Unit 2

Kinetic energy

energy of motion

Potential energy

stored energy

Mechanical energy

sum of kinetic and potential energy

Chemical energy

food we eat

Law of conservation of energy

energy cannot be created or destroyed; can change forms

Law of entropy

when energy is changed there is a loss of energy; nothing is 100% efficient

Energy transformations

processes occurring in cells; every process increases entropy

Free energy

amount of energy available to perform work

Exergonic reaction

products have less free energy than reactants (release energy) (spontaneous)

Endergonic reactions

products have more free energy than reactants (require energy input) (nonspontaneous)

Adenosine Triphosphate (ATP)

high energy compound used to drive metabolic reactions; constantly generated from adenosine diphosphate (ADP)

ATP compound

adenine + ribose (adenosine); and three phosphate groups

Coupled reactions

energy released by exergonic reactions is captured in ATP; used to drive endergonic reactions

Enzymes

protein molecules function as catalysts

Substrates

reactants of enzymatically catalyzed reaction; products of earlier reaction become ??? of later reactions; form metabolic pathways

Induced fit model

model that shows how enzymes are induced to undergo a slight alteration to achieve optimum fit for substrates

Degradation

enzyme complexes with single substrate molecule; substrate is broken into two product molecules, released

Synthesis

enzyme complexes with two substrate molecules; join together and released as single molecule

Energy of activation

prevents molecules from spontaneously degrading in cell

Enzyme operation

??? happens by lowering energy of activation; accomplished by bringing substrates into contact with one another; influences rate of reaction and why enzymes are catalysts of chemical reactions

Substrate concentration

enzyme activity increases with ??? due to more frequent collisions between substrate molecules and the enzyme

Denature

can happen when temperature is too hot for enzyme

Cells with enzymes

can regulate presence/absence; regulate concentration; activate/deactivate some enzymes

Enzyme cofactors

molecules required to activate enzyme

Coenzymes

nonprotein organic molecules; (ex: vitamins)

Inhibitor

binds to enzyme and decreases its activity

Competitive inhibition

binds to active site and compete with one another (substrate and inhibitor)

Noncompetitive inhibition

inhibitor does not bind at active site but allosteric site

Photosynthesis

chloroplast captures solar energy and use it to convert water and carbon dioxide to carbohydrate; carbon dioxide is reduced, and water oxidized, energy provided by solar energy

Cellular respiration

mitochondria oxidize carbohydrate and use released energy to build ATP; consumes oxygen and produces carbon dioxide; glucose oxidized, and oxygen reduced

Photosynthesis and cellular respiration cycle

from sun to photosynthesis to cellular respiration, both chloroplast and mitochondria involved in redox cycle; CO2 reduced in PS and carb oxidized in CR

Solar energy

important for all life on earth

Photosynthetic organisms

transform solar energy into chemical energy of carbohydrates (algae, plants, cyanobacteria)

Photosynthesis

process that captures solar energy, transform solar energy into chemical energy, energy ends up stored in a carbohydrate; takes place in green portions of plants; CO2 reduced, and water oxidized

CO2 + H2O --solar energy--> C6H1206 + O2

photosynthesis equation

Stomata

opening in leaves that carbon dioxide can enter through

Thylakoid membranes

contain chlorophyll and other pigments that can absorb the solar energy that drive photosynthesis

Stroma

place where CO2 combines with H2O to form sugar/glucose

Light reactions

takes place only in presence of light; energy-capturing reactions; chlorophyll absorbs solar energy and energizes electrons that move down an electron transport chain; pumps H+ into thylakoids; also used to make ATP from ADP and NADPH from NADP+

Calvin cycle reactions

takes place in stroma; CO2 reduced to carbohydrate; reactions use ATP and NADPH to produce carbohydrate

Carotenoids

accessory pigments which absorb light in the violet-blue-green range and reflect yellow and orange light

