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Energy

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Ability to do work

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Potential energy

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Stored energy available to do work; Example: Chemical energy stored in bonds; A bicyclist at the top of a hill; Unburned gasoline

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Kinetic energy

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Energy in action; Energy used to do work. Examples: Light, sound, movement of molecules, muscle contraction

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Calories

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Units of measurement for energy; the amount of energy required to raise the temperature of 1 gram of water from 14.5°C to 15.5°C (1°C)

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Kilocalorie

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The most common unit for measuring the energy content of food; I kcal = 1,000 calories

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First law of thermodynamics

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Energy cannot be created or destroyed but only converted to other forms.

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Thermodynamics

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The study of energy transformations

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Second law of thermodynamics

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All energy transformations are inefficient because every reaction loses some energy to the surroundings as heat

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Entropy

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a measurement of randomnessthe more disordered a system is, the higher its entropy

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Metabolism

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The sum of the chemical reactions in a cell.

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Endergonic reaction

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Energy input because the products have more energy than the reactants; Energy "put into"; Potential Energy in Product > Reactant Energy; Example: Build complex molecules from simpler compounds

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Exergonic Reactions

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Energy is released; Energy "out of"; Potential energy in Potential Energy in Product < Reactant Energy. Example: Breakdown large, complex molecules into their smaller, simpler components

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Chemical equilibrium

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a reaction proceeds in both directions at the same rate.

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Oxidation-reduction ("redox") Reactions

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Reactions where energized electrons are transfered from from one molecule to another.

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Oxidation

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Reactions where there is the loss of electrons from a molecule, atom or ion. Oxidation reactions are Exergonic; Release energy; Go from complex molecules to simpler products.

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Reduction

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Reactions where there is a gain of electrons (plus any energy contained in the electrons); Reduction reactions are Endergonic; Require energy input; Go from simpler reactants to complex products.

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Electron transport chain

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An electron donor transfers an electron to the first protein in the chain. Like an electron bucket brigade or "shuttle". Energy lost along the way. Both photosynthesis and respiration use electron transport chains.

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ATP (Adenosine Triphosphate)

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Temporarily store much of the released energy from a chemical reaction; Holds energy from exergonic reaction (eat energy bar) it can be released into endergonic reactions, such as muscle contractions from released energy from ATP.

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hat is the composition of ATP?

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o It is a nucleotide o Nitrogen-containing base (Adenine) o Five-carbon sugar (Ribose) o Three Phosphate groups. o Releases energy when phosphate bonds break

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Coupled reactions

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Simultaneous reactions in which one provides the energy that drives the other

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Phosphorylation

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The transfer of a phosphate group from ATP to another molecule, causing the recipient to become energized or to change shape

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Enzymes

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Usually proteins; organic molecules that speed biochemical reactions by lowering the energy of activation; Recycled; Not consumed in reaction

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What do enzymes do ? What is their function?

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copy DNA, build proteins, digest food, recycle worn-out parts, catalyze oxidation-reduction reactions

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Cofactors

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Inorganic or organic substances that enzymes require to catalyze reactions; Either are reduced (gain electrons) or oxidized (lose electrons) during reaction; Recycled; Not consumed

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Negative feedback (Feedback inhibition)

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Reaction product temporarily shuts down its own synthesis whenever its levels rise

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Two types of negative feedback

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Non-competitive product binds to enzyme at a location other than active site; Competitive product binds to enzyme at active site

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Postitive feedback

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Rare; products stimulates its own further production

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What is it called competitive feedback?

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The product competes with the substrate to occupy the active site.

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What factors affect enzyme activity?

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Temperature, pH changes, Salt concentrations too high or low, Cofactors

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Is inside and outside the cell chemically the same?

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No. In eukaryotic cell, the inside of each organelle may be chemically quite different from the solution in the rest of the cell

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Concentration gradient

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No energy required; Difference in solute concentration between two neighboring regions

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Passive Transport

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Always required diffusion; spontaneous movement ( high concentration to lower concentration), No energy input required

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What can happen in phosphorylation?

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May energize the target molecule; May change the shape of the target moleculue

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Simple diffusion

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Substance finds something permeable; It moves across a membrane without the assistance of transport proteins; No protein required

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Osmosis

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Water diffuses across a selectively permeable membrane

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Tonicity

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The osmotic pressure or tension in solutions. Predicts whether cells will swell or shrinkIsotonic, hypotonic, hypertonic;

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Isotonic

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Solute concentration same inside and outside the cell; Water moves into and outside the cell at equal rates

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Hypotonic

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Solute concentration lower outside; greater inside

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Hypertonic

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Solute concentration higher outside; lower inside

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Turgor pressure

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The force of water pressing against the cell wall; Turgor pressure keeps plants erect and stiff; Loss of turgor pressure like in a hypertonic enviroment = wilted plant

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Facilitated diffusion

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Form of passive transport; Needs protein to assist in pulling substances across a membrane that is not so permeable

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Active Tranport

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Requires Energy; Requires transport protein to move substance against concentration gradient

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Sodium-Potassium pump

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protein that uses energy from ATP to transport Na+ out of cells and K+ into cells; Ions move from less concentration to more concentration

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Transport Vesicles

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Membranous vesicle carries materials into or out of a cell.

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Endocytosis

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Membrane engulfs a substance and draws it into the cell; Allows a cell to engulf Fluids and Large molecules and bring them into the cell.

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Types of endocytosis

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Pinocytosis, Phagocytosis, Receptor-mediated Endocytosis

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Pinoctyosis

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Cell engulfs Small amounts of fluids and disolved substances

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Phagocytosis

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Cell captures and engulf Large particles and debris, or even another Cell; Solid particles

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Receptor-mediated Endocytosis

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Occurs when the binding of a substance to a receptor protein triggers receptor-mediated endocytosis

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Exocytosis

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Vesicles fuses with cell membrane; releasing substances outside the cell; Uses vesicles to transport fluids and large particles out of cell

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What two important processes use the First Law of Thermodynamics?

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Photosynthesis and Cellular Respiration

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The more disorded a system is, the higher is its ___________________

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entropy

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Life is ____________ and complex.

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ordered

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________ in the universe is always increasing.

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Entropy

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What does equilibrium mean?

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It means the rates of formation are equal. It does not mean you have the same amount or equal products and reactans.

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Why do cells avoid equilibrium?

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They need metabolic processes to occur. If you have equilibrium, you have an accumulation of products and reactions will stop.

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Why do oxidation and reduction reactions occur simultaneously?

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Because electrons removed from one molecule during oxidation must join another molecule and reduce it.

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If one molecule gains electrons or is ____________, another molecule loses electrons or is ______________.

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reduced, oxidized.

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Which processes use the electron transport chain?

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Photosynthesis and respiration

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Why are electrons called shuttling "specialists" in the electron transport chain?

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Each protein accepts an electron from one molecule and passes it to another like a bucket brigade.

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Where is ATP produced or manufactured?

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Mitrochondria

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Where do you find most mitrochondria?

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With energy-hungry cells such as muscle and brain where a lot of energy is needed.

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_____________ is the "go-between" that links endergonic to exergonic reactions.

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ATP (ATP hydrolysis releases energy)

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Why is ATP called energy "currency for the cell?

answer

Just as you can use money to purchase a great variety of different products, all cells use ATP in many chemical reactions to do different kinds of work.

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What happens when cells low in ATP?

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Cells put some of their lipid and carbohydrate reserves to cellular respiration.

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Does the inside or interior of a cell have to be the same as its outside or exterior?

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No. The inside of each organelle in a eukaryotic cell may be chemically different from the solution in the rest of the cell

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