Cell Biology. A few notes: Biological Molecules. Mono = one Monomer = one piece. Poly = many Polymer = many pieces

Transcription

1 Cell Biology Biological Molecules A few notes: Mono = one Monomer = one piece - a basic building block - able to bond into long chains Poly = many Polymer = many pieces - many molymers 1

2 Polymerization any process is which relatively small molecules (monomers) combine chemically to produce a very large chain-like network molecule called a polymer Condensation Synthesis Reaction Aka synthesis or condensation or dehydration synthesis Forms a polymer Is an ANABOLIC (building-up) reaction Water = by-product formed Monomers Water Polymer 2

3 Hydrolysis Reaction Literally means reaction with water A chemical process in which a molecule is cleaved into two parts by the addition of WATER Is a CATABOLIC (breaking down) reaction Water is needed Polymer Water Monomers 3

4 CARBOHYDRATES CARBOHYDRATES CHO sugars Primarily consist of C, H, O Approximate Ratio of 1:2:1 Empirical or simplest formula for a carbohydrate is CH 2 O Energy Source Suffix - ose GLUCOSE, FRUCTOSE 4

5 Monosaccharides Simple sugars that comprise ALL CHO s All have the same chemical formula (C 6 H 12 O 6 ) Therefore called ISOMERS ( equal parts ) Isomers - having the same chemical composition but with different structural arrangement Monosaccharides E.g. GLUCOSE (C 6 H 12 O 6 ) blood sugar A hexose sugar E.g. FRUCTOSE (C 6 H 12 O 6 ) Found in fruits, honey, some vegetables A hexose sugar Note: the molecular formula is the same but the shape of the ring and arrangement of the hydrogen and hydroxyl groups are different. 5

6 Disaccharides (di = two; saccharide = sugar) When 2 monosaccharides (monomers) combine chemically they form a disaccharide (dimer) 3 most common forms: 1. SUCROSE (table sugar) - glucose + fructose 2. MALTOSE (malt sugar; grain sugar) - glucose + glucose 3. LACTOSE (milk sugar) - glucose + galactose Like monosaccharides, they are soluble in water They cannot be stored in the body Glycosidic bond needs to be broken by hydrolysis to form simple sugars for energy release in cell respiration. 6

7 Polysaccharides (poly = many; saccharide = sugar) Long chains of many monosaccharides (monomers) joined together by glycosidic bonds to form a polysaccharide (polymer) 3 important polysaccharides (all are polymers of GLUCOSE) 1. STARCH - plant storage polysaccharide - a mixture of Amylose and Amylopectin 2. GLYCOGEN - animal storage polysaccharide - found in muscle and liver primarily - broken down very quickly to glucose for energy 3. CELLULOSE - in plants only - cannot be broken down by AMYLASE enzyme and thus cannot be digested in humans - Straight chain - Few side branches - Plant source - Unbranched - Plant source - Highly branched - Many side branches - Animal Source 7

8 Main Functions of Carbohydrates Provide a quick, short term ENERGY source for all living organisms Structural role in plants (Cell Wall contains cellulose) Cell-Cell recognition by CHO on surface of cell membrane Storage compounds (starch and glycogen) 8

9 Test your Knowledge 1. This molecule shown on the left is an example of: a) disaccharide b) starch c) monosaccharide d) polysaccharide 2. The elements C, H, O are generally found in what ratio? 3. What is the empirical or simplest formula of any carbohydrate? 4. What is the reaction in which the addition of water causes the subunits of a macromolecule to separate and degradation takes place? 5. Plants store glucose as whereas animals store glucose as. 6. The process of joins two monosaccharides to form A disaccharide. LIPIDS 9

10 LIPIDS Mixed group of HYDROPHOBIC compounds Insoluble in water Contains fats, oils, waxes, rubbers, sterols: Composed of C, H, and O (same as Carbs) Energy Storage (vs Carbs. - Energy Source ) C-H bond represents usuable energy Lipids have double the C-H bonds of a Carbohydrate 1. Triglycerides (FATS and OILS) Commonly called FATS and OILS FATS - Solids at room temperature OILS - Liquid at room temperature Made up of glycerol and fatty acids Ra, Rb, Rc represent groups of carbon and hydrogen atoms in which the carbon atoms are attached to each other in an un-branched chain. 10

