2.1.2c Carbohydrates Flashcards
Element composition of Carbohydrates
Carbon, Hydrogen, Oxygen
Element composition of Lipids
Carbon, Hydrogen, Oxygen
Element composition of Proteins
Carbon, Hydrogen, Oxygen, Nitrogen, Sulfur
Element composition of Nucleic acids (DNA & RNA)
Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus
What are monomers
Small units which are the components of larger molecules.
Eg. Monosaccharides sa glucose, amino acids & nucleotides
What are polymers
Molecules made from many monomers joined together
Eg. starch, cellulose
Process of monomers into polymers
Polymerization
What is a condensation reaction
A reaction in which 2 molecules join together by a chemical bond with the release of a water molecule.
Eg. when 2 glucose molecules bond tg
What is a hydrolysis reaction
Hydrolysis is the opposite of a condensation reaction & is when water is added to break a chemical bond between 2 molecules
Eg. Carbohydrates can be broken down into their constituent monosaccharides by hydrolysis
See showbie slide 5 to see diagrams of condensation & hydrolysis reactions
What is the basic monomer in carbohydrates
Sugar, otherwise known as a saccharide
What would a single monomer be called
Monosaccharides
mono = 1
O (hexagon)
What would a pair of monomers be called
Disaccharide
When combined in pairs, monosaccharides form disaccharides through a condensation reaction. The 2 monosaccharides are held tg by glycosidic bond
di = 2
O-O
What would a large chain of monomers be called
Polysaccharide - macromolecules consisting of more than 2 sugars (monosaccharides) - often a long chain polymer, joined by glycosidic bonds.
Polysaccharides are NOT SUGARS
poly = many
O-O-O-O-O-O
How do monosaccharides form disaccharides
2 monosaccharides can join tg by a glycosidic bond in a condensation reaction to form a disaccharide. In this process, a molecule of water is produced
How are polymers & disaccharides broken down into monomers
Hydrolysis reaction (breaking chemical bond using a water molecule)
What are the bonds in carbohydrates
Glycosidic bonds
2 Monosaccharides you need to know
GLUCOSE (hexose monosaccharide) *6 carbon atoms in each molecule
RIBOSE (pentose monosaccharide) *5 carbons
see slide 10 to see their diagrams (ribose on page 22)
Different forms of glucose
There are 2 forms (isomers) of the monosaccharide glucose. These are a-glucose (alpha) and B-glucose (beta). They have the same chemical formula, but their structures are slightly different
See slide 11-13 for diagrams of alpha and beta glucose & page 22 cgp
What are isomers
Molecules with the same molecular formula as eachother, but with the atoms connected in a different way
Eg. alpha and beta glucose
3 Disaccharides you need to know
MALTOSE - a disaccharide formed by condensation of 2 glucose molecules
SUCROSE - a disaccharide formed by condensation of glucose & fructose
LACTOSE - a disaccharide formed by condensation of glucose & galactose
3 Polysaccharides you need to know
GLYCOGEN - formed by the condensation of alpha glucose molecules
STARCH - formed by the condensation of alpha glucose molecules
CELLULOSE - formed by the condensation of beta glucose molecules
Different chains in polysaccharides
Macromolecules that are formed by many monosaccharides joined by glycosidic bonds in a condensation reaction to form chains
These chains may be:
- branched or unbranched
- folded (making the molecule compact which is ideal for storage eg. starch & glycogen)
- straight (making the molecules suitable to construct cellular structures eg. cellulose) or coiled
What is the polysaccharide, Glycogen
- The main energy storage molecule in animals
- A multi-branched alpha glucose polymer
What is Glycogen joined by
- Main chains are joined tg by 1,4 glycosidic bonds
- Branches are linked tg by 1,6 glycosidic bonds
Structure of Glycogen
- It has a large no. of side branches meaning that energy can be released quickly as enzymes can act simultaneously on these branches
Where is Glycogen stored
- In the muscles and in the liver
- In times of high energy usage, these organs hydrolyse the glycogen stored & break it down into glucose molecules which can be used in respiration
Size of Glycogen
- It is a relatively large but compact molecule thus maximising the amount of energy it can store.
- Makes it optimal for an energy storage molecule
Is Glycogen insoluble
Yes, being soluble means it will not affect the water potential of cells & cannot diffuse out of cells
see showbie slide 19 for diagram of Glycogen
What is the polysaccharide, Starch
- Starch is a mixture of 2 polysaccharides called amylose and amylopectin
- Both amylose and amylopectin are long-chain a-glucose polymers.
Main use of Starch
Starch is the main form of carbohydrate used for energy storage in plants
Where is Starch stored
Starch grains are stored in chloroplasts & are insoluble in water so they dont affect water potential up & down the xylem - important for water & nutrient transport in the plant
Starch is constructed from 2 different polysaccharides: AMYLOSE
- (10-30% of starch)
- long, unbranched, helix-shaped chain with 1,4 glycosidic bonds between a-glucsoe molecules.
- The helix shape enables it to be more compact & thus its more resistant to digestion
Starch is constructed from 2 different polysaccharides: AMYLOPECTIN
- (70-90% of starch)
- shorter, branched chains
- its branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily - meaning glucose can be released quickly
What is the polysaccharide, Cellulose
- Cellulose is a polysaccharide found in plants
- Unbranched, linear chains of B-glucose molecules which are joined by glycosidic bonds in a condensation reaction.
- It is a polymer of abt 10,000 B-glucose molecules in a long unbranched chain called a microfibril
Structure of Cellulose
- It consists of long chains of B-glucose, so in order to form the 1,4 glycosidic bonds consecutive B-glucose molecules must be rotated 180 to eachother
- Cellulose chains linked tg by hydrogen bonds to form strong fibres called microfibrils. The strong fibres mean cellulose provides structural support for cells
What are microfibrils
Strong threads which are made of long cellulose chains running parallel to one another that are joined tg by hydrogen bonds forming strong cross linkages
Function of Cellulose
Important in stopping the cell wall from bursting under osmotic pressure. This is bc it exerts inward pressure that stops the influx of water. This means that cells stay turgid & rigid, helping to maximise the SA of plants for photosynthesis
See slide 39 for diagrams of cellulose, amylose & amylopectin, and glycogen
What are carbohydrates made of
Most carbohydrates are polymers.
A polymer is a molecule made up of small monomers bonded tg.
The monomers that make up carbohydrates are called monosaccharides
How is starch adapted to be good for storage
Starch is INSOLUBLE in water, so doesnt cause water to enter cells by osmosis, which would make them swell, making them good for storage
Why is glycogen good for storage
Very compact molecules - so good for storage
