Edexcel Biology As level

unit one

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  • 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.

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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.

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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)

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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)

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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.

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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.

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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,

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What are two types of glucose?

-Alpha glucose

-Beta glucose

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Monosaccharides join together to form what?

-Disaccharides

-Polysaccharides

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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.

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What is the reverse of a condensation reaction?

-A hydrolysis reaction

-A molecule of water reacts with the glycosidic bond breaking it apart.

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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.

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Name the two monosaccharides that join together to

-beta glucose and galactose

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How is a polysaccharide formed?

-When more than two monosaccharides join together.

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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.

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Name the two monosaccharides that join together to

-beta glucose and galactose

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Two polysaccharides- what is the function of starc

- starch is the main energy storage material in plants.

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How is a polysaccharide formed?

-When more than two monosaccharides join together.

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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.

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Two polysaccharides- what is the function of starc

- starch is the main energy storage material in plants.

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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.

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Starch is a mixture of what two polysaccharides of

-Amylose

-Amylopectin

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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.

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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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