This image shows the primary structure of glycophorin A , a glycoprotein that spans the plasma membrane ("Lipid bilayer") of human red blood cells. Each RBC has some 500,000 copies of the molecule embedded in its plasma membrane. Fifteen carbohydrate chains are "O-linked" to serine (Ser) and threonine (Thr) residues. One carbohydrate chain is "N-linked" to the asparagine (Asn) at position 26. Two polymorphic versions of glycophorin A, which differ only at residues 1 and 5, occur in humans. These give rise to the MN blood groups The M allele encodes Ser at position 1 (Ser-1) and Gly at position 5 (Gly-5) The N allele encodes Leu-1 and Glu-5 Genotype to Phenotype Individuals who inherit two N alleles have blood group N. Individuals who are homozygous for the M allele have blood group M. Heterozygous individuals produce both proteins and have blood group MN . Glycophorin A is the most important attachment site by which the parasite Plasmodium falciparum invades human red blood cells.
Macromolecules in cells
Structure and Function ofCarbohydrates, Nucleic Acids, Proteins, Lipids
Organic compounds – chemicals synthesised by living things. Contain carbon. The basis of cells ◦ The big 4: Carbohydrates Lipids Protein Nucleic acid & vitamins Inorganic compounds (ie nutrients)mineral salts, water, gases
All cells use nucleic acids (DNA) to store information All cells use proteins as catalysts (enzymes) for chemical reactions All cells use lipids for membrane components All cells use carbohydrates for cell walls (if present), recognition, and energy generation All cells use nucleic acids (RNA) to access stored information
WATER: 90% of the chemical reactions, solvent,protoplasm regulate temperature Medium for transportMineral salts: dissolved in cytoplasm and Synethsis of macromolecues andand vacuoles in plant cells body tissues Assist Enzyme function (co- enzymes) Na+ and Cl- assist in water balance n cells and the function of nerve and muscle cellsGases (CO2 H20) dissolved in CO2: Photosynthesisprotoplasm or produced Respiration produc Regulates pH O2: releases energy during respiration Product of photosynthesis
◦ Monomers joined together◦ Macro = BIG◦ DNA◦ Proteins◦ Lipids & Carbohydrates (indirectly)◦ See table 2.2
Monosacharides can be joined to one another to form disaccharides, trisaccharides, ……..polysaccharides ◦ Saccharide is a term derived from the Latin for sugar (origin = "sweet sand") Carbohydrates classified according to the number of saccharide units they contain. ◦ A monosaccharide contains a single carbohydrate, over 200 different monosaccharides are known. ◦ A disaccharide - two carbohydrate units A polysaccharide - many carbohydrates on hydrolysis, examples are starch and cellulose.
All have general formula CnH2nOn (hydrates (H2O) of carbon) Simple sugars (glucose) are a source of quick energy in cells to produce ATP in the mitochondria Glucose + oxygen ATP Stored as polysaccharides, in some plant cells maybe dissolved in vacuoles
◦ Cell structure: Cellulose, LPS, chitin Chitin in exoskeletonCellulose in plant cell walls Lipopolysaccharides (LPS) in bacterial cell wall
Monosaccharides may also form part ofother biologically important molecules
Don’t dissolve in water – too big Cellulose Most abundant carbohydrate on the planet! ◦ Structural component of plant cell walls ◦ Indigestible by animals Starch ◦ Energy storage molecule in plants ◦ Can be digested by animals Glycogen ◦ Animal energy reserve ◦ Found primarily in liver and muscle
Cellulose is a linear polysaccharide in which some 1500 glucose rings link together. It is the chief constituent of cell walls in plants. Human digestion cannot break down cellulose for use as a food, animals such as cattle and termites rely on the energy content of cellulose. They have protozoa and bacteria with the necessary enzymes in their digestive systems. Only animals capable of breaking down cellulose are tunicates.
Starches are carbohydrates in which 300 to 1000 glucose units join together. It is a polysaccharide used to store energy for later use. Starch forms in grains with an insoluble outer layer which remain in the cell where it is formed until the energy is needed. Then it can be broken down into soluble glucose units. Starches are smaller than cellulose units, and can be more readily used for energy. In animals, the equivalent of starch is glycogen, which can be stored in the muscles or in the liver for later use.
Lipids ◦ Fatty acids (Polymers of CH2 units), few oxygen atoms ◦ Insoluble in water, greasy, oily ◦ Animals = fats, plants = oils ◦ Triglyceride = I glycerol molecule & 3 fatty acids
Function ◦ Energy Storage, stored in cytoplasm. Carbohydrates can be converted to fats in times of food abundance ◦ Structural function: Cell membranes and cell compartments ◦ Bi-layer structure Outer or plasma membrane Nuclear membrane Internal structures Er, Golgi, Vesicles, etc. Structural parts of hormones
Proteins serve many essential roles in the cell ◦ Are made up of polymers of amino acids, one chain is called a poly peptide ◦ Peptide bond holds amino acids together ◦ One or more polypeptides can be twisted together forming a protein ◦ The sequence and arrangement of amino acids determines the type of protein – just like the alphabet ◦ 20 naturally occurring amino acids The large number of amino acids allows huge diversity in amino acid sequence Cannot be stored, excreted as nitrogenous waste
Structure- form structural components of the cell including: ◦ Cytoskeleton / cell membranes Enzymes - control reactions Movement - Coordinate internal and external movement of cells, organells, tissues, and molecules. ◦ Muscle contraction, chromosome separation, flagella……… Transport-regulate transport of molecules into and out of the cell / nucleus / organelles. Communication-serve as communication molecules between different organelles, cells, tissues, organs, organisms. ◦ Hormones
Chemical properties of the amino acids yield properties of the protein!
The 3-D shape and properties of the protein determine its function. Shape and properties of protein determined by interactions between individual amino acid components. Four “levels” of protein structure ◦ Primary (Io), secondary (IIo), tertiary (IIIo), and quaternary (IVo) (sometimes).
All nucleic acids are made up of nucleotides (monomers) Made up of: a simple sugar, a base, a phosphate It is the sequence of bases which differs, providing the genetic code DNA –deoxyribonucleic acid RNA –ribonucleic acid So what’s the difference? ◦ RNA is one strand, DNA is 2
DNA RNAControls cells Messanger RNA – passes on information stored in DNA, transports a transcribed copy from the nucleus to the cytoplasm.Transmits inherited Assist the message to beinformation translated into proteinsMain component of chromatin
Information for all proteins stored in DNAin the form of chromosomes or plasmids.Chromosomes consist of two strands of DNA wrappedtogether in a left handed helix.The strands of the helix are held togetherby hydrogen bonds between the individualbases. The “outside” of the helix consists ofsugar and phosphate groups, giving the DNAmolecule a negative charge.
Chromosomes are composed of DNA and proteins. ◦ Proteins serve a structural role to compact the chromosome. ◦ Chromosomes can be circular, or linear. Both types contain an antiparallel double helix! ◦ Genes are regions within a chromosome. Like words within a sentence. For an animation of the organization of a human chromosome see: http://www.dnalc.org/ddnalc/resources/chr11a.html