The topic: Molecular and Cellular Basis for Life

Transcription

1 What is expected of you? MOLECULAR AND CELLULAR BASIS OF LIFE Professor Luke O Neill School of Biochemistry and Immunology laoneill@tcd.ie Dr Suzanne Cloonan School of Biochemistry and Immunology 1. Make the most of being here 2. Engage with the subject: Attend the lectures and practicals Read (Campbell.plus whatever you like the relevant chapters in Campbell (7 th Edition): Chapter 1: p2-p12 Chapter 2: p32-p33, Chapter 4: p58-p66 Chapter 5:p68-p78, p86-p89 Chapter 6 and 9: miscellaneous parts of these chapters (use lecture notes as ke 3. Pass the exams in May How? - Make sure you have a good set of lecture notes and that you understand them (ask questions ) - Get past exam papers Life can be viewed at many different levels: ORGANISM LEVEL (consisting of many organ systems) HIGHER LEVELS (populations, communities and ecosystems) ORGAN SYSTEM LEVEL (digestive system) The topic: Molecular and Cellular Basis for Life ORGAN LEVEL (stomach) ORGANELLE LEVEL (cell nucleus) MOLECULAR LEVEL (DNA) TISSUE LEVEL (smooth muscle tissue) CELLULAR LEVEL (smooth muscle cell) ATOMIC LEVEL (oxygen) 1

2 4 main classes of large biological molecules 1. Carbohydrates sugar polymer (polysaccharides) serve as fuel. 2. Lipids triacylglycerides, fatty acids, steroids and phospholipids, serve as energy stores and provide insulation, form cell membranes. 3. Nucleic acids DNA and RNA, enable living organisms to reproduce. 4. Proteins amino acid polymers, the molecular tools of the cell 50% of dry mass of cells encoded for by our genes Proteins Dr. Suzanne Cloonan Proteins from genotype to phenotype Types of protein - Proteins are the key functional molecules in life - Proteins have many structures, resulting in a wide range of functions Gene/c informa/on genotype Messenger RNA (mrna) Physical trait phenotype 2

3 1. Enzymatic proteins Function is to accelerate chemical reactions Act as catalysts- reagents that selectively speed up chemical reactions without being consumed by the reaction Eg. Digestive enzymes catalyse the hydrolysis of the polymers in food : eg.s lipase, lactase... Fat globule LIPASE Free faay acids and glycerol Lumen of small intes/ne 1. Enzymatic proteins Eg. 2 RNA polymerase Binds DNA and pulls the double strand apart Allows for generation of mrna Ultimately allowing for the generation of protein Bile salts Epithelial Cell layer The phenotype of a biological system is entirely dependent on this enzyme 2. Structural proteins Function is support Long chained molecules Eg. 1. silk fibroin silk fibres used by insects and spiders. These are both strong and flexible 2.Structural proteins Eg 2. Keratin, is the protein of hair, horns, feathers and other skin appendages Rigid and strong 3

4 2.Structural proteins Crosslinking and intertwining allows for many properties- Can be flexible and elastic eg. Wool fibres Can be strong and rigid eg. Collagen fibres Collagen and elastin provide a fibrous framework in animal connective tissue 3. Storage proteins Function of these is the storage of amino acids Metabolism of these proteins provides building blocks to make new proteins Eg. Ovalbumin, in the developing embryo Eg. Casein, in milk for baby mammals 4. Transport Proteins Function is the transport of other substances Eg 1. Hemoglobin, a protein of vertebrate blood, contains iron and transports oxygen from the lungs around to other parts of the body 4. Transport Proteins Transport proteins can also transport molecules across cell membranes transmembrane proteins Eg. Aquaporins- transport water across membranes Eg. Glucose transporter- shuttles glucose into cells where it is needed rapidly for cellular energy Cystic fibrosis=no functioning Chloride channels build up of mucus in the lungs 4

5 5. Hormonal Proteins 5. Hormonal Proteins Function is the coordination of an organism s activities Eg.s Insulin and Glucagon- regulate the concentration of blood sugar levels Glucose levels need to be kept at a constant concentration in the blood -- fuel for energy -- carbon skeleton 5. Hormonal Proteins 6. Receptor Proteins Type 1 diabetes can result in hyperglycaemia Function is to allow cells to respond to chemical stimuli The stimuli Receptor proteins detect are called ligands (eg. hormone proteins) When a receptor binds its ligand it usually changes the shape of the receptor (usually transmembrane) Signal transduction- the result of receptor binding its ligand 5

6 6.Receptor Proteins Allows for a response to the external environment Eg. Insulin Receptor Extracellular domain 6.Receptor proteins Eg. Receptors at nerve endings Detect neurotransmitters such as Serotonin, dopamine Plasma membrane Intracellular domain Dopamine- motor ac/vity behaviour mo/va/on/reward L- Dopa used in Parkinson s Disease Signal transduc/on: Cell knows to take in glucose `Conformational change induced by insulin binding Serotonin- mood sleep aaen/on/learning Prozac used against depression 7. Contractile and Motor Proteins Function is movement Eg. Actin and Myosin are responsible for -the movement of muscle fibres -altering the shape of cells 7.Contractile and Motor proteins Eg. Flagellin and others are responsible for the movement of organelles Flagellin is the main constituent of a bacterial flagellum 6

7 8.Defensive Proteins Function is to protect against disease Eg. Antibodies that help combat bacteria and virus Antibodies recognise antigens through their shape Highly variable Disease XLA-no circulating Abs- susceptible to infection Summary of 8 types of protein 1. Enzymatic 2. Structural 3. Storage 4. Transport 5. Hormonal 6. Receptor 7. Contractile and Motor 8. Defensive Proteins What is the structure of a protein? Protein shape is very important to its function proteins interact with other proteins Eg. antibody Each of the ~25,000 human proteins have specific structure and function Diverse functions - diverse structures Unique function = unique 3D shape Protein Shape=Conformation 7

8 Polypeptides Proteins Are polymers of amino acids (aa) aa-aa-aa-aa-aa-aa-aa-aa-aa-aa-aa-aa-aa-aa polymer of aa = polypeptide A protein Consists of one or more polypeptides polypeptide(s) = protein Amino Acid Monomers Amino acids Are organic molecules possessing both carboxyl and amino groups Differ in their properties due to differing side chains, called R groups Backbone of each aa 20 different R groups = 20 different amino acids Amino Acid Monomers Amino acids Are organic molecules possessing both carboxyl and amino groups Differ in their properties due to differing side chains, called R groups 4 subgroups of Amino acid - There are 20 naturally- occurring amino acids - Grouped into 4 subgroups: - Non-polar: hydrophobic -Polar: hydrophilic - Acidic: hydrophilic - charge Backbone of each aa - Basic: hydrophilic + charge 20 different R groups = 20 different amino acids 8

9 1. Non-polar amino acids hydrophobic / water insoluble 2. Polar amino acids hydrophilic / water soluble Electrically charged amino acids water soluble 3. Acidic 4.Basic The topic: Molecular and Cellular Basis for Life 9

10 Campbell (7 th Edition): Chapter 1: p2-p12 Chapter 2: p32-p33, Chapter 4: p58-p66 Chapter 5:p68-p78, p86-p89 Chapter 6 and 9: miscellaneous parts of these chapters (use lecture notes as key) JM Berg, JL Tymoczko and L Stryer, Biochemistry, 6th ed, WH Freeman, New York, (Chapters 1and 2) Other good Biochemistry textbooks Molecular Cell Biology Books 10