Alevel bio - Biological Molecules

Importance of water having a High latent heat of vaporisation

Sweating acts as a cooling mechanism as high energy water molecules evaporate leaving the cooler water molecules behind

Importance of water having a high specific heat capacity

Hydrogen bonds absorb high amounts of energy preventing rapids swings in temperature in cells and aquatic habitats to prevent enzymes denaturing

Density of water as a solid (ice)

Ice more dense so floats and insulates water below ice allowing organisms to survive

Importance of Cohesion and surface tension in water molecules

Cohesion : Polar water molecules attracted to each other due to hydrogen bonds so a water column is created - pull water up xylem in plants

Surface Tension : Inward pulling forces at air-water interfaces creating a layer, skin like tension

Importances of water

• High Specific Heat Capacity

• High Latent Heat Of Vaporisation

• Density as a solid

• Dilutes Toxic substances - e.g urea

• Transport Medium - e.g sugars and amino acids in phloem or creating cohesive columns to pull up minerals

• Good Solvent

What bonds hold two monosaccharides to produce a disaccharide in a condensation reaction

Glycosidic bonds

Name examples of disaccharides and molecule breakdown

Maltose - 1 Glucose + 1 Glucose

Sucrose - 1 Glucose + 1 Fructose

Lactose - 1 Glucose + 1 Galactose

What are Monosaccarides?

Monomers of more complex carbohydrates

Properties of Monosaccarides

Soluble in water

Form Crystals

How is water a good transport medium/good solvent?

Polarity allows to dissolve many substances: Blood plasma carrying glucose and urea or Phloem dissolving sugars to be transported in plants

Water Polarity

Electrons not equally distributed through bonds due to oxygen being more electronegative so the oxygen atom is slightly more negative and the two hydrogen atoms slightly more positive

Glycogen

-Polysaccharide

-Main form of energy for animals

-Made up of lots of alpha glucose molecules

-Lots of side branches allowing rapid energy release.

- Molecule is large but compact to maximise energy storage

Examples of polysaccharides

Glycogen

Starch

Cellulose

Starch

Stores energy in plants

Mix of two polysaccharides - amylose and amylopectin

Starch can be quickly converted to glucose for respiration

Amylose

Component of Starch

Polysaccharide

Unbranched chain of glucose molecules with 1,4 glycosidic bonds

Compact and can coil up to maximise energy storage

Amylopectin

Component of starch

Polysaccharide

Has many side branches with 1,4 glycosidic bonds

Branches have 1,6 glycosidic bonds so glucose can be released at a faster rate

Cellulose

Constructed of many beta glucose molecules

Every other beta molecule flipped 180 degrees so OH groups match and a 1,4 glycosidic bond is formed

Component of cell walls in plant cells

Microfibrils

Strong threads made of long cellulose chains joined by hydrogen bonds