Biologcal Molecules - Carbohydrates Flashcards
Carbohydrates are made up of what three elements?
Carbon
Hydrogen
Oxygen
What is carbohydrate structure based on?
Units, monomers, which can join together to form diners & polymers
What is the monomer (single unit) of carbohydrates?
The monosaccharide
Monomer =
Dimer =
Polysaccharide =
Monosaccharide
Disaccharide
Polymer
Explain sugars within carbohydrates
They are monosaccharides and disaccharides
Their characteristics is tasting sweet and being soluble in water
What are complex carbohydrates within carbohydrates?
Polysaccharides
Their characteristics are being not sweet tasting and being insoluble in water
Give examples of monosaccharides
A glucose, B glucose, fructose, Ribose & deoxyribose
(Only need to fully know about A glucose and Ribose)
Why is glucose the most important carbohydrate in our bodies?
Because it is used by the cells as a respiratory substrate.
This means it is gradually broken down, inside cells, to release energy
Why is glucose an example of a hexose sugar?
Because it has 6 carbon atoms
What are the two isomers of glucose?
Alpha glucose and Beta glucose
(Fructose is also an isomer of glucose)
What’s an isomer?
Two molecules with the same molecular formula but differ structurally
what are the structural rules to remember or monosaccharides?
- 6 carbon atoms
- at carbon atom 1, hydrogen is Above for Alpha (whereas Beta hydrogen is Below)
- Fructose is still a hexose even though it is not a “hexagon” based shape because it has 6 carbon atoms
Why are glucose molecules polar & soluble in water ?
Due to the hydrogen bonds that form between the hydroxyl groups and water molecules.
The solubility in water is important because it means glucose is dissolved in the cytosol of the cell
What are Penrose sugars & give examples
Sugars with 5 carbons
Very important ones are ribose and deoxyribose
Go draw the Alpha glucose structure
(Answer in biology book online)
Go draw the structure of ribose
(Answer in the biology book)
where is ribose found?
In the RNA (ribonucleic acid)
What are the differences between ribose and deoxyribose?
- when compared with deoxyribose it can be seen that there is a difference at carbon 2
- deoxyribose has a hydrogen atom instead of a hydroxyl group at C2 - it has one less oxygen atom
- compared to ribose it it deoxygenated - hence the term deoxyribose
- deoxyribose is the sugar found in DNA : (deoxyribonucleic acid)
Give examples of hexose and the amount of carbon atoms
6 CARBON ATOMS
Alpha glucose
Beta glucose
Fructose
Galactose
Give examples of pentose + amount of carbon atoms
- ribose
- deoxyribose
Give examples of triode and the amount of carbon atoms
- triose phosphate
- glycerine 3 phosphate
Why is glucose a monosaccharide?
As it cannot be broken down further by hydrolysis
Monomers and monosaccharides can be joined to form what?
Diners & Disaccharides
Explain a condensation reaction?
- in order for the two monosaccharides to join together this way, a bond has to form
- this bond is achieved when the hydroxyl group at carbon 1 of one monosaccharide and the hydroxyl group of carbon atom 4 of the other monosaccharide react together
- between them, the two hydroxyl groups donate to hydrogen atoms, and one oxygen atom, the atoms combine together to make H2O water
What does the 1-4 glycosidic bond mean?
It refers to the number of the carbon atom within the molecules between which the bond is formed
So carbon one of one glucose is joined to carbon four of the other glucose
What happens in a condensation reaction?
Glycosidic (covalent) bond is formed
Water is eliminated (released)
What happens in the hydrolysis reaction?
- glycosidic (covalent) bond broken
- water used up
What are the disaccharides made of?
MALTOSE : a glucose + a glucose
SUCROSE : a glucose + fructose
LACTOSE : a glucose + galactose
What’s sucrose?
A disaccharide which is made from monosaccharides which are different to one another is sucrose
What are polysaccharides?
We have already seen that monosaccharides can undergo condensation reactions to become disaccharides
Further condensation reactions with more monosaccharides will build up a carbohydrate, polymer or polysaccharide
Important polysaccharides are : starch, glycogen, and cellulose 
What is starch and what are the two types?
Starch is a polymer of glucose molecule made by plants
The two types of glucose polymers within starch are amylose and amylopectin
Many alpha glucose molecules can be joined by Glycosidic bonds to form two slightly different polysaccharides known collectively as starch .
What are the features of amylose?
- linear chains
- coil up into a helix
- helix maintained by hydrogen bonds
- joined by 1-4 glycosidic bonds (no branches)
What are the features of amylopectin?
