biological molecules

Why is water a polar molecule

Oxygen has a small negative charge and hydrogen has a small positive charge

What is a hydrogen bond

Water molecules are attracted to each other due to being polar molecules

What are the six properties of water

• high specific heat capacity

• Ice less dense than water

• High latent heat of vapourisation

• Cohesion

• Metabolite

Why is water having a high specific heat capacity beneficial

Lots of heat energy goes into breaking bonds rather than changing temperature so water acts as a buffer so it can act as a habitat

Why is ice being less dense than water beneficial

It provides a habitat and insulates the water below and keep it from freezing

Why is having a high latent heat of vaporisation beneficial

A large amount of heat needed to evaporate water which allows organisms to cool without much water

Why is water being a solvent beneficial

For chemical reactions and to transport substances as they easily dissolve via blood plasma or xylem tubes

Why is cohesion beneficial

It is caused by hydrogen bonds and it allows water to travel up narrow tubes and causes surface tension to allow small organisms to survive on surface

Why is water being a metabolite beneficial

It’s essential for metabolic reactions such as respiration and photosynthesis

What do all carbohydrates consist of

Carbon, hydrogen and oxygen e.g. C6H12O6

Wat is glucose since it contains 6 carbons

A heroes sugar

What is the general formula for monosaccharides

(CH2O)n where n is 3-7

What is the diagram for glucose

What are the three examples of monosaccharides

Glucose, fructose and galactose

What is a property of monosaccharides

They are soluble in water as they have a large number of hydroxyl groups which can form hydrogen bonds with water molecules so they are hydrophilic

What are the two isomers of glucose

Alpha and beta glucose

What is the structure of beta glucose

What is the difference between alpha and beta glucose

In alpha glucose, the OH group is below the carbon-1 but in beta glucose, the OH group is above the carbon 1 (ABBA)

What forms a disaccharide

When two monosaccharides chemically react together

Examples of disaccharides

• Glucose + glucose = maltose

• Glucose + galactose = lactose

• Glucose + fructose = sucrose

What happens when two glucose form maltose

A condensation reaction takes place as water is produced from a hydrogen atom from one and hydroxyl group from another and a glycosidic bond is formed

What is a hydrolysis reaction

Adding water to disaccharides breaks the glycosidic bond, converting them back to monosaccharides

What is starch

A storage polysaccharide found in plants

Why is storing glucose in its form hard

It’s extremely soluble due to the hydroxyl groups as it is polar so they can form hydrogen bonds with water so it makes water move into cells by osmosis

How does starch fix glucose inability to store problem

It is insoluble

What are the two types of starch

Amylose and amylopectin

What is amylose

Polymer of a-glucose and it twists into a compact helix with hydrogen bonds forming along glucose molecules

What is amylopectin

Polymer of a-glucose with a branch every 25-39 glucose connecting to another glucose chain via a 1-6 glycosidic bond

Why does amylopectins structure benefit it

It is heavily branched so has lots of ends so it leads to a faster breakdown via amylase which breaks down starch by acting at the ends of molecules

How is starch broken down back into glucose

By water via a hydrolysis reaction which breaks the glycosidic bond

What are the properties of starch (3)

• compact = large amount of glucose stored

• Insoluble = doesn’t cause water to enter cells

• Polymer = too large to diffuse out

What is glycogen

Storage polysaccharide in animals found in liver and muscle cells

What is glycogens structure

Polymer of a-glucose arranged like amylopectin but more branched so is more compact

Why must glycogen have a lot of branches

To convert back to glucose rapidly which is essential for animals due to a high rate of respiration

What are the properties of glycogen

• highly branched

• Insoluble

• Large

What is cellulose

Structural polysaccharide found in cell wal

What is celluloses structure

Polymer of b-glucose but since the hydroxyl groups is above carbon 1, every 2nd carbon flips so it can still form a 1-4 glycosidic bond

How are cellulose fibres formed

Since cellulose is a straight chain, hydrogen bonds form with neighbouring chains which are strong due to the sheer amount which form micro fibrils which group to form microfibrils then fibres

What is the features of the cellulose cell wall

• strong so provides structural support

• Permeable so molecules can enter such as water which causes the cell content to be pushed outwards, preventing it from bursting