Pigment complex

photosystem that helps collect solar energy (antenna)

Photosystems

located in thylakoid membrane; noncyclic and cyclic pathways, both produce ATP but noncyclic pathway also produces NADPH

Noncyclic pathway

thylakoid membrane; two photosystems' PS I (P700) and PS II (P680) (captures light energy); begins with photosystem II

NADPH production

electron ejected from chlorophyll a (reaction center); travels down ETC to PS I replaced electron from water (split to form O2 and H+); causes H+ to accumulate in thylakoid chambers (lumen/inside); H+ gradient is used to produce ATP; PS I captures light energy and ejects an electron; electron is transferred permanently to molecule of NADP+ which causes ???

PS II (P680)

consists of a pigment complex and electron acceptors; receives electrons from the splitting of water (photolysis); oxygen released as a gas

Electron transport chain (ETC)

consists of cytochrome complexes and plastoquinone; carries electrons between PS II and PS I; pumps H+ from stroma to thylakoid space

PS I (700)

has pigment complex and electron acceptors; adjacent to enzyme that reduces NADP+ to NADPH

ATP synthase complex

has a channel for H+ flow; H+ flow through the channel drives ATP synthase to join ADP to each other (photophosphorylation)

Chemiosmosis

tied to establishment of H+ gradient; each time water is oxidized two H+ remain in thylakoid space; energy from ETC moves protons from stroma to thylakoid space; flow of H+ back across thylakoid membrane energizes ATP synthase

C3 photosynthesis

utilizes atmospheric carbon dioxide to produce carbohydrates

Carbon dioxide fixation, carbon dioxide reduction, RuBP regeneration

three stages of C3 photosynthesis (in order)

Fixation of carbon dioxide

CO2 is attached to 5-carbon RuBP by the enzyme RuBP carboxylase; results in a 6-carbon molecule, splits into 2 3-carbon molecules (3PG), accelerated by RuBP carboxylase (Rubisco)

RuBP

ribulose-1, 5-bisphosphate

3PG

3-phosphoglycerate

BPG

1,3-bisphosphoglycerate

G3P

glyceraldehyde-3-phosphate

Reduction of carbon dioxide

3PG is reduced to BPG, BPG is reduced to G3P; each stage uses electrons and energy (ATP-> ADP + P) (NADPH-> NADP+)

Regeneration of RuBP

RuBP used in CO2 fixation must be replaced; every 3 turns of Calvin cycle: 5 G3P (3-carbon molecule) are use to make 3 RuBP (5-carbon molecule), uses 3 ATP (turns into 3 ADP +P)

Importance of Calvin Cycle

G3P can be converted to many other molecules

G3P molecules

fatty acids and glycerol to make oils, glucose phosphate (simple sugar), fructose (with glucose=sucrose), starch and cellulose, and amino acids

C3 photosynthesis

uses RuBP carboxylase to fix CO2 to RuBP in the mesophyll cells

Photorespiration

stomata must close to avoid wilting; CO2 decreases and O2 increases; O2 starts combining with RuBP, leading to production of CO2; happens in hot/dry climates

C4 plants

fix CO2 to PEP (C3 molecule); results in oxaloacetate (C4 molecule); net productivity is about 2-3 times greater than C3 plants

crassulacean-acid metabolism

CAM

CAM plants during night

plants fix CO2; form C4 molecules (stored in large vacuoles)

CAM plant during daylight

NADPH and ATP; stomata closed for water conservation; C4 molecules releases CO2 to Calvin cycle

C4 adaptations

high light/temperatures; limited rainfall

C3 adaptations

cold (below 25C); high moisture

CAM adaptations

extreme aridity

Cellular respiration

cellular process that breaks down nutrient molecule produced by photosynthesizes with that concomitant production of ATP; aerobic process (consumes oxygen and produces CO2)

