Molecular biology

Name the properties of water

Cohesive, Adhesive, Thermal, Solvent

Why is water solvent?

Due to polarity, water molecules can separate other polar molecules easily

Why does water have the property of cohesion?

It is due to hydrogen bonds forming between water molecules as a result of polarity (i.e. weak forces of attraction of oxygen and hydrogen atoms)

Why does water have the property of adhesion?

It is due to dipolarity, molecules adhere to polar to hydrophillic surfaces (i.e. atoms in xylem)

What are the thermal properties of water?

High specific heat capacity

Why does water have these thermal properties?

Due to STRONG hydrogen bonds, water has high melting and boiling point

What are the benefits of water having a high specific heat capacity?

It remains a constant temperature, fluctuating very little from the mean. This means, that it makes a good habitat for organisms that reside within the sea, ocean or rivers

What are the benefits of water having a high latent heat of vaporization?

It makes a good coolant, as vaporization allows heat to be taken away from body in sweat

What is an example of cohesion benefiting an organism?

Pulling forces can allow water to be transported to areas of a tree above the ground, through the xylem

What is an example of adhesion benefiting an organism?

Adhesive force between water and cellulose wall allows water to be transported from xylem to cell to keep cell wall moist and primed for gas exchange (also applicable to alveoli)

What is an example of the solvent properties of water benefiting an organism?

It allows for blood withing animals to act as a medium of transportation.

Which substances are carried by their blood, and how?

NaCl, ionic compound so dissolves easily into plasma as ions Na and Cl

Glucose and amino acids are polar so water molecules can easily break weak intramolecular molecular forces them to be dissolved in the plasma

Oxygen is non-polar, so must be combined with hemoglobin in erythrocytes to be transported

Metabolism

web of all enzyme-catalysed reactions in a cell or organism

Where does metabolism occur?

Cytoplasm, mitochondria, choloplasts

Anabolism

synthesis of polymers from monomers

Catabolism

breaking down of polymers to form monomers

Hydrolysis reaction

E.g. two amino acids form a dipeptide, linked by a peptide bond and one molecule of water

Condensation reaction

E.g. The peptide bond breaks in a dipeptide and an OH and H atoms saturate bonds forming two amino acids

Polypeptide

amino acid

Polysaccharide

monosaccharide (carbohydrate)

lipids

monoglycerides and fatty acids

nucleic acid

nucleotides

Urea

nitrogenous waste produced by break down of polypeptides

What is significant about urea?

It was synthesized in a laboratory falsifying the theory of Vitalism, instead suggesting organic molecules did not have a 'vital force' and instead are not fundamentally different to inorganic molecules

How do the cohesive properties of water explain its surface tension?

The hydrogen bonding between water molecules allows the liquid to resist low levels of external force (surface tension)

The high surface tension of water makes it sufficiently dense for certain smaller organisms to move along its surface

How do the adhesive properties of water explain capillary action?

Attraction to charged or polar surfaces (e.g. glass) allows water to flow in opposition of gravitational forces (capillary action)

This capillary action is necessary to allow water to be transported up plant stems via a transpiration stream

Organic compound

a compound that contains carbon and is found in living things

Why is carbon the basis for organic life?

it can form four covalent bonds allowing a diversity of stable compounds to exist

What are the main classes of carbon compounds?

Carbohydrates, lipids, nucleic acids, proteins

What is a carbohydrate composed of?

C,H and O atoms in a common ratio - (CH2O)n

What is a lipid?

Non-polar, hydrophobic molecule comes in variety of forms - simple, complex or derived

What is the function of carbohydrates?

a source of energy (and as a short-term energy storage option) and also as

a recognition molecule (glycoproteins) and as

a structural component (part of DNA / RNA)

What is the function of lipids?

component of cell membrane (phospholipid, cholestrol)

long term energy store (fats, oils)

signalling molecule

What is a nucleic acid?

DNA and RNA

What is the function of nucleic acids?

To form genetic material, DNA - master code for protein assembly, RNA - manufactures protein

Proteins are composed of which atoms?

C, H, O, N

What is the role of proteins?

Major regulatory molecules involved in catalysis (enzymes)

structural molecules

role in cellular signalling

Describe the structure of an amino acid

Amine: NH2

Carboxyl: COOH

Variable R group

Hydrogen atom: H

Describe the structure of a nucleotide

Phosphate group: 3(O)-P=O

Pentose sugar

Nitrogenous base

How are glycerol and fatty acids joined to make triglycerides?

ester linkages

How are monosaccharides joined to form polysaccharides?

glycosidic linkages

How are amino acids joined to form polypeptide chains?

peptide bonds

How are nucleotides joined to form polynucleotide chains?

phosphodiester bonds

What are the polymers of glucose?

glycogen, cellulose and starch

Name two reasons for metabolism

They provide a source of energy for cellular processes (growth, reproduction, etc.)

They enable the synthesis and assimilation of new materials for use within the cell

Name three examples of monosaccharides

glucose, galactose, fructose

Name three examples of disaccharides

lactose, maltose and sucrose

Name three examples of polysaccharides

cellulose, glycogen and starch

What is the function of monosaccharides?

immediate energy source

What is the function of disaccharides?

transport

What is the function of polysaccharides?

long-term energy store, cell structure or cell recognition

What is the structure of cellulose?

linear molecule composed of β-glucose subunits (bound in a 1-4 arrangement)

What is the function of cellulose?

structural polysaccharide found in cell wall of plants, cannot easily be digested by most animals due to lacking specific enzyme

What is the structure of starch?

energy storage composed of α-glucose subunits (bound in a 1-4 arrangement) exists in one of two forms - amylose or amylopectin

Distinguish between amylose and amylopectin in terms of structure and function.

Amylose - linear (helical) molecule: harder to digest and less soluble but takes up less space (preferred storage form in plants)

Amylopectin - branched (contains additional 1-6 linkages)

What is the structure of glycogen?

energy store composed of α-glucose subunits linked together by both 1-4 linkages and 1-6 linkages (branching)

It is similar to amylopectin, but more highly branched (every 20 compared to 10)

Fatty acids that possess no double bonds are...

saturated

Fatty acids with double bonds are...

unsaturated

Structure of unsaturated fatty acids

Bent (double bond)

Structure of saturated fatty acids

Linear

Types of fatty acid

saturated, monounsaturated (one double bond), polyunsaturated (several double bonds)

Distinguish between cis and trans unsaturated isomers

Cis: The hydrogen atoms attached to the carbon double bond are on the same side

Trans: The hydrogen atoms attached to the carbon double bond are on different sides

Which isomer of unsaturated fatty acid is not naturally occurring?

Trans, produced by industrial process of hydrogenation to maintain linear structure and thus remains solid at room temperature