Biology AS Level Topic 1 Edexcel powerpoint

Biology
Unit 1…read more

Water
Substances can be transported more easily if they're dissolved
in a solvent. Water is a liquid and a solvent so it is very easy
to transport all sorts of materials (glucose and oxygen)
around plants and animals
Water is a dipolar molecule because:
· Each hydrogen atom has a slightly positive charge
· The unshared negative electrons on the oxygen atom give it
a slight negative charge
The negatively charged atoms of water attract the positively
charged hydrogen atoms of other water molecules. This
attraction is called hydrogen bonding.
Waters Dipolar nature makes it cohesive which helps water
flow, making it great for transporting substances.…read more

Carbohydrates
· Monosaccharides:
Glucose is a monosaccharide with 6 Carbon atoms in each molecule. There is alpha
glucose and beta glucose
Glucose is the main energy source in animals and plants It's structure makes it soluble so
it can be easily transported and it's chemical bonds contain lots of energy
Other monosaccharides are: Galactose and Fructose
· Disaccharides and Polysaccharides:
Monosaccharides are joined together by glycosidic bonds in a condensation
reaction.
When 2 monosaccharides join together they form a disaccharides.
· Maltose ( 2 glucose molecules)
· Lactose ( glucose and galactose)
· Sucrose ( Glucose and fructose)
A polysaccharide is formed when more than 2 monosaccharides join together.
· Amylose: lost of alpha glucose molecules joined together by 1-4 glycosidic bonds
· Amylopectin : alpha glucose with 1-4 and 1-6 glycosidic bonds
· Glycogen: alpha glucose with 1-4 and 1-6 glycosidic bonds…read more

Starch
· Starch is the main energy storage material in
plants
· Cells get energy from glucose but stores the
glucose as starch.
· Starch is a mixture of alpha-glucose, amylose
and amylopectin
· It is insoluble in water so it doesn't cause
water to enter cells by osmosis, making it
good for storage.…read more

Glycogen
· The main energy storage material in animals
· Animal cells get energy from glucose but they
store excess glucose as glycogen (another
polysaccharide of alpha glucose)
· It is a very compact molecule, so it's good for
storage
· It is also insoluble so it doesn't cause cells to swell
up from osmosis
· It is a large molecule so can store lots of energy…read more

Lipids
Triglycerides:
· Is made from 1 glycerol molecule and 3 fatty
acid molecules joined together by ester bonds
· Fatty acid molecules have long tails of
hydrocarbons
· The tails are hydrophobic so they are insoluble
in water…read more