Chapter 8

Front 1

The Metabolism of Microbes:

Metabolism

Back 1

All chemical and physical workings of a cell.

* two types of chemical reactions:

- Catabolism, Anabolism.

Front 2

Catabolism:

Back 2

degradative; breaks the bonds of larger molecules forming smaller molecules; releases energy.

* Release of energy cellular respiration.

Front 3

Anabolism:

Back 3

biosynthesis, process that forms larger

macromolecules from smaller molecules; requires energy input.

* Photosynthesis requires energy.

* ATP: cellular gas.

Front 4

Enzymes:

Back 4

* Enzymes are biological catalyst that increase the rate of a chemical reaction by lowering the energy of activation (the resistance to a reaction)

- example: two molecules - enzymes will alter the structure to fit.

* 2 active sites > substrates.

example: light a fire, match - adds energy to get a lot of energy.

* The enzyme is not permanently altered in the reaction.

* Enzyme promotes a reaction by serving as a physical site for specific substrate molecules to position.

Front 5

Enzymes Characteristics:

Back 5

- Non-protein cofactors

- Activation energy

- Metabolic reactions

- Active site

- Substrates

- Feedback mechanisms

Front 6

Enzyme Structure:

Back 6

* Simple enzymes - consist of protein alone.

* Conjugated enzymes or holoenzymes - contain protein and non-protein molecules.

- Apoenzyme: protein portion

- Cofactors: non-protein portion

* Metalic cofactors: iron, copper, mg.

* Coenzymes: organic molecules: vitamins

Front 7

Apoenzymes: Specificity and the Active site

Back 7

* Exhibits primary, secondary, tertiary and some quaternary structure (importance of these structural aspects) **important in enzymes.

* Site for substrates binding is active site, or

catalytic site.

- temp. is critical for enzyme or pH is important with proteins (your body)

- very specific.

- (ase) enzyme.

Front 8

Apoenzymes:

Back 8

* A temporary enzyme- substrate union occurs when substrate moves into active site - induced fit

* Appropriate reaction occurs; product is formed and released.

- Temporary connection, do not change

permanently.

Front 9

Cofactors: Supporting the work of Enzymes

Back 9

* Micronutrients are needed as cofactors.

* Cofactors act as carriers to assist the enzymes in its activity.

- Non-protein portion.

example: vitamin.

***Know what a cofactor is and what it does.

Front 10

Locations of enzyme Action: Exoenzymes

Back 10

- transported extracellularly, where they break down large food molecules or harmful chemical.

Front 11

Locations of enzyme action: Endoenzymes

Back 11

- retained intracellularly and function there work inside cells.

- Most enzymes are endoenzymes.

Front 12

Regularity of Enzyme Action:

Constitutive enzymes

Back 12

* always present, always produced in equal amounts or at equal rates, regardless of the amount of substrate.

Front 13

Regularity of Enzyme Action:

Regulated enzymes

Back 13

* no constantly present; production is turned on (induced) or turned off (repressed) in response to changes in the substrate concentration.

Front 14

Synthesis Reaction (Condensation reactions)

Back 14

- anabolic reactions to form covalent bonds between smaller substrate molecules, require ATP, release one molecule of water for each bond formed.

* loses a H+ off one and OH of another. those two form water, lose water. Building.

* glycosidic bond.

Front 15

Hydrolysis reaction: (hydrating)

Back 15

- catabolic reactions that break down substrates into small molecules; requires the input of water to break bonds.

* water is back in.

* peptide bond.

Front 16

An enzyme

Back 16

may be active extracellularly

Front 17

Sensitivity of Enzymes to their environment

Back 17

* Activity of an enzyme is influence by the cells environment hugely.

* Enzymes operate under temperature, pH,and osmotic pressure of organisms habitat.

* When enzymes are subjected to changes in organism's habitat they become unstable.

- Labile: chemically unstable enzyme

- Denaturation: weak bonds that maintain the shape of the apoenzyme are broken.

*** breaking bonds.

Front 18

Direct Controls on the Actions of Enzymes:

Competitive inhibition

Back 18

substances that resembles the normal substrate competes with the substrate for the active site.

*competition

Front 19

Direct Controls on the Actions of the Enzymes:

Noncompetitive inhibition (allosteric)

Back 19

enzymes are regulated by the binding of molecules other than the substrate away from the active site.

