2.1.2c Carbohydrates Flashcards by Hyun J

Element composition of Carbohydrates

Carbon, Hydrogen, Oxygen

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Element composition of Lipids

Carbon, Hydrogen, Oxygen

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Element composition of Proteins

Carbon, Hydrogen, Oxygen, Nitrogen, Sulfur

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Element composition of Nucleic acids (DNA & RNA)

Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus

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What are monomers

Small units which are the components of larger molecules.

Eg. Monosaccharides sa glucose, amino acids & nucleotides

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What are polymers

Molecules made from many monomers joined together

Eg. starch, cellulose

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Process of monomers into polymers

Polymerization

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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

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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

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See showbie slide 5 to see diagrams of condensation & hydrolysis reactions

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What is the basic monomer in carbohydrates

Sugar, otherwise known as a saccharide

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What would a single monomer be called

Monosaccharides

mono = 1
O (hexagon)

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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

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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

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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

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How are polymers & disaccharides broken down into monomers

Hydrolysis reaction (breaking chemical bond using a water molecule)

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What are the bonds in carbohydrates

Glycosidic bonds

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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