Catabolic and Anabolic Reactions

Metabolism

- The sum of all chemical reactions within a living organism.

Catabolism

Anabolism

Two classes of chemical reactions:

Catabolism

- an enzyme -regulated chemical reactions that releases energy

Catabolism

(Hydrolytic and exergonic)

Anabolism

- an enzyme-regulated energy requiring reactions

Enzymes

- serves as a biological catalyst that increases the reaction rate without raising the temperature in living system

Oxidoreductase

- Oxidation-reduction in which oxygen and hydrogen are gained or lost

Oxidoreductase

Ex: Cytochrome, Oxidase, Lactate, Dehydrogenase

Transferase

- Transfer of functional groups, such as amino group, acetyl group, or phosphate group

Hydrolase

Hydrolysis (addition of water)

Hydrolase

Ex: Lipase, Sucrase

Lyase

- Removal of groups of atoms without hydrolysis

Lyase

Ex: Oxalate decarboxylase, isocitrate lyase

Isomerase

- Rearrangement of atoms within a molecule

Isomerase

Ex: Glucose-phosphate isomerase, alanine racemase

Ligase

- Joining of two molecules (using energy usually derived from the breakdown of ATP)

Ligase

Ex: Acetyl-CoA synthetase, DNA ligase

Vitamin B1 (Thiamine)

- Part of coenzyme cocarboxylase, has many functions, including the metabolism of pyruvic acid

Vitamin B2 (riboflavin)

- Coenzyme in flavoproteins; active in electron transfer

Niacin (nicotinic acid)

- Part of NAD molecule⁺; active in electron transfer

Vitamin B6 (pyridoxine)

- Coenzyme in amino acid metabolism

Vitamin B12 (cyanocobalamin)

- Coenzyme involved in the transfer of methyl groups; active in amino acid metabolism

Riboflavin

Coenzyme of Vitamin B2 (cyanocobalamin)

Pantothenic Acid

- Part of Coenzyme A molecule; involved in the metabolism of pyruvic acid and lipids

Biotin

- Involved in carbon dioxide fixation reactions and fatty acid synthesis

Folic acid

- Coenzyme used in the synthesis of purines and pyrimidines

Vitamin E

- Needed for cellular and macromolecular syntheses

Vitamin K

- Coenzyme used in electron transport (naphtoquinones and quinones)

NAD+

Nicotinamide adenine dinucleotide

NADP⁺

Nicotinamide adenine dinucleotide phosphate

FMN

Flavin mononucleotide

FAD

Flavin adenine dinucleotide

Coenzyme A

= important in Krebs cycle

1. Changes in the amount of enzyme or substrate

2. Changes in temperature, pH or salt

3. Availability of necessary cofactors

4. Effects of Inhibitors

Biochemical reactions can be controlled by changes in enzyme activity, which can be influenced in several ways:

more product

more enzyme and more substrate = ?

Changes in temperature, pH or salt

can affect enzyme structure, hence its activity

non-protein factor

some enzymes don’t work w/o a

Effects of Inhibitors

molecules that bind to enzymes & reduce their activity

Temperature, pH, Substrate

Factors Affecting Enzymes

Temperature

- reactions occur more rapidly as temperature rises

heat

as long as enzyme is active (____ can denature enzymes)

pH

- enzyme structure depends on ?

R groups or protein structure

* pH affects charge of

Substrate

- reactions occur more rapidly as substrate rises

Saturation

occurs when substrate is high enough

Competitive inhibitors

- fill the active site of an enzyme and compete with the normal substrate for the active site

- The inhibitor’s shape and chemical structure are similar to the normal substrate

- it does not undergo any reactions to for products

- binds irreversibly or reversibly

Sulfa Drugs (Sulfanilamide)

competitive inhibitors for PARA essential to synthesize folic acid

paraaminobenzoic acid

PARA

 Noncompetitive inhibitors

- the binding causes the active site to change its shape, making it non-functional

allosteric inhibition

Noncompetitive inhibitors interact with one another part of the enzyme (allosteric site) rather than the active site

cyanide and fluoride

called enzyme poisons because they permanently inactive enzymes

feedback inhibition or end-product inhibition

Noncompetitive inhibitors Plays a role in a kind of biochemical control

Feedback Inhibition

is a control mechanism that stops the cell from making more of a substance than it needs and thereby wasting chemical resources

Feedback Inhibition

Generally acts on the first enzyme in a metabolic pathway and the product of the first enzymatic reaction in the pathway is not synthesized

Oxidation

removal of electrons from an atom or molecule – produces energy

Reduction

gain of electrons

Oxidation-Reduction or Redox Reactions

- oxidation reaction paired with a reduction reaction

Oxidation Reduction

cell use them in catabolism to extract energy from nutrient molecules

Dehydrogenation

– loss of hydrogen atoms in biological oxidations

Substrate-Level Phosphorylation

ATP is usually generated when a high-energy P is directly transferred from a phosphorylated compound (substrate) to ADP.

