Exam #2 (2 & 6) Flashcards
Element
A substance that consists of only one kind of atom and cannot be separated into simpler parts by chemical methods; 92 are naturally occuring;
4 Most Common Elements in Organisms
- Carbon
- Hydrogen
- Oxygen
- Nitrogen
Atoms
The basic units of all matter
Subatomic Particles Composing Atoms
- Neutrons: uncharged, found in the nucleus
- Protons: positively charged, found in the nucleus
- Electrons: negatively charged, form cloud around the nucleus
Atomic Number
The number of protons in the nucleus
Atomic Weight (Mass)
The sum of the number of protons and neutrons found in an atom
Isotope
Forms of the same chemical element that differ in their number of neutrons; useful tools in biological research
Molecule
Two or more atoms held together by chemical bonds
Chemical Bond
Form when atoms lose, gain, or share the electrons in their outer shell to achieve the most stable state
Ionic Bond
A strong chemical bond resulting from the attraction of positively and negatively charged ions; resulting product is called a salt
Covalent Bond
Strong chemical bond formed by the sharing of electrons between atoms; share pairs of valence electrons
Hydrogen Bond
Weak attraction between a positively charged hydrogen atom of one compound and a negatively charged atom of another compound; charges of the two atoms are due to polar covalent bonds
Ion
An atom that gains or loses an electron; becomes positively or negatively charged
Cation
Positively charged ion
Anion
Negatively charged ion
pH
Scale of 0 to 14 that expresses the acidity or alkalinity of a solution
Buffer
Substances in a solution that acts to prevent changes in pH
Macromolecules
Large molecules that contain 10s of atoms to billions of atoms; complex enough that life is usually necessary to make them
- organic: the molecules contain at least Carbon and Hydrogen
4 Types of Macromolecules
- Carbohydrates: sugars, starch, glycogen, chitin, celluose, peptidoglycan (most composed of ringed molecules)
- Lipids: triglycerides, phospholipids, steroids
- Proteins: building blocks, enzymes
- Nucleic Acids: DNA, RNA
Monosaccharides
Simple sugars; primary choice to make cellular energy (ATP)
Polysaccharides
Carbohydrates that cells make to store energy in the form of a carbohydrate; glycogen in animals, cellulose in plants; chitin, cellulose, and peptidoglycan are complex carbohydrate molecules that cells use as building blocks of cell walls
Triglycerides
Fat molecules that cells construct to store energy
Saturated Fat
Fatty acid that contains no double bonds
Unsaturated Fat
Fatty acid with one or more double bonds
Phospholipids
Fat molecules that cells construct as building blocks for cell membranes and other membrane-bound organelles
Steroids
Fat molecules that have four carbon rings connected to each other; cholesterol and some hormones
Proteins
Made up of smaller amino acid molecules (20 different types); most made up of about 200 adjacent amino acids; conduct most of the cellular work and are used as building blocks for cell walls, cell membranes, flagella, cilia, and organelles; also used as enzymes that allow cells to create chemical reactions
Nucleotides
Small molecules that make up nucleic acids
Enzymes
Proteins that function as biological catalysts, facilitating the conversion of a substrate into a product; work on only one type of substrate; end is -ase
Catalyst
Substance that speeds up the rate of a chemical reaction without being altered or depleted in the process
Active Site
Small crevices on enzymes that allow a substrate to precisely bind to it
Enzyme-Substrate Complex
The temporary binding of an enzyme and a substrate during which the activation energy is lowered for the reaction
Cofactors and Coenzymes
Inorganic (minerals) and organic (vitamins); loosely attach to enzymes and complete the active site; without them, enzymes cannot function correctly and normal metabolism is impaired
Environmental Factors That May Disrupt the Normal Shape and Function of Enzymes
- Temperature: speed up or slow down rate of reactions; denaturation at too high temps
- Salt Concentration: most operate best at low concentrations
- pH: best at values slightly above 7
Allosteric Regulation
The temporary binding of regulatory molecules to the allosteric site of an enzyme; can make enzymes more or less reactive (starting or stopping a chemical reaction)
Competitive Inhibition
An inhibitor molecule binds to the active site of an enzyme and prevents the true substrate from binding
Non-Competitive Inhibition
An inhibitor molecule binds to the allosteric site of an enzyme and permanently changes the shape of the enzyme
Metabolism
The sum of all chemical reactions that occur within a cell
Anabolic Chemical Reactions
Chemical reactions in which smaller molecules are joined together to build larger molecules; typically require an input of energy; dehydration synthesis