11 Glycerol Central component in fats and oils A three-carbon alcohol Contains three - OH hydroxyl groups Soluble in water (hydrophilic) Fatty Acids A carboxylic acid Carboxyl group (COOH) plus a chain of atoms (mostly C and H) Water insoluble (hydrophobic) Contain an even number of C-atoms (4-36) Saturated Fatty Acids All bonds are single Number of atoms attached to each carbon is the maximum of 4 (thus is saturated ) Unsaturated Fatty Acids Some double bonds kinky chain 11

12 Fatty Acids Saturated Unsaturated energy More - b/c more C-H Less - b/c fewer C-H naming If it has 1 C=C Then monounsaturate If it has many C=C then polyunsaturate (omega 3&6 Essental FA s) 2. Phospholipids Major constituent of cell membranes ( lipid bilayer ) Precursor of prostaglandins Short-lived hormones that operate close to home ie. Uterine smooth muscle contraction associated with birthing ie. Found in seminal fluid; decreases female immune response to sperm 12

13 Structure Similar to triglycerides HOWEVER one of the three fatty acid is replaced by a phosphate functional group Hydrophobic Tails Hydrophillic Head Phosphate Group - ORANGE Fatty Acid Groups - BLUE Glycerol - RED 13

14 3. Steroids Cholesterol component on cell membranes in animals and functions to moderate membrane fluidity Bile Salts Help to emulsify dietary fats Hormones (estrogen and testosterone) Vitamine D Aids in calcium uptake by bones Structure Based on a molecules with four fused carbon rings Each steroid differs by arrangements in the rings and by functional group attached to it 14

15 Low Density Lipoproteins (LDL) bad cholesterols LDL carries cholesterol from liver to cells Used as a structural component of cell membranes or converted to steroid hormones Too much LDL is associated with artiosclerosis High Density Lipoproteins (HDL) good cholesterols Acts like a cholesterol scavenger so excess cholesterol can be removed and converted to bile acids and excreted through digestive tract Function of Cholesterol Structural component of cell membranes Essential component of myelin sheath that insulates neurons Precursor for lipid soluble vitamins (ADEK) Precursor for steroid hormones 15

16 Test your Knowledge 1. is the precursor of : a) testosterone, cholesterol b) cholesterol, lipids c) cholesterol, testosterone and estrogen d) testosterone and estrogen, cholesterol 2. are made of one glycerol and three fatty acid molecules that can be recognized by their -COOH ending a) steroids b) phospholipids c) triglycerides d) all of the above 3. are liquid at room temperature and have between any two carbon atoms. 4. Name two different types of steroids. 5. Why are fats referred to as TRIGLYCERIDES? PROTEINS 16

17 PROTEINS Polymers of AMINO ACID monomers e.g. antibodies, enzymes, most hormones, hemoglobin. structural support in much of our tissues Composed of C, H, O, N (sometimes Sulfur) Tend to be BIG compounds Amino Acid (monomer) R- Group (Radical Group) - chain of atoms Rest of Polypeptide (Polymer) Two or more amino acids bonded by a covalent (peptide) bond Formed by dehydration synthesis Synthesis of a Dipeptide 17

18 Protein Structure: The shape of a protein is critical to its function Protein Structure can be described in four levels: Primary Secondary Tertiary Quaternary Primary Structure Shape: linear sequence of amino acids Like strings of pearls Linked by peptide bonds (C-N) 18

19 Secondary Structure Shape: helical or pleated sheet Looks like primary proteins coiled into a slinky Held in place by hydrogen bonds Secondary Structure Pleated Sheet 19