* changes shape of active site

- Enzyme repression: inhibits at the genetic level by controlling synthesis of key enzymes.

- Enzyme induction: enzymes are made only when suitable substrates are present. induced by the substrate.

Front 20

Enzyme Characteristics*****KNOW

Back 20

* Composed mostly of protein, may require nonprotein cofactors

* act as organic catalysts to speed up the rate of cellular reactions.

* lower the activation energy required for a chemical reaction to proceed

* enable metabolic reactions to proceed at a speed compatible with life.

* have unique characteristics such as shape, specificity, and function.

* Provide and active site for target molecules called substrates.

* Are much larger in size than their substrate

* Associate closely with substrates but do not become integrated into the reaction products.

* are not used up or permanently changed by the reaction.

* can be recycled and function in extremely low concentrations

* are greatly affected by temperature and pH

* Can be regulated by feedback and genetic mechanism.

Front 21

Biological Oxidation and Reduction: Redox

Back 21

- Always occur in pairs

* There is an electron donor and electron acceptor which constitutes a redox pair.

* Process salvages electrons and their energy.

* Released energy can be captured to phosphorylate ADP or another compound.

- lose electrons > Oxidation

- gains electrons > Reduced

Front 22

***Electron and Proton Carriers***

Back 22

* repeatedly accept and release electrons and

hydrogen to facilitate the transfer of redox energy.

* Most carriers are coenzymes:

-NAD, FAD, NADP, coenzyme A, and

compounds of the respiratory chain.

Front 23

If a molecule has been reduced during a reaction,

it has

Back 23

Gained electrons and hydrogen

Front 24

Adenosine Triphosphate: ATP

Back 24

* Metabolic "currency"

* Three part molecule consisting of

- adenine - a nitrogenous base

- Ribose - a 5 -carbon sugar

- 3 phosphate groups

* Removal of the terminal phosphate releases

energy.

* ATP utilization and replenishment is a constant cycle in active cells.

***gas of cell, constant cycle.

Front 25

Formation of ATP:

ATP can be formed by 3 different methods.

Back 25

1) Substrate-level phosphorylation - transfer of phosphate group from phosphorylation compound (substrate) directly to ADP.

2) Oxidative phosphorylation - series of redox.

***add 3rd phosphate group-building ATP

3) Photophosphorylation - ATP is formed utilizing the energy of sunlight. **green plants.

*****1 & 2 for us.

Front 26

Bioenergetics

Back 26

Study of the mechanisms of cellular energy release

* includes catabolic and anabolic reactions

* Primary catabolism (breaking down) of fuels (glucose) proceeds through a series of three coupled pathways.

1) Glycolysis

2) Kreb's cycle CO2 + H2O

3) Respiratory chain, electron transport

***all cellular respiration.

***15 steps divided by 3 steps moving electrons to right place for your cellular battery.

Front 27

Metabolic Strategies: 3 ways

Back 27

* Nutrient processing is varied, yet in many cases is based on three catabolic pathways that convert glucose to CO2 and gives off energy.

1) Aerobic respiration - glycolysis, the Kreb's cycle respiratory chain; oxygen is the final electron

acceptor. ***us, cannot live w/o O2.

2) Anaerobic respiration - glycolysis, the Kreb's cycle respiratory chain; molecular oxygen is not the final electron acceptor.

3) Fermentation - glycolysis, organic compounds are the final electron acceptors. (Beer, wines)

* (key thought here - what is the major difference between the three mechanisms above? Which ones can humans carry out? which ones can various bacteria carry out?

Front 28

(key thought here - what is the major difference between the three mechanisms above? Which ones can humans carry out? which ones can various bacteria carry out?

Aerobic vs anaerobic vs fermentation.

Back 28

* Aerobic respiration - cannot live without O2 (-); humans. final electron acceptor is oxygen.

* Anaerobic respiration - can live without O2 (+); bacteria, final electron acceptor is sulfate, nitrate, or nitrite.

* Fermentation - require O2 (-)bacteria. final electron acceptor is organic compound. (production of alcohol, vinegar, and certain industrial solvents relies upon fermentation.)

Front 29

Overview of Catabolic pathways

Back 29

Glycolysis and Krebs cycle involve breaking down the 6-carbon glucose;

Electron transport involves moving energy to the right place for use.

Front 30

Aerobic Respiration

Back 30

* Series of enzyme-catalyzed reactions in which electrons are transferred from fuel molecules

(glucose) to oxygen as a final electron acceptor.