Joined together by 1-4 glycosidic bonds with some branching achieved by 1-6 glycosidic bonds
What is glycogen?
Is a polymer of glucose molecules made by animals
It was joined by a 1-4 glycosidic bonds with frequent branching achieved by a 1-6 glycosidic bonds
It is very similar to amylopectin in structure
Glycogen is stored in liver / muscle cells
Why do we store it as glycogen instead of glucose?
- it is insoluble, so it does not affect water potential of cells (doesn’t affect osmosis)
- It is compact, so a lot of glucose can be stored in a small place
- It is a branched molecule, so there’s a lot of “ends” where glucose can be quickly released when needed
What is needed to convert glucose to glycogen and vice versa?
GLUCOSE TO GLYCOGEN:
Insulin is needed
GLYCOGEN TO GLUCOSE:
Glucagon is needed
Glucose is a soluble monosaccharide found in the blood
Glycogen is insoluble and found in the liver & muscle cells
What is glucose?
And how do the levels in the blood work?
- glucose is used as a respiratory substrate it is broken down during respiration to release energy
- our diet supplies the respiratory substrate we require to stay alive. During digestion, the carbohydrate components of a diet, a broken down into simple sugars, including glucose.
- Some of those glucose will be used up immediately within respiring cells. There must always be enough glucose in the blood sustain the respiring cells. (Particularly brain cells.)
- However, too much glucose in blood is harmful to brain cells, the retinas, and the glomerulus (filtering unit within the kidney) so it is important to keep the levels of glucose in the blood within a range of narrow parameters
- When blood glucose levels are high, for example, after carbohydrate rich meal, glucose is taken it out of the blood and converted into glycogen
When blood glucose levels are low, for example, after a timer fasting like sleep or after a long period of exercise, glycogen is broken down into glucose, which is then released into the bloodstream
What is cellulose?
Selling those is made up of beta glucose molecules. This has implications on the orientation of the glucose molecules within the polysaccharide chain.
Explain the structure of beta glucose on the polysaccharide chain
When beta glucose molecules which are orientated in the same way, I’m not place together. It is not possible to make a Glycosidic bond. This is because the two hydroxyl groups are not increase proximity with one another.
But when alternate beta glucose molecules are flipped over by 180°, then the two hydroxyl groups are brought together. Every other one is flipped over.
This allows condensation reactions to occur from Glycosidic bonds. These are 1-4 glycosidic bonds
Explain how fibrils are made
Cellulose molecules do not coil. They live straight because the glucose monomers contains so many hydroxyl groups lots of hydrogen bonds form between neighbouring cellulose molecules.
This produces bundles of 60 to 70 cellulose molecules, laying side-by-side all held together by thousands of hydrogen bonds
These bundles are called fibrils
(Hydrogen bonds form in cross bridges between cellulose molecules)
How are fibres made?
The cellulose molecules bundle together to make fibrils, these are maintained by hydrogen bonds
The fibrils bundle together to make fibres more hydrogen bonding maintains these. You can see the fibres in micrographs of cellulose cell walls.
Why are cellulose fibres so strong?
They are very strong because of all the hydrogen bonds
The cellulose fibres are embedded in pectins to form the cell wall
(Proteins that act as a glue)
I live in criss-crossing, layers for extra strength from busting on water moves into it by osmosis - it has to be able to stand turgor pressure
How are the cellulose fibres fully permeable?
There are gaps between the cellulose fibres, which account for it being fully permeable
Why is cellulose difficult to digest?
Cellulose is difficult to digest because mamusia do not make the enzyme cellulase- this is the enzyme which is required to break beta 1-4 glycosidic bonds because 1-4 glycosidic bonds don’t fit through the amylase enzyme
FOR AMYLOSE GIVE:
The monosaccharide from which it is formed
Types of glycosidic bonds
Overall shape
Solubility
Function
Hydrogen bonding within or between molecules
Alpha glucose
A 1-4
Helix
Insoluble
Energy store in plants
Hydrogen bonds between sugar units in the chain
FOR CELLULOSE GIVE:
The monosaccharide from which it is formed
Types of glycosidic bonds
Overall shape
Solubility
Function
Hydrogen bonding within or between molecules
- Beta glucose
- B 1-4
- straight chain
- insoluble
- forms cell walls
- hydrogen bonds between sugar units in different chains
FOR GLYCOGEN GIVE:
The monosaccharide from which it is formed
Types of glycosidic bonds
Overall shape
Solubility
Function
Hydrogen bonding within or between molecules
- a glucose
- a 1-4 with a 1-6 at branches
- branched and slightly coiled
- insoluble
- an energy store in animal cells
- some hydrogen bonds between sugar units in the chain