C6H12O6 + 6O2 ---> 6 CO2 + 6 H2O + energy

cellular respiration equation

NAD+

Nicotinamide adenine dinucleotide; coenzyme of oxidation-reduction

FAD

flavin adenine dinucleotide; also coenzyme of oxidation-reduction; accepts 2 electrons and 2 hydrogen ions to become FADH2

Glycolysis; Preparatory reaction; Citric acid cycle; ETC

4 stages of cellular respiration (in order)

Glycolysis

step 1; breakdown of glucose into two molecules of pyruvate; occurs in cytoplasm; ATP formed; does not utilize oxygen (anaerobic); occurs in cytoplasm outside mitochondria; 10 reactions (own enzyme)

Preparatory (prep) reaction

step 2; connects glycolysis to citric acid cycle; both molecules of pyruvate are oxidized and enter the matrix of mitochondria; converted to a 2-carbon acetyl group; electron energy is stored in NADH; 2 carbons released as CO2; occurs twice per glucose molecule

Citric acid cycle

step 3; also called Krebs cycle; occurs in matrix of mitochondrion; turns twice per glucose molecules; begins with addition of C2 acetyl group to C4 (oxaloacetate) forming C6 molecule (citric acid)

Electron transport chain (ETC)

step 4; series of carriers on the cristae of mitochondria and aerobic prokaryotes on plasma membrane; extracts energy from NADH and FADH2; passes electrons from high to low energy states; produces ATP by oxidative phosphorylation; pumps H+ from matrix into intermembrane space of mitochondrion; 32-34 ATP

Energy-Investment steps

two ATP are used to activate glucose; glucose splits into two G3P molecules (glycolysis)

Energy harvesting steps

oxidation of G3P occurs by removal of electrons and hydrogen ions; 2 electrons and one hydrogen ion are accepted NAD+ resulting in 2 NADH (glycolysis)

substrate-level ATP synthesis

4 ATP are produced; enzyme passes a high-energy phosphate to ADP

Inputs of Glycolysis

6C glucose; 2 NAD+; 2 ATP; 4 ADP + 4 P

Outputs of Glycolysis

2 (3C) pyruvates; 2 NADH; 2 ADP; 4 ATP (2 ATP net gain)

Pyruvate

pivotal metabolite in cellular respiration; if O2 is available ??? enters mitochondria for aerobic respiration

Fermentation

anaerobic process that reduces pyruvate to either lactate or alcohol and CO2; NADH transfers its electrons to pyruvate

Alcoholic fermentation

carried out by yeasts; produces carbon dioxide and ethyl alcohol (used in production of alcoholic spirits and breads)

Lactic acid fermentation

carried out by certain bacteria and fungi, produces lactic acid (lactate) (used in cheese, yogurt, and sauerkraut)

Advantages of fermentation

provides quick burst of ATP energy for muscular activity

Disadvantages of fermentation

toxic to cells; lactate changes pH and causes muscles to fatigue; yeast die from alcohol they produce

Efficiency of fermentation

2 ATP produced per glucose

Inputs of Prep reaction

2 pyruvates (from glycolysis) + 2 CoA (2-carbon acetyl group w/ coenzyme A) (2 NAD+)

Outputs of Prep reaction

2 acetyl-CoA + 2 CO2 (2 NADH)

Inputs of Citric acid cycle

2 (2c) acetyl groups; 6 NAD+; 2 FAD; 2 ADP +2 P

Outputs of Citric acid cycle

4 CO2; 6 NADH; 2 FADH2; 2 ATP

Cytochrome

proteins with heme groups with central iron atoms

Oxygen final electron acceptor

combines with hydrogen ions to form water

Fate of hydrogens

hydrogens from NADH deliver enough energy to make 3 ATPs; from FADH2 have only enough for 2 ATPs; "spent hydrogens combine with oxygen

ATP synthase

allows H+ to flow down its gradient

Chemiosmosis

ATP production is linked to establishment of the H+ gradient