AN INTRODUCTION TO BIOLOGY Nicky Mulder Acknowledgements: Anna Kramvis

Biology is the scientific study of living organisms and their interaction with the nonliving world Academic Press Dictionary of Science and Technology 2Copyright-Anna Kramvis

Is the ability to reproduce itself Is interrelatedness of components Requires energy for: Growing Protection Repairing damage Competing with others Producing offspring 3Copyright-Anna Kramvis Life….

Understanding life through Bioinformatics Isolate organism and sequence genes Predict what the protein looks like and what it does in the cell Send to lab to do experiments

Different levels of components Basic building blocks of life: chemicals, molecules, macromolecules

Basic building blocks in humans

Carbons form basis of many molecules

Macromolecules Many macromolecules consist of polymers A polymer is a large molecule built up from smaller building block molecules Monomers (a.k.a., subunits) are the building block molecules

Monomers and polymers MonomerPolymerBiomolecules monosaccharidespolysaccharidecarbohydrates amino acidspolypeptidesproteins nucleotidespolynucleic acidsRNA & DNA

Carbohydrates Also known as saccharides Consist of carbon, hydrogen and oxygen Basic formula Cm(H2O)n Four groups:  monosaccharides and disaccharides (sugars)  oligosaccharides –e.g. in cell membrane  polysaccharide –long chain, e.g. starch, glycogen, cellulose

Proteins Major constituent of cells (>50% dry weight) Highly sophisticated molecules/multi-molecular complexes Extremely large number of unique proteins exist They are polymers folded into specific conformations Conformation and functional-group chemistry controls function Made up of 20 different types of amino-acids Proteins define what an organism is, how it behaves, etc. (phenotype)

Lipids Many C-H bonds Lots of stored energy Hydrophobic Examples: fatty acid, hormones, cholesterol, phospholipid, etc.

Molecules and macromolecules make up cells

14Copyright-Anna Kramvis Cells differ among organisms

Cell sizes differ

Kingdoms of life Copyright-Anna Kramvis16 Viruses

Can only replicate in host Virions:  Genetic material  Protein coat  Lipid envelope

Viral infection Rambaut et al. Nature 2004

Prokaryotes Simple unicellular Cell membrane Cell wall Cytoplasm Genetic material

Two types of bacteria Determined by Gram stain Gram positive:  Blue stain  Peptidoglycan layer Gram negative  Red stain (counterstain)  Cell wall (cytoplasmic membrane, peptidoglycan layer, outer membrane)

Gram positives

Gram negatives

Membranes Copyright-Anna Kramvis23 commons.wikimedia.org

Cell Wall Copyright-Anna Kramvis24 faculty.ircc.edu

Archaebacteria Unicellular No nucleus or organelles Diverse habitats, some extreme Some similarities to prokaryotes (size) and eukaryotes (transcription)

Eukaryotes Uni- or multicellular Cell membrane Cytoplasm Organelles Nucleus Chromosomes

Variety of eukaryotes Mammals Fish Birds Insects, worms

Copyright-Anna Kramvis28 Eukaryotic organelles

Nucleus Organelle enclosed by membrane Holds genetic material DNA + histones -> chromosomes Controls replication and expression Envelope is triple membrane Nuclear pores allow movement in and out Nucleolus for assembling ribosomes

Microtubules Part of cytoskeleton Maintain cell structure Made up of polymers of tubulin Also involved in movement Centrosome is microtubule organizing centre, involved in cell cycle

Protein production Endoplasmic reticulum:  Rough –synthesizes proteins  Smooth –synthesizes lipids, etc Golgi apparatus:  Processes and packages proteins  NB for secreted proteins

Mitochondrion Number in cells varies Enclosed by membranes (outer and inner) Generate energy –ATP Also involved in signalling, cell cycle, death Implicated in diseases Has its own genome

Advantage of compartmentalizing Keeping “dangerous” proteins aside Enabling process of molecules, e.g. in nucleus Specialised environment for certain proteins

Summary Building blocks of life: chemicals -> molecules -> macromolecules -> organelles -> cells Different kingdoms of life each with different levels of complexity and cell types: virus -> bacteria -> archae -> unicellular eukaryotes -> multicellular eukaryotes