biological molecules

Question 1

Nutrients

Answer 1

Chemical substances in food that provide energy and minerals needed by the body

Question 2

Biological molecules

Answer 2

Molecules of life-critically important molecules needed for organisms to survive
Three dimensional molecules which contain carbon atoms arranged in rings or chains - organic molecules

Question 3

Condensation reaction

Answer 3

Condensation reaction is a chemical reaction whereby two or more simple molecules are joined together to form a larger biological molecule with the removal of water

Question 4

Hydrolysis

Answer 4

Hydrolysis is the splitting up of a complex biological molecule into its components with the addition of water molecules

Question 5

Carbohydrates

Answer 5

Carbohydrates are made up of the elements carbon, hydrogen and oxygen.
The hydrogen and oxygen atoms are present in the ratio 2:1

Question 6

Monosaccharides

Answer 6

Simplest form of carbohydrates - cannot be hydrolysed further into simpler units.
Most common monosaccharide are sugars with six carbon atoms: glucose, fructose, and galactose.
Same general formula C6H12O6, but atoms are arranged differently within the molecules, resulting in different chemical and biological properties.

Question 7

Common properties of monosaccharides

Answer 7

Generally sweet-tasting
Soluble in water
Able to lower water potential of solutions

Question 8

Disaccharides

Answer 8

Disaccharides are made up of two monosaccharides through condensation reaction.
The bond formed between monosaccharides is called glycosidic bond, which is a covalent bond.
Common types of disaccharides: maltose, lactose and sucrose
Same general formula C12H22O11, but the different structure and properties, due to different building units and they way they are bonded.

Question 9

Building units of common disaccharides

Answer 9

Maltose - glucose and glucose
Lactose - glucose and galactose
Sucrose - glucose and fructose

Question 10

Polysaccharides

Answer 10

Consists of many monosaccharides joined together through condensation reaction to form one polysaccharide.
They have glycosidic bond between monosaccharides.
Common types of polysaccharides include storage polysaccharides (starch and glycogen) and structural polysaccharides (cellulose).
Starch, glycogen and cellulose are comprised entirely of glucose, but their properties are different, due to the different ways in which the glucose units are linked together

Question 11

Starch

Answer 11

Found in plants.
Formed from the condensation reaction of large numbers of glucose meolecules.
Starch can be in long straight chains (amylose) or branched chains (amylopectin).

Question 12

Glycogen

Answer 12

Found mainly in animals.
Formed from the condensation reaction of large numbers of glucose molecules.
The glucose molecules are joined up in highly branched chains.
It is mainly stored in the liver and muscles of mammals.

Question 13

Properties of starch and glycogen

Answer 13

They are insoluble in water so they do not affect the water potential in cells.
They are too large to diffuse through the cell membranes, so they stay in the cells.
They have compact shapes which occupy lesser space than all the individual glucose molecules that make up a glycogen or starch molecule.
They can be easily hydrolysed to glucose when needed.

Question 14

Cellulose

Answer 14

Structural polysaccharides.
Formed from the condensation reaction of large numbers of glucose molecules.
Glucose molecules that form cellulose are bonded differently as compared to starch, hence giving cellulose a different property.
Insoluble in water.

Question 15

Cellulose cell wall

Answer 15

Consists of cellulose fibres embedded in a polysaccharide matrix.
Fully permeable structure.
Functions: to provide mechanical support for plant cell and to the plant, especially for soft stem plants. To resist expansion when water enters by osmosis, ensuring integrity of plant cell and to provide turgidity.

Question 16

General functions of carbohydrates

Answer 16

Glucose - as a substrate for respiration, to release energy for all cell activities
Ribose sugar - used for the formation of nucleic acids (eg DNA)
Forms lubricants (eg mucus)
Forms nectar in some flowers
Cellulose - to form supporting structure (eg cell walls)

Question 17

Lipids

Answer 17

Lipids are organic compounds containing carbon, hydrogen and oxygen, with much lesser oxygen as compared to carbon and hydrogen
Lipids are insoluble in water but soluble in organic solvents such as alcohol

Question 18

Simple lipids- triglycerides

Answer 18

Triglyceride consists of three molecules of fatty acids and one molecule of glycerol

Question 19

Fatty acid

Answer 19

A fatty acid is a long hydrocarbon chain that has a carboxyl functional group- COOH
The hydrocarbon chain can be unsaturated (contain one or more carbon-carbon double chain, C=C) or saturated (lack of carbon-carbon double bonds)
Hydrophobic

Question 20

Glycerol

Answer 20

Glycerol is an alcohol
Formula: C3H8O3

Question 21

Formation of triglyceride

Answer 21

Formation of one molecule of triglyceride by condensation reaction of 3 molecules of fatty acids and 1 molecule of glycerol with the removal of 3 molecules of water.
The three fatty acids can be the same or different.
Bond formed between 1 fatty acid and glycerol is an ester bond.

