BIO 110 Exam 3 Study Guide

Redox Reactions

Reaction where electrons are transferred between two molecules

If a molecule has been reduced…

It gains electrons

If a molecule has been oxidized…

It loses electrons

Energy

Capacity to do work or capacity for change; usually changes form during chemical reactions

Chemical Reactions

Occurs when atoms collide with enough energy to combine or change their bonding partners

Metabolism

Sum total of all chemical reactions occuring in a biological system at a given time

Potential Energy

Stored energy (In chemical bonds, concentration gradient, or charge imbalance)

Kinetic Energy

Energy of movement

Anabolic Reactions

Complex molecules made from simple molecules - Energy required

Catabolic Reactions

Complex molecules broken down into simple molecules - Energy released

How are anabolic and catabolic reactions related

Energy released in catabolic reactions drive anabolic reactions

Laws of Thermodynamics

Apply to all matter and all the energy transformations in the universe

First Law of Thermodynamics

Energy in neither created nor destroyed

Second Law of Thermodynamics

When energy is converted from one form to another, some of that energy becomes unavailable to do work - no reaction is 100% efficient

Entropy

Measure of disorder in a system

Enthalpy (H)

Total energy

Free Energy (G)

Usable energy that can do work

What is change in energy measured in?

Calories or Joules

Change in G is negative (-)

Free energy is released

Change in G is positive (+)

Free energy is required

Exergonic Reactions

Release free energy (- Delta G)

Catabolism

Complexity decreases, generates disorder, complex molecules are converted to free energy and small molecules

Endergonic Reactions

Consume free energy (+Delta G)

Anabolism

Complexity/order increases, free energy and small molecules converted to complex molecules.

Chemical Equilibrium

Balance between forward and reverse reactions, Delta G = 0

Catalyst

Increases rate of chemical reaction, not altered by reaction, doesn't make a reaction occur that couldn't already occur

Enzyme

Biological catalysts that act as a framework in which reactions can take place, most are proteins

Activation Energy

Amount of energy required to start a reaction, can come from heating the system

Transition State

Reactive mode of the substrate after there has been sufficient input of energy to initiate the reaction

Transition State Intermediates

Unstable reactants with higher free energy

Substrates

Reactants; Molecules on which an enzyme exerts its catalytic action

Active Site

Place on an enzyme where substrate binds

Enzyme-Substrate Complex (ES)

Held together by hydrogen bonds, electrical attraction, or covalent bonds

What do enzymes do to the energy barrier during reactions?

Lower the energy barrier

What are the two things enzymes DON'T DO during reactions

Enzymes don't change final equilibrium and don't change that difference in free energy between reactants and products.

What are the three things enzymes can do in a reaction?

Orient substrates so they can react, induce strain by stretching substrate, and can temporarily add add chemical groups

Induced Fit

Enzyme changes shape when it binds substrate, altering shape of active site

Prosthetic Groups

Non-amino acid groups bound to enzymes

Inorganic Cofactors

Ions permanently bound to enzyme

Coenzymes

Small carbon-containing molecules; not permanently bound

What are the two ways enzyme activity is controlled?

Regulation of gene expression and regulation of enzyme itself

Enzyme Inhibitors

Molecules that bind to the enzyme and slow reaction rates

Naturally Occurring Enzyme Inhibitor

Regulates metabolism

Artificial Enzyme Inhibitors

Can be used to treat disease, kill pests, or study how enzymes work

Irreversible Inhibition

Inhibitor covalently bonds to side chains in active site and permanently inactivates the enzyme

Reversible Inhibition

Inhibitor bonds non-covalently to the active site, preventing substrate binding (Competitive, uncompetitive, and noncompetitive inhibitors)

Competitive Inhibitors

Compete with natural substrate for binding sites

Uncompetitive Inhibitors

Bind to enzyme-substrate complex, preventing release of products

Noncompetitive Inhibitors

Bind to enzyme at site other than the active site, changes enzyme shape

Allosteric Regulation

An effector binds an enzyme at a site different from the active site, changing the enzyme's shape

Allosteric Regulation Active Form

Can bind substrate

Allosteric Regulation Inactive Form

Cannnot bind substrate

Most allosteric enzymes are ________ with __________ structures

Proteins, Quaternary

What is the reaction rate of allosteric enzymes sensitive to?

