IB biology: topic 2: molecular biology

what regulate biological processes?

enzymes

what are signalling molecules?

molecules that changes activity of enzymes

what is an organic compound?

an organic compound is a compound that contains carbon and is found in living things

why is carbon the basis of organic life?

due to its ability to form complex molecules via covalent bonding - can form four covalent bonds - organic compounds are stable

what are four principle groups of organic compounds?

• carbohydrates

• proteins

• lipids

• nucleic acids

outline carbohydrates

• source of energy + short term energy storage.

• recognition molecule (e.g. glycoproteins) and as a structural component (part of DNA / RNA).

outline proteins

• major regulatory molecules involved in catalysis (all enzymes are proteins).

• structural molecules + play a role in cellular signalling.

outline nucleic acids

• genetic material of all cells + determines inherited features.

• DNA code for protein assembly.

• RNA manufacturing of proteins.

outline lipids

• non-polar, hydrophobic molecules.

• major component of cell membranes - (phospholipids and cholesterol).

• long-term energy storage molecule (fats and oils).

• signalling molecule (steroids).

what key organic compounds ARE polymers?

carbohydrates + proteins + nucleic acids

what key organic compounds ARE NOT polymers?

lipids only

what is the monomer of carbohydrates?

monosaccharides:

made up of ring structure, pentose = 5 carbonds, hexose (glucose) = 6 carbons

what is the monomer of nucleic acids?

nucleotides:

• Each nucleotide consists of 3 components – a pentose sugar, a phosphate group and a nitrogenous base.

• The type of sugar and composition of bases differs between DNA and RNA.wha

what is the monomer of proteins?

amino acids:

• Each amino acid consists of a central carbon connected to an amine group (NH₂) and an opposing carboxyl group (COOH).

• A variable group gives different amino acids different properties (e.g. may be polar or non-polar, etc.).

what are different types of lipids?

triglyceride, phospholipid and steroid.

what are the 3 main classes of lipids?

• simple lipids – fatty acids and alcohol (e.g. triglycerides).

• compound lipids – fatty acids, alcohol + other (e.g. phospholipids and glycolipids).

• derived lipids – substances derived from simple or compound lipids (e.g. steroids).

what are examples of different carbohydrate polymeres?

glycogen (granules), cellulose (cell walls) and starch (granules)

how are monosaccharides linked together to form polysaccharides?

glycosidic linkages

how are glycerol and fatty acids linked together to from triglycerides?

ester linkage

how are protein polymers made?

• amino acids join together by peptide bonds - form between amine + carboxyl groups.

• fusion of two amino acids creates dipeptide, further additions resulting in polypeptide chain.

• subsequent folding of chain depends on the order of amino acids in a sequence (based on chemical properties).

how do nucleotide monomers react together? what polymer do they form?

• nucleotides form bonds between pentose sugar and phosphate group to form long polynucleotide chains,

• each nucleotide is joined by phosphodiester bonds.

• in DNA, two complementary chains will pair up via hydrogen bonding between nitrogenous bases to form double strands -twist into double helix.

what was vitalism? how was it disproved?

• belief that organic molecules could only be synthesised by living system with “vital force”

• disproved by Frederick Woehler who artificially produced urea.

what is metabolism?

the totality of chemical processes that occur within a living organism in order to maintain life

what are the functions of metabolic reactions?

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

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

what are anabolic reactions?

the build up of complex molecules from simpler ones - occurs via condensation - endothermic

what are catabolic reactions?

the break down of complex molecules down into simpler molecules - occurs via hydrolysis - exothermic

what are condensation reactions?

monomers are covalently joined and water is produced as a by-product