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Chapter 6 continued Lipids, Proteins, and Nucleic Acids Lipids Lipids • Nonpolar molecules HH H HH HH H HH – Long chains of –C-C-C-C-C-C-C-C-C-C H H HH H HH HH H H – Contain large amounts of H – Store large amount of energy -9.0 Calories/gram – Oils (if liquid at room temp.) – Fats (if solid at room temp.) – Waxes – Steroids To assemble a triglyceride . . . H H H H H H H H H H C C C C C C C C C C HO H H H H H H H H H H O H H H H H H H H H C C C C C C C C C C H H H H H H H H H O C 1 OH C 2 OH C 3 OH Glycerol C C HO 3 Fatty Acids Typical Triglyceride 3 fatty acids Glycerol Phospholipid: variation of a triglyceride • found in all cell membranes and membranes of organelles Some lipids have an unusual shape Cholesterol is in cell membranes Proteins • Provide the basic building blocks for all tissues in organisms • Contain 4.4 Calories of energy/gram • Basic building block is the amino acid -- 20 different kinds ? Central carbon O ? R = variable group (20 kinds of R) R group examples To join 2 amino acids . . . H N H H2O Condensation _____?_____ A dipeptide Basic polypeptide Types of foldings and spiraling to give the final shape to the protein Not a protein until polypeptide finishes folding Enzymes . . . • Are made of globular proteins: have a definite 3-D shape • Speed up reactions so they can occur at body temperature; enzymes are catalysts • Can be used repeatedly to do the same reaction – Eventually they “wear out” and are replaced • Have a groove or indentation in the surface called the active site – The molecules involved in the reaction fit into the groove and are called the substrate molecules How sucrase “digests” sucrose Hydrolysis Sucrase What’s the difference in the active site before and after accepting the sugar molecule? Before After Induced fit: an adjustment by the enzyme to fully fit to the substrate • Enzymes regulate nearly all metabolic processes: The sequence below is called a metabolic pathway Enzyme 1 Enzyme 2 Enzyme 3 Enzyme 4 A B C D E Initial Final molecule product Intermediate molecule molecules • Environmental conditions affect an enzyme’s shape -denaturation happens to the enzyme outside optimum ranges and the enzyme cannot fit to a substrate, therefore it becomes inactive Nucleic Acids • DNA, 3 kinds of RNA – monomer is called a nucleotide Kinds of nitrogen bases Bases linked together to form 1/2 DNA Complete DNA molecule DNA in double helix form Dog offered for free; owner can’t stand the way it stares. (Internet humor) End It’s time for TEST Review Easy Questions Question 1 The movement of particles from an area of higher concentration to an area of lower concentration is A. homeostasis B. diffusion C. dynamic equilibrium D. Brownian movement Question 2 Which of the following best describes a covalent bond? A. Protons are gained or lost. B. Electrons are gained or lost. C. Electrons are shared. D. Protons are shared. Question 3 What causes water to creep up thin tubes? A. Water has a high surface tension. B. Water has a high heat of vaporization. C. Water expands when it freezes. D. Water has an attraction for itself and for other molecules. Question 4 The compound HCl gives off hydrogen ions in water. What type of compound is HCl? A. an acid B. a base C. a buffer D. a salt Question 5 Which of the following is NOT associated with lipids? A. glycerol B. saturated fatty acids C. unsaturated fatty acids D. nucleic acids Medium Difficult Questions Question 1 A calcium atom has 20 electrons. When it reacts, it loses two electrons. How does this make calcium more stable? A. It will then have equal numbers of electrons and protons. B. Its outer shelf is now empty and the next lower level is full. C. Losing two electrons will make calcium neutral. D. It becomes a different isotope. Question At which enzyme concentration does all of the available substrate react with the enzyme? a. b. c. d. 0.3 mg/ml 0.15 mg/ml 0.22 mg/ml 0.05 mg/ml 4 3 2 1 0 0.1 0.2 0.3 0.4 0.5 Enzyme concentration (mg/ml) Question 2 Which of the following occurs when a solute reaches dynamic equilibrium in a solvent? A. The solute stops moving. B. The solute disappears. C. The solution is static. D. The particles keep moving. Question 3 What is the purpose of glycogen in muscle cells? A. Muscle cells use glycogen to make actin and myosin proteins. B. Muscle cells use glycogen to stimulate contraction. C. Muscle cells need glycogen to secrete hormones. D. Muscle cells break down glycogen to provide energy for contraction. Question Under which conditions is enzyme A most effective? a. 35˚C and pH 2.8 b. 40˚C and pH 3 c. 40˚F and pH 7 d. 40˚C and pH 6.8 Enzyme A Enzyme B Enzyme A Question The optimum environment for enzyme B is? a. b. c. d. a basic medium an acidic medium a neutral medium either acidic or basic Enzyme A Enzyme B Enzyme A Question 4 During the winter, ice floats on lakes. How can a solid float on a liquid? A. As ice forms, the molecules expand, making the ice less dense than cold liquid water. B. Ice has large air pockets, so it will always float on water. C. All molecules that form crystalline structures are less dense than liquids. D. Water molecules take up less surface area as they freeze. Question 5 How many total atoms are involved in the following equation? C02 + H20 ---> H2CO3 A. 4 B. 6 C. 7 D. 12 Difficult Questions Question 1 Whirligig beetles are small insects that are able to walk on the surface of water. What factor allows them to do this? A. Water is repelled from a whirligig beetle's body, so the beetle does not sink. B. Whirligig beetles have air pockets on their feet. C. Water attracts to itself, forming a surface tension "film" on top of the water. D. Whirligig beetles 'are less dense than water. Question 2 What is the function of stored starch in potatoes? A. It provides food for animals. B. It stores the food for seed production. C. It stores the energy captured during photosynthesis. D. It provides food for photosynthesis. Question 3 A cellulose molecule consists of 100 monosaccharides. How many water molecules would it take to completely hydrolyze the cellulose into the 100 monosaccharides? A. None, cellulose cannot be hydrolyzed. B. 50 water molecules C. 99 water molecules D. 100 water molecules Question 4 • Temperature, ionic conditions and the pH of surroundings all affect the rate at which these proteins catalyze chemical reactions. A. Surface protiens B. Enzymes C. DNA D. cyclo-pentane ring Question • What are the basic building blocks of proteins? a. b. c. d. Nucleic acids Peptide bonds Amino acids Glycerol and fatty acids Question • Glucose and fructose, with the formula C6H12O6, differ in _______. a. b. c. d. Number of atoms Arrangement of atoms Kinds of atoms Arrangement of electrons Question • Which of the following would yield the most energy per gram when oxidized? a. b. c. d. Starch Glycogen Proteins Fats Question • Most _____ (i.e. polysaccharides, nucleic acids, proteins, lipids) in cells and organisms are synthesized from a collection of simple precursors. a. b. c. d. Macromolecules Monomers Microscopy Mutations That’s all . . . Do well on your test :)