© 2009 FIDM/The Fashion Institute of Design & Merchandising

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Chapter 5 – The Working Cell

ENERGY AND THE CELL 1. Energy – capacity to make things happen, move or do work

a. Kinetic Energy = energy in motion b. Potential Energy = stored energy

Chemical energy – the potential energy in molecules 2. Laws of Thermodynamics (study of energy transformations)

a. 1st Law = law of energy conservation; energy can be transferred or transformed but cannot be created or destroyed

EX. Electrical – light; sunlight – chemical – heat; chemical – light (firefly) b. 2nd Law = one-way flow of energy; total energy in universe is spontaneously

flowing from forms of higher energy to lower energy content; heat en (disordered form of en, cannot be reused); energy conversions reduce order of universe and increase its entropy

EX. Sunlight – plant (chemical en)– consumer (chem. en and heat loss) 3. Chemical Reactions in Cell

a. endergonic reactions – requires input of energy to make potential energy EX. Photosynthesis (requires sunlight)

b. exergonic reactions – release energy EX. Burning wood; Cellular respiration (slow burn)-releases en from glucose as chemical en (ATP) and heat

c. cellular metabolism – cell’s capacity to acquire energy and to use it to build, break apart, store and release substances in controlled ways

d. Energy coupling – use of energy from exergonic reactions to drive essential endergonic reactions; ATP molecules are key

4. ATP – shuttles chemical energy an drives cell work a. ATP -------ADP + P + energy (exergonic reaction)

Hydrolysis (H2O) b. Phosphorylation – transfer of P to another molecule (ATP energizes other

molecules by phophorylating them) c. Cellular work: 3 types – chemical, mechanical, transport d. ATP is regenerated (10 million ATP molecules/sec)

ENZYMES

1. protein molecule that functions as a biological catalyst ( i.e., speed up cell’s

chemical reactions) by lowering energy of activation 2. specific enzyme catalyzes each cellular reaction (shape and structure affect function; environmental conditions can affect shape: temp, salt, pH)

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3. Cofactors – non-protein helpers of enzymes – coenzyme if organic (vitamins); and inorganic (trace elements, zinc, iron, copper, minerals) 4. Enzyme Inhibitors – regulates metabolism, prevents too much product; destructive (poisons) or constructive (drugs to prevent disease)

MEMBRANE STRUCTURE AND FUNCTION 1. cell organelle membranes contain enzymes 2. plasma membrane – selective permeability

a. Phospholipids form membrane structure (outer layer attracts water, inner repels) b. Fluid Mosaic structure – proteins embedded in phospholipids layers; proteins

help move molecules across membrane 3. Passive Transport – diffusion across a membrane; no work/energy involved

a. Facilitated diffusion – transport proteins help speed up diffusion b. Osmosis – diffusion of water (not solute); isotonic, hypertonic, hypotonic (p.83)

Osmoregulation- cell controls water balance: flaccid, turgid, plasmolysis 4. Active Transport – requires energy – ATP

a. sodium-potassium pump b. exocytosis – transport of large molecules out of cell c. endocytosis – transport of large mol into cel

CHLOROPLASTS AND MITOCHONDRIA 1. make energy available for cellular work 2. photosynthesis – converts sunlight energy to chemical energy (glucose) in the

chloroplast 3. cellular respiration - mitochondria use this chemical en stored in glucose to make

ATP by taking in oxygen