Question 22

Properties of triglycerides- oil

Answer 22

*classified as fats or oils, depending on their state: solids (fats) or liquids (oils) at rtp
Oil (triglycerides with unsaturated fatty acids)
Presence of at least one carbon-carbon double bond between carbon atoms and has relatively shorter fatty acid chains.
Lower melting point and molecular weight.

Question 23

Properties of triglycerides- fats

Answer 23

Fats (triglycerides with saturated fatty acids)
Absence of carbon-carbon double bonds and relatively longer fatty acid chains
Higher melting point and molecular weight

Question 24

Properties of triglycerides- compact and insoluble in water

Answer 24

Insoluble in water.
Fats are stored as droplets inside specialized fat cells, known as adipose cells, because they are insoluble and do not affect water potential in cells.

Question 25

Functions of triglycerides - energy storage

Answer 25

Triglyceride contains a greater number of carbon-hydrogen bond per gram than starch or glycogen, therefore, one gram of triglyceride yields about twice as much energy than one gram of carbohydrates.
Triglyceride has about half the mass of carbohydrates for an equivalent amount of energy stored.
It is therefore a lightweight energy source for animals that move by speed or flight and seeds dispersed by wind or insects.
*carbohydrates are still the most utilized energy source as they are mobilized quickly

Question 26

Functions of triglycerides - heat insulator

Answer 26

Fats conduct heat slowly. Excellent heat insulator against heat loss from deeper regions of the body to the outside.

Question 27

Functions of triglycerides - buoyancy in aquatic mammals

Answer 27

Less dense than water

Question 28

Functions of triglycerides - protective layer

Answer 28

Ability to absorb shock

Question 29

Functions of triglycerides - important component to myelin sheath

Answer 29

Act as electrical insulator, allowing rapid transmission of electrical impulses along myelinated neuroses.

Question 30

Functions of triglycerides - provides metabolic water

Answer 30

Oxidation of triglycerides produces metabolic water.
Triglycerides release twice as much water as carbohydrates when oxidized during respiration.
Water produced from respiration is known as metabolic water.
The hydrogen atoms of triglycerides and carbohydrates are used in the formation of metabolic water during oxidation.
Triglycerides contain more hydrogen atoms than carbohydrates, so it is a better source of metabolic water.

Question 31

Functions of triglycerides - as a solvent

Answer 31

A solvent for fat-soluble vitamins and other vital substances.

Question 32

Structure of phospholipids

Answer 32

Phospholipids are a group compound lipids that contain two molecules of fatty acids, one molecule of glycerol and a phosphate group.
Phospholipids has a hydrophilic and a hydrophobic component - the phosphate group is hydrophilic and the fatty acid tails are hydrophobic

Question 33

Phospholipids- phosphate group and fatty acid tails

Answer 33

The hydrophilic phosphate group is attracted to the water molecules in their environment and the hydrophobic fatty acid tails are repelled by the water molecules, the hydrophilic heads face the aqueous environment while the hydrophobic tails face the inside of the bilayer, away from water in their environment forming the interior of the membrane.

Question 34

Functions of phospholipids

Answer 34

Phospholipids are a major component of biological membranes. Due to the nature of phospholipids, the cell membrane is made up of two layers of phospholipids - phospholipid bilayer.

Question 35

Proteins

Answer 35

Protein are made up of the elements carbon, hydrogen, oxygen and nitrogen. Sulfur is sometimes present.
Each type of protein has a unique 3D shape thus proteins have diverse functions.
When heated, the weak bonds in protein are broken, the protein is denatured.
Proteins are polymers made up of monomers- amino acids

Question 36

Amino acids

Answer 36

Monomers (building units) of the protein.
There are 20 naturally occurring amino acids.
Every amino acid molecule has a central carbon atom bonded covalently.
Different amino acids have different R groups- gives different properties and functions.

Question 37

Formation of polypeptide

Answer 37

Amino acids join together to form polypeptide through condensation reaction with the removal of water molecules.
The covalent bond that is formed is a peptide bond.
Continued condensation reaction result in the formation of a long chain of amino acids- polypeptide.
Conversely, hydrolysis can break down peptide bonds of polypeptides into amino acids with the addition of water molecules.

Question 38

Bonds in protein structure

Answer 38

Peptide bonds join the amino acids to form a polypeptide chain
The polypeptide chain fold into a particular 3D shape as a result of four other types of bonds (disulfide bonds, ionic bonds, hydrogen bonds, and hydrophobic interactions).

Question 39

Functions of proteins

Answer 39

Used in the synthesis of new cells, for growth and repair of worn up cells.
Biological catalysts- enzymes, to speed up chemical reactions.
Chemical messenger- hormones such as insulin
Transport proteins- such as haemoglobin which transport oxygen in red blood cells
Structural protein - such as collagen which is a component of skin and bones while keratin is a component of hair and nails
Defence of body- antibodies used to help fight infections in the body
Source of energy during starvation and is oxidised after all the carbohydrates and lipids are used up.