Cellular Energetics (Unit 3) Flashcards
What is a catalyst?
A chemical agent that speeds up reactions without being consumed
What is the structure of an enzyme
Tertiary structure
Can be charged made of polar amino acids (R group)
Endergonic
Endothermic and non spontaneous G>0
Exergonic
Exothermic and spontaneous G<0
What does induced fit mean?
Chemical groups of active site mold to catalyze substrate
How can an active site lower the activation energy?
- Orienting substrate properly
- Straining substrate bonds
- Favorable microenvironment
- Covalently bonding
What is denaturation?
Loss of conformational shape - typically not reversible
What is a prosthetic group?
A permanent non-protein enzyme helper
What is a cofactor?
A temporary non-protein enzyme helper
What is a coenzyme?
A organic non-protein enzyme helper
Describe competitive inhibition
Binding to active site and competing with substrate
Describe non competitive inhibition
Binding to the allosteric site, causing shape change, making active site less effective
What is metabolism?
All the chemical reactions in an organism
What is a catabolic pathway?
Releases energy by BREAKING DOWN complex molecules into simpler compounds
ex Cellular respiration
What is an anabolic pathway?
Consumes energy to BUILD molecules
ex. Dehydration synthesis of amino acids to build a protein
What is bioenergetics?
The stud of how energy flows through living organisms
What is spontaneous process?
Happens without energy input, increases the entropy of the universe
What are paired reactions?
One reaction feeding the energy requirements of another reaction
The entropy of an organism goes down, but the entropy of the universe goes up
Are cells at equilibrium? Why?
No. They are open systems with constant flow of energy and materials
How do cells manage energy resources?
Energy coupling ( use of exergonic reaction to drive an endergonic reaction) - mediated by ATP
How is energy from ATP released?
When the terminal phosphate bond is broken by hydrolysis
How does ATP drive endergonic reactions?
By phosphorylation, transferring a phosphate group to some other molecule (the phosphorylated intermediate)
How does a cell regulate metabolic pathways?
By switching on/off genes that ecode specific enzymes or regulation enzyme activity
What is allosteric regulation?
Occurs when a regulatory molecule binds to a protein at one end, affeting the function at another site (inhibits of stimulates the enzymes activity)
What is cooperactivity?
A form of allosteric regulation that amplifies enzyme activity
What is feedback inhibition?
The end product of a metabolic pathway shutting down the pathway
What happens in light dependant reactions
The chloroplasts trap solar energy and transform the energy to the reducing power of NADPH and the chemical energy of ATP
What happens in light independant reactions?
The energy of ATP and NADPH are used to reduce CO2 to synthesize glucose
What is chemiosmosis?
Energy store in a concentration gradient is used to generate ATP
What are autotrophs
Automatic feeder ( make their own food)
What are heterotrophs?
Organisms that obtain organic material from other organisms
What is a stack of thylakoids called?
Granum (plural = grana)
What is the space inside a thylakoid called?
Lumen
Where are chloroplasts found?
Mostly in the cells of the mesohpyll (interior leaf tissue)
Are guard cells photsynthetic?
Yes. They need glucose to power their cells to open/close
What is reduced in photosynthesis?
CO2 ——> C6H12O2 (gains e-)
What is oxidized in photosynthesis?
H2O2 ——-> 6O2
NADPH and ATP have major what power?
Reducing power so they give away e-
What are photosynthetic pigments?
They abosrb visible light
ex leaves are green because chlorophyll reflects green light
What happens when a pigment absorbs light?
it goes from a ground state to an excited (unstable) state
When the electron falls back to its ground state, photos are given off (afterglow/floresence)
Describe a photosystem
A photosystem consists of a reaction center complex (where chlorpohyll are found) surrounded by light harvesting complexes
What is/does a light harvesting complex do?
Pigment molecules bound to proteins
They transfer energy of photons to the reaction center
What does a primary electron acceptor do?
Accepts excited electrons and is reduced as a result
Where does the light reaction occur?
In the thylakoids
What happens in the light reaction?
- Splits H2O
- releases O2
- reduces the electron acceptor NADP+ to NADPH
- Generates ATP from ADP by phosphorylation
What does the proton pump do?
Pumps H+ into the thylakoid lumen, building up a concentration gradient
What does the concentration gradient do?
Flows out (passive transport) by moving through the transmembrane protein which spins and creates ATP
How is NADPH produced?
e- from photosystem 2 replaces e- photosystem 1 gave to carrier proteins, and the energy goes to producing NADPH
What is the reaction center chlorophyll of ps1?
P700
What is the reaction center chlorophyll of ps2?
P680
What is the calvin benson cycle?
The light independent reaction that occurs in the stroma of the chloroplasts
It reduces CO2 to Glucose
What happens in the first phase of the calvin benson cycle?
Carbon Fixation
Carbon enters as CO2 and leaves as G3P
What is the second phase of the calvin benson cycle?
Reduction
e- is gained by reducing a G3P (powered by oxidizing ATP)
What is the third phase of the calvin benson cycle?
Regeneration of CO2 acceptor (RUBP)
What is aerobic cellular respiration?
Requires a complete metabolic pathway by which electrons are transferred by high energy glucose to low energy O2
Energy is released a resynthesizes ATP from ADP and Pi
What is anaerobic cellular respiration?
Consumes thins other than O2
ex fermentation
What is fermentation?
The partial degradation of sugars without O2
It uses substrate level phosphorylation instead of ETC to generate ATP
What is oxidized and what is reduced in cellular respiration?
Glucose is oxidized, O2 is reduced
What is Nad+’s function?
Electron acceptor, but acts like an oxidizing agent during C.R
What happens in the first stage of cellular respiration?
Glycolysis - In cytosol
- Breaks glucose down into two molecules of pyruvate or pyruvic acid
What happens in the second stage of cellular respiration?
Citric Acid Cycle (kerbs cycle) - in Mitochondria
- Completes glucose breakdown
What happens in the third stage of cellular respiration?
Oxidative phosphorylation - in inner membrane of Mitochondria
- Most of ATP synthase (from e- transport chain and chemiosmosis)
Describe the krebs cycle
Completes the breakdown of glucose by oxidizing pyruvate.
generates 1 ATP, 3 NADH, 1 FADH2, and 2 CO2
Describe oxidative phosphorylation
Mitochondria transfer energy from chemical energy to ATP
Protons are pumped to inner membrane space and drive ATP synthase as they diffuse back to mitochondrial matrix
How do NADH and FADH2 relate to the electron transport chain in cellular respiration/
These electron carriers donate electrons to the ETC which powers ATP synthase via oxidative phosphorylation
What is the inner mitochondrial membrane called?
Cristae
What is the final electron acceptor in cellular respiration?
Oxygen
What is proton motive force?
H+ gradient (capacity to do work)
What is the energy flow in cellular respiration?
Glucose -> NADH -> ETC -> Proton Motive Force
What type of fermentation doesnt release CO2?
Lactic acid fermentation
What are obligate Anaerobes?
They carry out fermentation or anaerobic respiration and cannot survive in the presence of O2
What are facultative anaerobes?
Organisms that can survive by doing either type of cellular respiration
ex yeast
