Exam #2 (2 & 6) Flashcards Preview

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Flashcards in Exam #2 (2 & 6) Deck (60):
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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;

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4 Most Common Elements in Organisms

- Carbon
- Hydrogen
- Oxygen
- Nitrogen

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Atoms

The basic units of all matter

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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

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Atomic Number

The number of protons in the nucleus

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Atomic Weight (Mass)

The sum of the number of protons and neutrons found in an atom

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Isotope

Forms of the same chemical element that differ in their number of neutrons; useful tools in biological research

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Molecule

Two or more atoms held together by chemical bonds

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Chemical Bond

Form when atoms lose, gain, or share the electrons in their outer shell to achieve the most stable state

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Ionic Bond

A strong chemical bond resulting from the attraction of positively and negatively charged ions; resulting product is called a salt

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Covalent Bond

Strong chemical bond formed by the sharing of electrons between atoms; share pairs of valence electrons

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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

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Ion

An atom that gains or loses an electron; becomes positively or negatively charged

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Cation

Positively charged ion

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Anion

Negatively charged ion

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pH

Scale of 0 to 14 that expresses the acidity or alkalinity of a solution

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Buffer

Substances in a solution that acts to prevent changes in pH

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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

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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

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Monosaccharides

Simple sugars; primary choice to make cellular energy (ATP)

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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

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Triglycerides

Fat molecules that cells construct to store energy

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Saturated Fat

Fatty acid that contains no double bonds

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Unsaturated Fat

Fatty acid with one or more double bonds

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Phospholipids

Fat molecules that cells construct as building blocks for cell membranes and other membrane-bound organelles

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Steroids

Fat molecules that have four carbon rings connected to each other; cholesterol and some hormones

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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

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Nucleotides

Small molecules that make up nucleic acids

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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

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Catalyst

Substance that speeds up the rate of a chemical reaction without being altered or depleted in the process

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Active Site

Small crevices on enzymes that allow a substrate to precisely bind to it

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Enzyme-Substrate Complex

The temporary binding of an enzyme and a substrate during which the activation energy is lowered for the reaction

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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

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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

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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)

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Competitive Inhibition

An inhibitor molecule binds to the active site of an enzyme and prevents the true substrate from binding

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Non-Competitive Inhibition

An inhibitor molecule binds to the allosteric site of an enzyme and permanently changes the shape of the enzyme

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Metabolism

The sum of all chemical reactions that occur within a cell

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Anabolic Chemical Reactions

Chemical reactions in which smaller molecules are joined together to build larger molecules; typically require an input of energy; dehydration synthesis

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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

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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

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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

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NAD+ and FAD+

Molecules that act as electron acceptors in catabolic chemical reactions; one is reduced to NADH, the other is reduced to FADH2

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Glycolysis: Simplified Reaction

Glucose (6 carbons) + 2 ATP + 2 NAD+ + 10 enzyme mediated chemical reactions ----> 2 pyruvate (3 carbons) + 4 ATP + 2 NADH

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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

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Krebs Cycle: Simplified Reactioin

Pyruvate + 4 NAD+ + 1 FAD+ ----> 3 CO2 + 4 NADH + 1 FADH2 + 1 ATP

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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

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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

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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

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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

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Aerobic Respiration

Krebs + ETC using oxygen; oxygen is reduced to water

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Anaerobic Respiration

Krebs + ETC using inorganic molecules

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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

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Two Main Types of Fermentation

- Alcohol (yeast, some bacteria)
- Acidic (humans, some bacteria

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Propionibacterium

Conduct acidic fermentation that gives Swiss cheese its characteristic flavor; the holes represent the CO2 escaping the cheese

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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)

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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

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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

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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

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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)