Biology S6 Sem 1 Test 1

Elements that living organisms rely on

Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur

Why is carbon the basis for all biomolecules?

It allows four covalent bonds, able to form large and stable molecules of various shapes. Carbon forms the backbone of biomolecules

Monomers

A limited set of organic molecules which combine to form larger and complex molucules.

Polymers

Large and complex molecules made of monomers.

Why is water polar?

Water is a polar molecule because Oxygen is more electronegative than Hydrogen, causing the shared electron to lean closer to Oxygen

Polar nature of water

Allows water to interact with itself, other polar molecules, and with charged chemicals

Hydrogen bond

A weak bond between a partially-positive hydrogen and a partially-negative oxygen of different water molecules

Thermal properties of water

Water has a high heat of vaporisation, it takes a lot of energy to increase the temperature of water by 1°C. It is used in the process of sweating

Water has high specific heat, it makes water environments more stable in terms of temperature

Mechanical properties of water

• Cohesion: water molecule sticking to water molecules

• Adhesion: water molecule sticking to other molecules

Water density properties

Ice forms a lattice causing it to be less dense than liquid water

Water bodies freeze from top to bottom allowing organisms to survive

Chemical properties of water

Water is an excellent solvent for ionic polar chemicals. Water being the most abundant molecule in living organisms, it is important that certain chemicals can dissolve in it.

Hydrophilic

Any chemical able to interact/dissolve with water

Hydrophobic

Any chemical unable to interact/dissolve with water

Amphipathic

A chemical bearing hydrophilic and hydrophobic regions, e.g Phospholipids

Minerals

elements required for the proper functioning of cells, most of them under the form of ions associated to organic molecules or dissolve in water

Role of Carbohydrates

Source of energy, Storage of energy, Structure of the cell/organism, Signalling between cells or even inside cells, Precursors for the synthesis of other organic molecules

Monosaccarides

The building units of carbohydrates containing a carbonyl group and one or more hydroxyl groups

Two functional groups found in Monosaccharides

Carbonyl group, one or more hydroxyl group

Carbonyl Group, Ketone

Carbonyl Group, Aldehyde

Oligosaccarides

Few monosaccharides chemically linked (2 to 10)

Polysaccharides

Many monosaccharides linked together

Disaccharides

2 monosaccharides linked together (sucrose, maltose…)

Disaccharide formula

CnH2n-2On-1

Three of the most abundant polysaccharides

• Cellulose

• Glycogen

• Starch

  • Amylose

  • Amylopectin

Cellulose

long chains of β-glucose linked 1-4 That are linear and relatively straight. Multiple chains of cellulose can form microfibrils, binding through Hydrogen bonds Which is stiff and insoluble

2 main starch polysaccharides

• Amylose

• Amylopectin

Amylose

Chain of α-glucose linked 1-4, linear molecule with a coil

Amylopectin

Multiple amylose chains linked 1-6, branched molecule.

Glycogen

• Like starch but has increased rate of branching

• Store a large amount of glucose (>100000)

Fatty acids

Fatty acids are made up of carbon/hydrogen chains (hydrophobic) linked to a carbonyl group.

Saturated Fatty Acids

• Fatty acids that only contain carbon-carbon single bonds

• Generally solid at room temperature

Unsaturated Fatty Acids

• Fatty acids that contain one or more carbon=carbon double bonds

• Generally liquid at room temperature

Essential Fatty Acids

A family of unsaturated fatty acids which cannot be synthesised by mammals. ω3 and ω6 fatty acids are known to play a beneficial role in our health

Triglycerides

Fatty acids that are mainly stored to glycerol, forming triglycerides

Phospholipids

Phospholipids contain 2 fatty acids combined to a glycerol molecule, and a phosphate group linked to a polar/charged organic molecule

Phospholipids are amphipathic: It is able to form compartments like cells in a water environment as it has both hydrophilic and hydrophobic structures