Biological Molecules

Question 1

Within a water molecule, which atom has a slight negative charge and which has a slight positive charge? This causes it to be called a what molecule?

Answer 1

Oxygen has a slight negative charge and hydrogen has a slight positive charge, this causes it to be called a polar molecule.

Question 2

Why are water molecules attracted to each other?

Answer 2

Because of the hydrogen bonds that form between the oxygen atom to the hydrogen atom on the adjacent water molecule.

Question 3

What are the properties of water?

Answer 3

Thermal properties: high specific heat capacity, insulating (density).
Water as a solvent: metabolite in metabolic reactions hydrolysis and condensation.

Question 4

What does cohesion and adhesion mean in terms of water?

Answer 4

Adhesion: creates an attraction between water mols and surfaces.
Cohesion: property of water that creates an attraction between water mols.

Question 5

What is a condensation reaction?

Answer 5

A type of reaction involving the elimination of a water molecule that joins two molecules together forming a chemical bond.

Question 6

What is a hydrolysis reaction?

Answer 6

The breaking of a chemical bond between two molecules by adding a water molecule.

Question 7

What are the three types of saccharides and how are they joined together?

Answer 7

Monosaccharides, disaccharides and polysaccharides. They are joined together with glycosidic bonds formed in condensation reactions.

Question 8

Describe glucose as a carbohydrate.

Answer 8

A hexose monosaccharide containing 6 carbon atoms. Main substrate for respiration. C₆H₁₂O₆. Two isomers: alpha and beta. Diffuses easily and water soluble.

Question 9

What is the glycosidic bond between two alpha-glucose monomers called?

Answer 9

A 1,4-glycosidic bond because it forms between C1 of one glucose and C4 on the other.

Question 10

What disaccharide is formed by the condensation of two alpha-glucose molecules?

Answer 10

Maltose

Question 11

What disaccharide is formed by the condensation of one alpha-glucose and one fructose?

Answer 11

Sucrose

Question 12

What disaccharide is formed by the condensation of a glucose molecule and a galactose molecule?

Answer 12

Lactose

Question 13

What are polysaccharides?

Answer 13

Large polymers formed by many monosaccharides combining via condensation reactions to form either branched or unbranched long chains.

Question 14

What two molecules are formed by the condensation of alpha-glucose?

Answer 14

Glycogen and starch.

Question 15

What molecule is formed by the condensation of beta-glucose?

Answer 15

Cellulose.

Question 16

Describe the properties of glycogen.

Answer 16

Main energy storage in animals. Formed by many alpha-glucoses by 1,4 and 1,6 glycosidic bonds. Large number of side branches so glucose can be released quickly. Large but compact maximising volume of energy can store.

Question 17

Describe the properties of starch.

Answer 17

Mixture of two polysaccharides: amylose and amylopectin. Main energy store in plants.

Question 18

Describe the properties of amylose.

Answer 18

Unbranched chain of glucose molecules joined by 1,4 glycosidic bonds. Coiled and very compact so can store a lot of energy.

Question 19

Describe the properties of amylopectin.

Answer 19

Branched, made up of glucose mols joined by 1,4 and 1,6 glycosidic bonds. Many sided branches= rapidly digested so energy released quickly.

Question 20

Describe the properties of cellulose.

Answer 20

Component of cell walls in plants. Composed of long, unbranched chains of beta-glucose.

Question 21

Describe the properties of microfibrils.

Answer 21

Strong threads which are made of long cellulose chains joined together by hydrogen bonds. Provide structural support in plant cells.

Question 22

Describe the properties of lipids.

Answer 22

Macromolecules. Not polymers. Include: triglycerides (fats and oils), phospholipids, waxes and steroids (cholesterol). Hydrophobic and dissolve in organic solvents. Two types: saturated fatty acid and unsaturated fatty acid.

Question 23

Describe the properties of saturated fatty acids.

Answer 23

Fatty acid with a long hydrocarbon chain where none of the carbon atoms are linked with carbon-carbon double bonds. Each carbon atom is linked to two hydrogen atoms. Found in animal fats.

Question 24

Describe the properties of unsaturated fatty acids.

Answer 24

Fatty acid with long hydrocarbon chain with some double bonds between some carbon atoms. One hydrogen atom is bonded to each side of the carbon atom in the carbon-carbon double bond. Double bond changes the shape and causes a kink in the chain. Found in plants.

Question 25

Describe the properties of triglycerides.

Answer 25

Made of one glycerol mol and three fatty acids joined by ester bonds formed in condensation reactions. Can contain a mix of both fatty acid types or just one. Energy reserves in plant and animal cells.

Question 26

Describe the properties of phospholipids.

Answer 26

One of the fatty acids of a triglyceride is substituted for a phospho-containing group. Phosphate heads are hydrophilic and tails are hydrophobic creating micelles (circular formations) when in contact with water.

Question 27

What are the roles of lipids in living organisms?