20 Tertiary Structure Shape: globular Secondary protein folded back upon itself and creating a 3-D structure Globular shape determines its function Folding caused by covalent bonding between R-groups in structure Part of this protein is hydrophilic Twists and turns to maximize surface area in contact with water Part of this protein is hydrophobic Twists and turns to minimize surface area in contact with water Quaternary Structure Shape: Multimeric Composed of two or more polymers joined together e.g Hemoglobin (made of two alpha and two beta chains) 20

21 Protein Denaturation: Recall: A protein s shape is critical to function A small change is structure can reduce or destroy function Occurs when proteins are exposed to: Extremes of temperatures (e.g heat breaks H-bond) Extremes of ph (distrupts H-bond) May unfold or DENATURE proteins = loss of shape Function of Proteins: 1. Enzymes Catalysts that speed up chemical reactions Function determined by teritary structure End in -ase (e.g. amylase, lipase) 2. Structural Proteins Keratin - builds hair and nails Collagen - give strength to skin, cartilage, tendons, ligaments Actin and Myosin - bone and muscle fibres 3. Membrane Proteins Proteins that act as channels or pores, carriers, and pumps 21

22 Function of Proteins: 4. Hormones Chemical messengers that influence cellular functions (metabolism, growth, development and homeostasis) 5. Plasma Proteins Plasma = liquid portion of blood consists of 7-8% protein Contribute to blood osmotic pressure by pulling water from tissues E.g. Albumin, globulins, fibrinogen Test your Knowledge 1. What is the basic unit of protein? 2. How many different types of amino acids are there? 3. Name three different types/levels of protein structure and describe the bonding associated with each. 4. What are three major functions of proteins and briefly describe each. 5. Draw a structural diagram to represent a typical amino acid. 22

23 NUCLEIC ACIDS NUCLEIC ACIDS Two Types: DNA - Deoxyribonucleic Acid RNA - Ribonucleic Acid C, O, H, N, P Function Sugar (pentose) DNA Genetic information DNA synthesis Deoxyribose sugar RNA Protein synthesis Ribose sugar Shape Double Helix Single Strand 23

24 Structure of DNA Decribed by Watson and Crick (1950 s) as a double helix Composed of many NUCLEOTIDES (monomers) Nucleotides have three main parts: 1. A phosphate group 2. A pentose (5-C) sugar (see previous chart) 3. A nitrogen containing base DNA is a polymer of nucleotides: Sugars and phosphates form a linear sugar backbone Bases project from the sides of the backbone DNA has 4 different bases: 1. Adenine (A) 2. Thymine (T) *replaced with uracil in RNA* 3. Guanine (G) 4. Cytosine (C) 24

25 DNA Purine Pyrimidine Adenine Thymine A T Complementary pairs Guanine Cytosine G C RNA Purine Pyrimidine Adenine * Uracil * A U Complementary pairs Guanine Cytosine G C 25

26 Complementary Base Pairing Types of RNA (a brief intro ) mrna (messenger RNA) trna (transfer RNA) rrna (ribosomal RNA) 26

27 mrna Single stranded Transcribed from DNA template mrna carries the a.a. sequence ( blueprint ) from the nucleus to the site of protein synthesis (ribsomes) trna Single stranded; cloverleaf tertiary structure Transports a specific a.a. to the ribosome for assembly into an elongating polypeptide (translation) 27

28 rrna Central component of ribosomes where proteins are manufactured Catalyzes the assembly of amino acids into a polypeptide chain Single stranded ATP - Adenosine Triphosphate High ENERGY molecule ( Energy Currency ) Releases energy for all metabolic work in the cell Structure: 1. Adenine 2. Ribose sugar (5-C Sugar) 3. Three (3) phosphate groups 28

29 Last two phosphate bonds can be easily broken and will releas energy : Test your Knowledge 1. What do the letters DNA and RNA stand for? 2. DNA has four different types of bases. What are they called? 3. Nucleic Acids are composed of many nucleotides. They are composed of three main parts. Name these parts. 4. T/F: DNA has a sugar-nitrogen backbone. 5. T/F: The base Guanine will always bond with Cytosine. 6. Who were the first scientists to describe DNA as a double helix structure? 7. What do the letters ATP stand for? 8. Describe the three subunits that make up an ATP molecule. 29