- Glycolysis - glucose (6C) is oxidized and split into 2 molecules of pyruvic acid (3C), NADH is

generated.

- Krebs Cycle (tricarboxylic acid cycle) - processes pyruvic acid and generates 3 CO2 molecules NADH and FADH2 are generated.

- Electron transport chain - accepts electrons from NADH and FADH; generates energy through sequential redox reactions called oxidative phosphorylation.

Front 31

Electron Transport and Oxidative Phosphorylation

Back 31

* Final processing of electrons and hydrogen and the major generator of ATP.

* chain of redox carriers that receive electrons from reduced carriers (NADH and FADH2)

* ETS shuttles electrons down the chain, energy is released and subsequently captured and used by ATP synthase complexes to produce ATP - Oxidative phosphorylation.

Front 32

The formation of ATP and Chemiosmosis

Back 32

* Chemiosmosis- as the electron transport carriers shuttle electrons, they actively pump hydrogen ions (protons) across the membrane setting up a gradient of hydrogen ions- proton motive force (similar to the battery in your flashlight) * ***energy released

* example: charging battery-charging phase, driving energy/electrons across membrane. Big gradient > get energy released.

- Hydrogen ions diffuse back through the ATP synthase complex causing it to rotate, causing a 3-D change resulting in the production of ATP

Front 33

The Terminal Step

Back 33

* oxygen accepts 2 electrons from the ETS and then picks up 2 hydrogen ions from the solution to form a molecule of water. Oxygen is the final electron acceptor.

2H+ + 2e + 1/2O2 > H2O

Front 34

What part of aerobic respiration releases CO2?

Back 34

Krebs Cycle

Front 35

Anaerobic Respiration

Back 35

- Functions like aerobic respiration except it utilizes oxygen containing ions, rather than free oxygen, as the final electron acceptor

- Nitrate (NO3) and nitrite (NO2)

- Most obligate anaerobes use the H+ generated during glycolysis and the Kreb's cycle to reduce some compound other than O2.

Front 36

Fermentation

Back 36

* Incomplete oxidation of glucose or other carbohydrates in the absence of oxygen

* uses organic compounds as terminal electron

acceptors.

* Yields a small amount of ATP

* Production of ethyl alcohol by yeasts acting on glucose.

* formation of acid, gas, and other products by the action of various bacteria on pyruvic acid.

Front 37

Aerobic respiration

Back 37

pathway: Glycolysis, Krebs cycle, electron transport.

final electron acceptor: O2

Products: ATP, CO, H2O

Primary pathway found in: Aerobes, facultative

anaerobes.

Front 38

Anaerobic Metabolism & Fermentation

Back 38

pathway involved: glycolysis

final electron acceptor: organic molecules

products: ATP, CO2, ethanol, lactic acid

primary pathway found in: facultative, aerotolerant, strict anaerobes.

Front 39

Respiration

Back 39

pathways involved: Glycolysis, Krebs cycle, electron transport.

final electron acceptor: various inorganic ions, (NO3, SO4, CO3)

products: CO2, ATP, organic acids, H2S, CH4, N2.

Front 40

Biosynthesis and Crossing Pathways of Metabolism

Back 40

* Many pathways of metabolism are bi-directional or amphibolic. (Framework)

Front 41

Photosynthesis: The Earth's Lifeline (2 stages)

Back 41

* The ultimate source of all the chemical energy in cells comes from the sun.

6CO2 + 6H2O > C6H12O6 + 6O2

sugar & oxygen

Front 42

Photosynthesis

Back 42

- occurs in 2 stages

- Light-dependent - photons are absorbed by chlorophyll, carotenoid, and phycobilin pigments.

* Water split by photolysis, releasing O2 gas and provides electrons to drive photophosphorylation.

* Released light energy used to synthesize ATP and NADPH

- energy used to build glucose.

Front 43

The main job of chloroplast pigments during photosynthesis is to:

Back 43

fix carbon dioxide into large organic molecules

Front 44

light-independent

Back 44

dark reaction - calvin cycle - uses ATP to fix CO2 to ribulose - 1, 5-bisphosphate and convert it to glucose.

Front 45

light-dependent

Back 45

the trapping of light with a photosensitive pigment, such as chlorophyll and converting the light energy into chemical energy in the form of ATP and NADPH; and splitting of water molecules with the release of oxygen gas.