Substrate concentration and low concentrations of inhibitors

What three things do metabolic pathways usually have

Starting material, intermediate products, and an end product

Commitment Step

First reaction, followed by other reactions in sequence

Feedback Inhibition

Final product acts as noncompetitive inhibitor of the first enzyme, shutting down the pathway

Do all enzymes work best on one specific pH?

No, each enzyme has a pH level it works best in

Aerobic Respiration

The process of using glucose and oxygen to produce ATP

Aerobic Respiration Formula

C6H12O6 + 6O2 → 6CO2 + 6H2O + 32 ATP

Photosynthesis Reaction

6CO2 + 6H2O —Light Energy→ C6H12O6 + 6O2

Electron Carrier Molecules

NADH, FADH2, NADPH

5 Principles of Metabolic Pathways

1. Complex transformations occur in a series of separate reaction; 2. Each reaction is catalyzed by a specific enzyme; 3. Many metabolic pathways are similar in all organisms; 4. In eukaryotes, metabolic pathways are compartmentalized in specific organelles; 5. Key enzymes can be inhibited or activated to alter the rate of the pathway

How do cells obtain energy?

From glucose in a series of metabolic pathways

What are the three catabolic processes that get energy from glucose

Glycolysis (anaerobic), Cellular Respiration (aerobic), and Fermentation (anaerobic)

In glucose metabolism, what is the reducing and oxidizing agents?

Glucose is the reducing agent and O2 is the oxidizing agent

What are the 5 Metabolic Pathways

Glycolysis, pyruvate oxidation, citric acid cycle, respiratory chain/ATP synthesis, and fermentation

What are the products of glycolysis?

2 ATP, 2 NADH, 2 pyruvate

What does glycolysis do?

Converts glucose into 2 molecules of pyruvate

Where does glycolysis take place?

In the cytosol

How many steps are in glycolysis?

10 steps: First 5 require ATP and the second 5 yield NADH and ATP

What are the products of pyruvate oxidation?

Acetate and CO2

Where does pyruvate oxidation take place?

In the mitochondrial matrix

What is the starting point of the citric acid cycle?

Acetyl CoA and oxidized e- carriers

What are the products of the citric acid cycle?

4CO2, 2ATP, 6NADH, and 2FADH2

Oxidative Phosphorylation

ATP is synthesized by reoxidation of electron carriers in the presence of O2

What are the two stages of oxidative phosphorylation

Electron transport and chemiosmosis

Electron Transport

Electrons from NADH and FADH2 pass through respiratory chain of membrane-associated carriers

Chemiosmosis

Protons flow back across the membrane through a channel protein, ATP synthase, which couples the diffusion with ATP synthesis

Where do NADH and FADH2 donate their electrons to?

The electron transport chain

Proton-Motive Force

Force generated across a membrane having two components - a chemical potential (difference in [proton]) plus an electric potential due to the electrostatic charge on the proton

How many ATP does the electron transport chain produce?

28 ATP

What are the two types fermentation?

Lactic acid and Alcoholic

What makes fermentation different from cellular respiration?

Its anaerobic (without O2)

Where does fermentation occur?

In the Cytoplasm

What things use fermentation?

Microorganisms and some vertebrate muscle cells

What are the products of alcohol fermentation?

2 Ethanol, 2CO2, and 2 ATP

Metabolic pathways don't operate in…

Isolation

Many metabolic pathways share…

Intermediate Molecules

Metabolic pathways are regulated by…

Enzyme Inhibitors

Gluconeogenesis

Glucose formed from citric acid cycle and glycolysis intermediates

Light

form of kinetic energy (waves and particles)

What does absorbed energy do?

pushes electron into an excited state by adding energy and moving it further from the nucleus; this makes it more reactive and unstable

What do pigments do with the sun’s light?

they absorb specific wavelengths in visible range

Examples of pigment molecules

chlorophyll a (alpha) and chlorophyll b (beta) absorb red and blue; carotenoids absorb blue-green and violet wavelengths

Absorbed wavelengths

useful in photosynthesis; photon adds energy to molecule, bringing it to an excited state

Reflected wavelengths

not useful in photosynthesis; the colors we see

Which wavelength is never absorbed?

green

Photosynthesis

energy from sunlight is captured and used to convert CO2 into more complex carbon compounds (redox process)

Importance of photosynthesis

it’s crucial for life as it produces O2 and helps plants convert sunlight into chemical energy