Oxidative Phosphorylation

electrons are transferred from organic compounds to one group of electron carriers (usually to NAD⁺ and FAD), the electrons are passed through a series of different electron carriers to molecule of oxygen (O2) or other oxidized inorganic and organic molecules

plasma membrane of prokaryotes and the inner mitochondrial membrane of eukaryotes

Oxidative Phosphorylation occurs in the

chemiosmosis

The transfer of electrons from one electron carrier to the next releases energy, some of which is used to generate ATP from ADP through a process called

Photophosphorylation

Occurs only in photosynthetic cells, which contains light-trapping pigments such as chlorophylls

converting light energy to the chemical energy of ATP and NADPH, which in turn are used to synthesize organic molecules

Phosphorylation starts this process by

photosynthesis, organic molecules, especially sugars

synthesized with the energy of light from the energy-poor building blocks carbon dioxide and water

metabolic pathways

A series of enzymatically catalyzed chemical reactions called ____ store energy in and release energy from organic molecules

Carbohydrate Catabolism

The breakdown of carbohydrate molecules to produce energy

Glucose

 is the most common carbohydrate energy source used by cells

Cellular respiration

glucose is completely broken down

Fermentation

glucose is partially broken down

Glucose

The oxidation of glucose to pyruvic acid with the production of (2) ATP and energy containing (2) NADH

Krebs Cycle

- The oxidation of acetyl CoA to carbon dioxide, with the production of some ATP, energy containing NADH, and another reduced electron carrier, FADH2

Electron Transport Chain

NADH and FADH2 are oxidized contributing the electrons they have carried from the substrates to a cascade oxidation-reduction reaction involving a series of additional electron carriers

last step

In ETC, Most ATP is generated at what step?

Glycolytic Pathways (Glycolysis)

1. Partial oxidation of glucose to form pyruvic acid

2. A small amount of ATP is made

3. A small amount of NAD is reduced to NADH

Glycolytic Pathways (Glycolysis)

Net Gain: 2 ATP & 2 NADH

Embden-Meyerhoff-Parnas Pathway

classic glycolysis found in almost all organisms

Pentose phosphate pathway

AKA Hexose monophosphate shunt

Pentose phosphate pathway

Operates simultaneously with glycolysis and provides a mean for the breakdown of five-carbon sugars (pentose) as well as glucose

Pentose phosphate pathway

Produces important intermediate pentoses used in the synthesis of nucleic acids, glucose from carbon dioxide in photosynthesis and certain amino acids

reduced coenzyme (12) NADPH from NADP⁺

Pentose phosphate pathway is an important producer of

a net gain of one molecule of ATP for each molecule of glucose oxidized

Pentose phosphate pathway Yields ____

Entner-Doudoroff pathway

For each molecule of glucose, it produces 2 molecules of NADPH and one molecule of ATP for use in biosynthetic reactions

Bacteria that have the enzyme for the Entner-Doudoroff pathway

can metabolize glucose without either glycolysis or the pentose-phosphate pathway

Phosphoketolase Pathway

Found in Bifidobacterium and Leuconostoc

Pentose phosphate pathway

Bacillus subtilis, E.coli, Leuconostoc meselteroides, and Entrerocococcus faecalis

Entner-Doudoroff pathway

- Found in Pseudomonas and related genera

      - Rhizobium and Agrobacterium

Glycolysis

Produce energy from glucose

1. Respiration                      2. Fermentation

microbes use 2 general processes:

glycolysis

Respiration and Fermentation starts with ____ but follows different subsequent pathway

Respiration

- Nutrients are converted into useful energy in a cell to produce ATP

Fermentation

- metabolic process converting sugars to acids, gases, alcohols

O₂

in Aerobic Respiration, __ is the final acceptor

up to 38 per glucose molecule

in Respiration (respiratory pathway) A lot of additional ATP are made which is

1. Preliminary reactions and the Krebs Cycle (TCA or Citric Acid Cycle)

- Acetyl CoA combines with citric acid until it forms oxaloacetic acid and the cycle repeats

1. Preliminary reactions and the Krebs Cycle (TCA or Citric Acid Cycle)

Net gain: 2 ATP, 3 NADH, 1 ubiquinol

38 - 2

In Eukaryotes how many ATP

energy for the transport of NADH from the cytoplasm to the mitochondria

What happens to the 2 ATP in eukaryotes?

·         biochemical identification

Fermentation pathways are useful as tools in