Catabolic Chemical Reactions
Chemical reactions in which larger molecules are broken apart into smaller ones; typically release energy; hydrolysis; release the energy stored within covalent bonds of macromolecules and produce ATP
ATP (Adenosine Triphosphate)
A modified RNA nucleotide with three phosphate groups; the covalent bond attaching the last phosphate group is considered a high energy bond that a cell uses for energy
REDOX (reduction-oxidation) Reactions
Transfer of electrons (and H+) from one molecule to another; one becomes reduced (gains) and one becomes oxidized (loses); always occur together
NAD+ and FAD+
Molecules that act as electron acceptors in catabolic chemical reactions; one is reduced to NADH, the other is reduced to FADH2
Glycolysis: Simplified Reaction
Glucose (6 carbons) + 2 ATP + 2 NAD+ + 10 enzyme mediated chemical reactions —-> 2 pyruvate (3 carbons) + 4 ATP + 2 NADH
Steps of Glycolysis
- First step in the degradation of sugars
- One glucose enters the pathway
- Two pyruvate are produced at the end of the 10 step process
- Four ATP are produced, two used to initiate reactions (2 ATP generated net)
- Two pairs of electrons passed to both NAD+, reducing both of them to NADH
- No free oxygen is consumed
Krebs Cycle: Simplified Reactioin
Pyruvate + 4 NAD+ + 1 FAD+ —-> 3 CO2 + 4 NADH + 1 FADH2 + 1 ATP
Summary of Krebs Cycle
- For each glucose molecule, 2 pyruvate enter the pathway
- The 3-carbon pyruvate molecule is broken down one carbon at a time over a series of 9 reactions, producing CO2 as a product
- Everything except the first step is cyclic: pyruvic acid + NAD+ —-> Acetyl CoA (2C) + CO2 + NADH
- Acetyl CoA will then combine with a 4-carbon oxaloacetic acid molecule forming a 6-carbon citric acid molecule; two additional carbons removed one at a time
- The energy released from the reactions are lost as heat and stored in the electron carriers using redox reactions
- Produces 1 ATP, 4 NADH, 1 FADH2
Electron Transport Chain
NADH and FADH2 are oxidized into NAD+ and FAD+; the electrons are transferred to a series of five to seven electron acceptors (proteins) found within a membrane; these electrons have energy that will construct ATP molecules for the cell
ATP Synthase
An enzyme used to make ATP; found in the cell membranes of prokaryotic organisms and in the inner mitochondrial membrane of eukaryotic organisms
Terminal Electron Acceptor (TEA)
The last molecule to accept the electrons found in the NADH and FADH2 molecules; oxygen in aerobic respiration and oxygen containing salts in anaerobic respiration
Aerobic Respiration
Krebs + ETC using oxygen; oxygen is reduced to water
Anaerobic Respiration
Krebs + ETC using inorganic molecules
Fermentation
Pyruvate is further oxidized without free oxygen; unless glycolysis is included in the calculations, these additional pathways do not produce usable energy (ATP); main purpose is to convert NADH into NAD+ to be used in glycolysis
Two Main Types of Fermentation
- Alcohol (yeast, some bacteria)
- Acidic (humans, some bacteria
Propionibacterium
Conduct acidic fermentation that gives Swiss cheese its characteristic flavor; the holes represent the CO2 escaping the cheese
Mixed Acid Fermentation
Type of Fermentation in which some bacteria produce a mixture of acetic, lactic, succinic, and formic acids (super fermenters: lower the pH of medium below 4.0)
Drawbacks to Fermentation
- Wastes large amounts of energy found in glucose; only net of 2 ATP produced from a single glucose molecule; chemical reactions are only 2% efficient
- The waste products produced can impede or stop cell function
Other Carbohydrates (besides glucose) Used to Produce ATP
- Other sugars (fructose, sucrose, lactose, etc.) will first meed to be converted into glucose and then proceed into glycolysis
- Polysaccharides are broken down into multiple glucose (1000+) and then each is placed into glycolysis
Triglycerides Used to Produce ATP
- Must first be broken down to its component molecules: 3 fatty acids and a glycerol molecule
- Fatty acids are converted into numerous Acetyl CoA by beta-oxidation
- Acetyl CoA are inserted into the Krebs Cycle, bypassing the transition step
- Glycerol is converted into pyruvate which is inserted into the Krebs cycle
- Approximately 458 ATP can be generated from a single one of these molecules
Proteins Used to Produce ATP
- Can be used if the cell does not have enough carbohydrates or triglycerides available to use as energy for ATP production
- First, broken down into individual amino acids
- NH2 must be removed from each amino acid (deamination) and converted to urea
- The remaining portions of the amino acids are converted into one of the substrates of the Krebs Cycle
- Each amino acid is reduced into NADH and FADH2 in the Krebs Cycle and used later to generate ATP in the ETC (12-16 ATP are generated per amino acid)
