Chapter 5&6 lecture flashcards
Cells must accomplish 2 fundamental tasks to grow
- Synthesize new components = ANABOLISM
- Biosynthesis - Harvest energy = CATABOLISM
The sum total of chemical reactions of biosynthesis and energy-harvesting is termed?
Metabolism
Metabolism has 2 components
1) Catabolism
– Degradative reactions
– Produce energy from breaking down molecules
2) Anabolism
– Synthesis of cell components
– Require energy input
* Anabolic reactions utilize the energy produced from catabolic reactions
Metabolic pathways occur in sequence of chemical reactions
- Starting compound is converted to intermediate molecules and end products.
- Intermediates and end products can be used as precursor metabolites
- Metabolic pathways employ critical components to complete processes:
Enzymes
ATP
Chemical energy source
Electron carriers
Precursor metabolites
What is the role of enzymes?
– Enzymes facilitate each step of metabolic pathway
– They are generally proteins and act as catalysts
* Favors (does not accelerate) conversion of substrate to product
– Catalyze reactions by lowering activation energy
* Energy required to initiate a chemical reaction
Enzyme inhibitors
– Competitive inhibitors bind active site
– Allosteric inhibitors bind elsewhere causing shape of enzyme to change
Role of ATP
– Adenosine triphosphate (ATP) * Energy currency of cell – Negatively charged phosphate groups attached to adenosine molecule * Negative charges of phosphate repel each other & create unstable bond that is easily broken releasing energy – ATP created by 3 mechanisms: Substrate phosphorylation Oxidative phosphorylation Photophosphorylation
Substrate phosphorylation uses?
Chemical energy to add phosphate ion to molecule of ADP
Oxidative phosphorylation uses?
Energy from proton motive force to add phosphate ion to ADP
Photophosphorylation ultilizes?
Radiant energy from sun to convert ADP to ATP
Role of chemical energy source
- Energy source: Compound broken down to release energy, variety of compounds available, glucose most common organic molecule
Harvesting energy requires series of couples reactions
Oxidation-reduction reactions
Oxidation-reduction reactions
– Electrons transferred from one substance to another
* Compounds that LOSE electrons are oxidized (termed electron donor)
* Compounds that GAIN electrons are reduced (termed electron carrier)
– In reactions, electrons are removed
* Protons often follow, generally in the form of H+ ion
– H+ ion has one proton and no electron
Three different types of electron carriers
1) Nicotinamide adenine dinucleotide (NAD+)
2) Flavin adenine dinucleotide (FAD)
3) Nicotinamide adenine dinucleotide phosphate (NADP+)
Reduced forms of electron carriers represents?
Reducing power. - due to usable energy in bonds Reduced forms are: – NADH – FADH2 – NADPH
Precursor metabolites are?
– Intermediate products produced in catabolic pathways
– Used in anabolic pathways
* Serve as raw materials for construction of macromolecules
The key central metabolic pathways are?
– Glycolysis – Tricarboxylic acid cycle (TCA) – Electron Transport Chain – Fermentation – Pentose phosphate pathway
Central (metabolic) pathways are amphibolic and provide?
– Energy (ATP)
– Reducing power
– Precursor metabolites
Electrons move from one carrier to another, eventually to a?
Terminal e- acceptor
This chain (electron transport chain) allows protons to be pumped across the cell membrane of prokaryotes, a?
PROTON GRADIENT
Proton gradient provides energy to?
Phosphorylate ADP -> ATP
Respiration generates a?
Proton gradient
– Produces ATP by oxidative phosphorylation
– Used to power flagella and some active transport
Aerobic respiration
– Final electron acceptor is O2 (yields H2O)
– Uses Krebs (TCA) cycle
– More ATP generated = most effective
Anaerobic respiration
Anaerobic respiration
– Final electron acceptor is not Oxygen
– Uses modified Krebs (TCA) cycle, generating less reducing power
– Less ATP generated = less effective
Fermentation is?
1) For cells that cannot respire
2) Do not oxidize glucose completely
3) Produces less ATP than either form of respiration
4) Uses pyruvate, or other organic molecule as terminal electron acceptor
5) Process may produce acids, alcohols, and gases
The pentose phosphate pathway is?
1) Necessary for production of NADPH and certain precursor metabolites
2) NADPH is a coenzyme needed for synthesis of nucleotides and fats
3) Required for the production of nucleotides, glucose (via photosynthesis), and some amino acids
Photosynthetic metabolism in a nutshell
1) Generate chemical energy (ATP) from absorbing light
– Utilizes an electron transport chain
– Yields O2
2) Calvin Cycle (most common pathway of carbon fixation)
– “Fixes” atmospheric CO2 to generate organic compounds
– Use ATP to provide energy to cycle
– Yields sugar (fructose)
Prokaryotes divided based on oxygen requirements
1) Obligate aerobes
2) Obligate anaerobes
3) Facultative anaerobes
4) Microaerophiles
5) Aerotolerant anaerobes
Obligate aerobes (2 main points)
– Absolute requirement for oxygen
– Need oxygen to produce energy
Obligate anaerobes (2 main points)
– No multiplication in presence of oxygen
– May cause death
Facultative anaerobes (2 main points)
– Grow better with oxygen
– Use fermentation in absence of oxygen
Microaerophiles (2 main points)
– Require oxygen in lower concentrations
– Higher concentration inhibitory
Aerotolerant anaerobes (2 main points)
– Indifferent to oxygen, grow with or without
– Do not use oxygen to produce energy
Optimum temperature -5°C to 15°C
– Found in Arctic and Antarctic regions
Psychrophile
Temperatures in 20°C to 30°C range
* Important in food spoilage
Psychrotroph
Temperatures in 25°C to 45°C range
- More common
- Disease causing
Mesophile
Temperatures in 45°C to 70°C range
* Common in hot springs
Thermophiles
Temperatures in 70°C to 110°C range
- Usually members of Archaea
- Found in hydrothermal vents
Hyperthermophiles