Answer 27

Energy source= high energy yield when respired. Energy store= plants: lipid droplets animals: adipose tissue. Insulating layer= thermal insulation under skin of mammals + waxy cuticle around leaves & stems. Electrical insulator= some nerve cells. Biological membranes= made from lipids. Steroids= are lipids.

Question 28

Why are triglycerides efficient energy stores?

Answer 28

They are energy rich. Insoluble in water: they don't effect water potential of cell. When oxidised in respiration release H₂ which combine with O² forms metabolic water (desert animals rely on).

Question 29

Why is fat useful?

Answer 29

Insulator as poor conductor of heat. Aids buoyancy= useful in aquatic animals. Used as protection around vital organs.

Question 30

Describe the properties of cholesterol.

Answer 30

Contains hydrophilic and hydrophobic regions. Important part of cell membranes in eukaryotic cells. In vertebrates: made in liver, transported in blood. Used to make steroid-based hormones (testosterone, oestrogen and progesterone.)

Question 31

What are functions of proteins?

Answer 31

Cell growth, cell repair, replacement of materials. Some have structural roles: in cytoplasm, muscles, collagen, elastin in skin, keratin. Protein carrier molecules in cell membranes. Antibodies. Enzymes. Human hormones.

Question 32

Describe the properties of amino acids.

Answer 32

Monomers that form proteins. Contain amino/amine group (-NH₂), carboxyl group (-C00H) and variable R-group. Joined by peptide bonds formed in condensation reactions. Dipeptide contains two amino acids. Polypeptide contains three or more.

Question 33

What is the structure of proteins determined by?

Answer 33

Order and number of amino acids. Bonds present. Shape of protein.

Question 34

What are the different structures of proteins?

Answer 34

Primary structure. Secondary structure. Tertiary structure. Quaternary structure.

Question 35

Describe the primary structure of proteins.

Answer 35

Sequence, type and number of amino acids in a polypeptide chain. Position of disulphide bonds if present.

Question 36

Describe the secondary structure of proteins.

Answer 36

Polypeptide chain either folds or coils depending on bonds between amino acids. Two main forms: alpha helix and beta pleated sheet.

Question 37

Describe the alpha helix of the secondary structure of proteins.

Answer 37

Tightly coiled, polypeptide chain twists around itself. Held permanently in place by hydrogen bonds between amino acids.

Question 38

Describe the beta pleated sheet of the secondary structure of proteins.

Answer 38

Polypeptide chains folded with hydrogen bonds connecting to adjacent sheet.

Question 39

Describe the tertiary structure of proteins.

Answer 39

3D shape when secondary structure coils or twists further. Two main types: globular and fibrous.

Question 40

Describe the globular structure of the tertiary structure of proteins.

Answer 40

When protein folds and coils into a 3D shape. Enzymes: allows active site (amylase and catalase). Form protein-bases hormone, plasma proteins, antibodies and components of cytoskeleton.

Question 41

Describe the fibrous structure of the tertiary structure for proteins.

Answer 41

When protein twists into long structure. Important structural roles: keratin (hair &nails), collagen (skin, bone &cartilage) and fibrin (blood-clotting).

Question 42

What are the bonds in tertiary structure proteins?

Answer 42

Hydrogen bonds: large numbers stabilise, attraction between positive and negative R-groups. Ionic bonds: attraction between positive and negative R-groups. Disulphide bonds: covalent bond between sulphur atoms of R-group in 2 cysteine amino acids. Hydrophobic interaction between hydrophobic R-groups.

Question 43

Describe the quaternary structure of proteins.

Answer 43

When multiple polypeptide chains (subunits) interact and form a large, functional protein complex. Will not function unless all subunits are together. In some an inorganic mol or ion is also required.

Question 44

Describe the properties of haemoglobin.

Answer 44

Globular protein with quaternary structure. Haem group with an inorganic ion= prosthetic group= conjugated protein. Adult human haemoglobin: four polypeptide chains (2 alpha + 2 beta).

Question 45

What does a prosthetic group mean in terms of proteins?

Answer 45

Non-protein part that is permanently attached to protein and is vital for function.

Question 46

Describe the properties of insulin.

Answer 46

Globular protein produced by beta cells in Isle of Langerhans in pancreas. Two polypeptide chains. 21 amino acids in A, 30 in B held together by 3 disulphide bridges.

Question 47

Describe the properties of collagen.

Answer 47

Fibrous protein with quaternary structure. Three polypeptide chains twisted around each other. Many hydrogen bonds and covalent bonds between chains= provides strength. Forms collagen fibril links with other forms collagen fibre.

Question 48

What are key inorganic ions and their functions?

Answer 48

Hydrogen Ions (H⁺): determine pH, higher concentration of H⁺ lower pH. Iron ions: components of haemoglobin. Sodium ions (Na⁺): co-transport of glucose and amino acids. Phosphate ions: component of DNA and ATP