tensile strength both because of the strength of the glycosidic bonds but also because of the hydrogen bonds between chains – macrofibrils are stronger than steel wire of the same diameter
- Macrofibrils run in all directions, criss-crossing the wall for extra strength
- Difficult to digest cellulose because the glycosidic bonds between the glucose molecules are not easy to break
- Because plants do not have a rigid skeleton each cell needs to have strength to support the whole plant
- There is space between the macrofibrils for water and mineral ions to pass on their way into and out of the cell – makes the cell permeable
- Wall has high tensile strength this prevents plant cells from bursting when they are turgid and support the whole plant – turgid cells press against each other to support the structure of the plant as a whole – this protects the delicate cell membrane
- The macrofibril structure can be reinforced with other substances for extra support or to make the cell walls waterproof, in woody parts of tree trunks cell walls are extra thick to withstand the weight
35
What are the real world uses of cellulose
- Cellulose strength has been exploited by humans for some time – cotton is 90% cellulose
- Cellophane and celluloids are also derived from cellulose
- Papers main component is cellulose
- Rayon (viscose) is a semi-synthetic fibre produced from cellulose (similar properties to silk)
36
What are bacterial cell walls made out of
- The structure surrounding the cell is called a peptidoglycan and is made from long polysaccharide chains that lie in parallel, they are cross-linked by short peptide chains
37
What are exoskeletons made out of
- Insect and crustacean exoskeletons are made from chitin, it has an acetylamino group on carbon 2 instead of a hydroxyl group like cellulose, forms cross links between long parallel chains of acetyglucosamine in a similar way to cellulose
