What are the four main biological compounds in a cell?
- Lipids (fatty acids, fat and phospholipids)
- Carbohydrates (sugars and polysaccharides)
- Nucleic acid and nucleotides
- Proteins, peptides and amino acids
Define lipids
Soluble in non-polar solvents e.g. benzene - practically insoluble in water
LIPIDS: Define fatty acids
- Fatty Acids - carboxylic acids (COOH group)
=> saturated fatty acid- C-C single bonds e.g. stearic acid
=> unsaturated fatty acid - saturated(single C bond) replaced by double C bond e.g. oleic acid
=> hydrophobic - hydrocarbon chain, hydrophilic - carboxyl group
=> when placed at air-water interface, monolayer formed =polar carboxyl in contact with water, nonpolar hydrocarbon tail faces away from water
LIPIDS: Define micelles
- lipid low water solubility
- Conc > solubility limit = micelles spontaneously formed (spherical)
- Micelle structure - hydrophilic end contacts water, hydrophobic ends close together to minimise water contact
LIPIDS: Define fats
Esters formed by condensation of fatty acids with glycerol
=> broken down by fat-splitting enzymes in digestive system
LIPIDS: Define phosphoglycerides and describe their shared properties with a part of the cell.
Similar in structure to fat but different in functions
=> phosphate molecule replacing one of fatty acid branch in fat molecule
=> form lipid bilayers = properties shared with cell membrane - high electrical resistance and capacitance, cell walls of viable organisms become leaky when mild heat/chemicals applied
LIPIDS: Define fat-soluble vitamins
Organic substances, necessary for normal cell function
=> fat soluble are lipids = e.g. vitamin A,E etc. - insoluble in water but dissolve inorganic solvents
=> water soluble vitamins not lipids- e.g. vitamin C
Define carbohydrates and its functions. What is the general formula?
· Organic compounds found in plant, animal cells
- General formula = (CH_2 O)_n
Functions - energy source(sugars), energy storage and structural purposes (polysaccharides)
CARBOHYDRATES: Define monosaccharides
- Smallest carbohydrate (3-9 carbons)
- 2 types - ALDOSES (aldehyde group e.g. glucose), KETOSES (ketone group e.g. fructose)
- D-glucose = most common, ring structure, biologically active
CARBOHYDRATES: Define disaccharides
- Disaccharides - formed when aldehyde/ketone group from one monosaccharide reacts with hydroxyl group from another, water molecule removed (condensation reaction)
- Oligosaccharides - short chain of repeating monosaccharides
Polysaccharides - long chain of repeating monosaccharides or disaccharides
CARBOHYDRATES: What is cellulose?
Most abundant organic compound on earth, water insoluble. Crystalline structure from hydrogen bonding
Define nucleic acids
· DNA (deoxyribonucleic acid) and RNA(ribonucleic acid)
- Polymers made up of subunits called nucleotides
What is the structure of nucleotides?
- Phosphoric acid
- Five carbon sugars
- Nitrogen base
What are the nitrogen base pairs in DNA and RNA?
DNA
- Adanine and Thymine (A&T)
- Cytosine & Guaninane (C&G)
RNA
- Adanine and Uracil (A&U)
- Cytosine & Guaninane (C&G)
Describe the function of DNA
· DNA function - nucleus contains most DNA carrying hereditary info
=>plasmids manipulated and the recombinant plasmids are introduced into living cells
=> function of DNA - store RNA molecule synthesis instructions with specific length and nucleotide sequences, then involved in variety of protein synthesis , gene - segment of DNA coding for RNA molecule sequence
Describe the function of RNA
RNA - reading and implementing genetic instructions of DNA, single stranded
=> messenger RNA(mRNA) - carries info about protein sequence to ribosomes
=> ribosomal RNA (rRNA) - forms up to 65% of ribosomes
=> transfer RNA (tRNA) - smallest (70-95 nucleotides)
Define proteins.
· Large biopolymers - roles include: contribute to cell membrane structure, motive functions
· Formed from group of 20 amino acids (long chain)
· Simple proteins formed by condensation of amino acids
Polypeptides - short condensation chains of amino acids
What is the structure of a protein?
- Primary - particular sequence of amino acids joined through peptic bonds
- Secondary - structural configuration of amino acid residues are close neighbours
- Tertiary - folding, bending of polymer chains as well as hydrophobic and hydrophilic interactions
- Quaternary - proteins may consist of more than one polypeptide chains
Define cell metabolism
All chemical reaction processes that occur in the cell, cell constituents converted to different compounds
Define metabolic regulation
The role of enzymes:
- Enzymes are conjugated proteins which are biological catalysts
- Highly specific enzymes
Define central dogma and its 3 main processes.
· Central dogma - conversion of genetic code held within cell DNA into protein which controls process within the cell
- 3 main processes
=> replication - info stored in DNA replicated by forming identical molecule
=>transcription - info segments contained in DNA copied onto strands of RNA
=>translation - info used to make polypeptides/proteins with specific sequence by RNA sequence
Define anabolism
Anabolism - (or biosynthesis) - production of complex biological polymers and requires energy e.g. photosynthesis
Define catabolism
Catabolism - process that occurs within cell whereby larger complex compounds are broken down into smaller simpler products and releases energy for the cell
