Edexcel Biology As level
unit one
- Created by: Summer
- Created on: 04-05-11 20:28
what is meant by a dipolar molecule?
A dipolar molecule has a negavite charge on one side and a positive charge on the other.
What is cohesion?
-Dipole nature makes it very cohesive
-Cohesion attraction is the attraction between molecules of the same type.
-Water molecules are very cohesive (they tend to stick together) because they are dipolar.
-cohesion of water molecules helps water flow, making it great for transporting substances.
Describe the structure of a water molecule
-Water molecules have two hydrogen atoms and one oxygen atom.
-The hydrogen and oxgyen are joined by shared electrons.
(diagram)
What are the physical characteristics of water tha
-Water makes up to 80% of a cell contents.
-Water is a solvent, which means some substances dissolve in it. (most biological reactions take place in a solution=water essential)
-Water transports substances. Substances can be transported more eaily if they are dissolved in a solvent. Water is a solvent and a liquid.
(oxygen and glucose are able to get around plants and animals by this)
Why does water's dipole nature make it useful as a
-because water is dipolar, the postive end of a water molecule will be attracted to the negative ion, and the negative end of the water molecule will be attracted to the positive ion.
-This means the ions will get totally surrounded by water molecules- in other words they dissolve.
Relate the structure of water to it's ablity to tr
-in a water molecule, the shared electrons are pulled down closed to the oxygen atom than the hydrogen atoms.
-this makes the molecule dipolar, which makes water a good dolvent for other dipolar molecules.
-substances can be transported in a solvent like water.
-water is also cohesive due to its polar nature.
-this helps water to flow, which means it can transport substances.
What are carbohydrates?
- Carbohydrates are a main energy supply in living organisms.
-most carbohydrates are large, complex molecules composed of long chains of MONOSACCHARIDES,
-(e.g. starch is a large carbohydrate composed of long chains of glucose)
-single monosaccharides are also called carbohydrates.
-glucose is a monosaccharide with 6 carbon atoms in each molecule.
- carbohydrates are the main energy source in animals & plants because it is soluble, therefor eit is easily transported. The chemical bonds contain losts of energy,
What are two types of glucose?
-Alpha glucose
-Beta glucose
Monosaccharides join together to form what?
-Disaccharides
-Polysaccharides
Monosaccharides are joined together by glycosidic
-A condensation reaction
(a reaction where a molcule of water is released)
-A hydrogen atom on one monosaccharide bonds to a hydroxyl (OH) group on the other, releasing a molecule of water.
What is the reverse of a condensation reaction?
-A hydrolysis reaction
-A molecule of water reacts with the glycosidic bond breaking it apart.
How are disaccharides (sucrose, lactose and maltos
-When two monosaccharides join together, they form a disaccharide.
-Two alpha glucose molecules are joined together by a glycosidic bond to form maltose.
-Glycosic bonds can form in different places in different molecules.
-In maltose the bonds form between the carbon 1 of the first monosaccharide and the carbon 4 of the second (1-4 glycodsic bond)
-Lactose- beta glucose and galactose. 1-4 glycoidsic bond.
-Sucrose-alpha glucose and frutose. 1-2 glycosidic bond.
Name the two monosaccharides that join together to
-beta glucose and galactose
How is a polysaccharide formed?
-When more than two monosaccharides join together.
Lots of alpha molecules are joined together by 1-4
Amylopectin: beta glucose with 1-4 and 1-6 glycosidic bonds, with lots of side brances.
Glycogen: alpha glucose with 1-4 and 1-6 glycosidic bonds and even more side brances than amylopectin.
Name the two monosaccharides that join together to
-beta glucose and galactose
Two polysaccharides- what is the function of starc
- starch is the main energy storage material in plants.
How is a polysaccharide formed?
-When more than two monosaccharides join together.
Lots of alpha molecules are joined together by 1-4
Amylopectin: beta glucose with 1-4 and 1-6 glycosidic bonds, with lots of side brances.
Glycogen: alpha glucose with 1-4 and 1-6 glycosidic bonds and even more side brances than amylopectin.
Two polysaccharides- what is the function of starc
- starch is the main energy storage material in plants.
Where do cells get energy?
-Cells get energy from glucose.
-Plants store excess glucose as starch when a plant needs more glucose for energy it breaks down starch to release the glucose.
Starch is a mixture of what two polysaccharides of
-Amylose
-Amylopectin
Describe Amylose-Structure
-long unbranched chain of glucose joined together with 1-4 glycosidic bonds.
-the angle of the glycosidic bonds give it a coiled structure- (almost like a cylinder)
-Making it compact and good for storage----fit more in a small space.
Describe Amylopectin-Structure
-a long branched chain of glucose that contains 1-4 and 1-6 gllycosidic bonds.
-its side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily---glucose can be released quickly.
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