Exam 3 - BIO140

Oxidation - Reduction (redox) reactions are

transfers electrons between molecules

Many biological processes conduct redox reactions using

electron carriers

NADH and FADH2 are

electron carriers and each carry 2 electrons

oxidized forms of NADH and FADH2

NAD+ and FAD

During cellular respiration, electrons carried by NADH and FADH2 go to the

electron transport chain

Aerobic cellular respiration

aerobic process of breaking down glucose to make lots of ATP and requires the presence of oxygen gas. It occurs in multiple stages.

Aerobic cellular respiration occurs in

inside mitochondria

Chemical equation for aerobic cellular respiration

C6H12O6+ 6O2 -> 6CO2 + 6H2O + 30-38 ATP

aerobic cellular respiration are _________ pathways

metabolic

Glycolysis

1st step of cellular respiration, breaks down glucose into 2 pyruvate molecules, the only step that occurs outside mitochondria (in the cell's cytoplasm) and does not require oxygen. It produces ATP and NADH.

Energy investment phase (in glycolysis)

requires an input of energy using 2 ATP molecules

Energy harvest phase (in glycolysis)

produces energy by forming 2 NADH and 4 ATP molecules

Net products from 1 single glucose molecule in glycolysis

2 pyruvate, 2 NADH, 2 ATP molecules

Glycolysis results in 2 pyruvate molecules which are then transported to the

mitochondrial matrix

Pyruvate Oxidation

2nd step of cellular respiration that converts each pyruvate into a molecule of Acetyl-CoA. It produces 2 acetyl-CoA, 2 NADH, and 2 CO2 molecules per 1 glucose.

Pyruvate Oxidation occurs in

mitochondrial matrix

Krebs Cycle/ Citric Acid Cycle

3rd stage of aerobic cellular respiration, oxidizes acetyl-CoA producing energy in the form of ATP, NADH, and FADH2.

Phases of Krebs cycle

1. Acetyl-CoA energy = 2 carbons of Acetyl-CoA enter and react with oxaloacetate producing citrate. CoA does not enter the krebs cycle, just the 2 carbons enter.

2. Citrate Oxidation = rearrangement and oxidation of citrate. Produces of 1 ATP, 2 NADH, 2 CO2 molecules.

3. Oxaloacetate regeneration = regeneration of oxaloacetate by oxidation, produces 1 NADH and 1 FADH2 molecule.

how many rounds of Krebs cycle occurs for every 1 glucose molecule

2

Electron Transport chain

4th step, consists of mitochondrial inner membrane proteins. Harness energy of electrons form NADH and FADH2 in a series of redox reactions. Uses energy from electrons to generate a H+ gradient by pumping H+ into the intermembrane space.

Final electron acceptor

the final molecule that accepts the ETC’s electrons is oxygen gas. When O2 serves as the final electron acceptor, it interacts with H+ to form water.

Chemiosmosis

diffusion of ions across a membrane down their concentration gradient.

ATP Synthase

enzyme that facilitates chemiosmosis and synthesizes ATP.

Remembering the stages of cellular respiration

Giant Pandas Killed Einstein

During aerobic cellular respiration, ATP is made through 2 different types of phosphorylation

substrate - level phosphorylation and oxidative phosphorylation.

Substrate - level phosphorylation

uses an enzyme and a substrate to directly transfer a phosphate group to ADP, creating ATP. Used to make a small amount of ATP during glycolysis and Krebs cycle.

Oxidative phosphorylation

Use energy from redox reactions in the electron transport chain to phosphorylate ADP. Builds H+ concentration gradient which is used to make a large amount of ATP. (Oxidative phosphorylation = ETC + Chemiosmosis)

Photophosphorylation

process by which light energy is used to produce ATP during the light dependent reactions of photosynthesis

Products for each stage of cellular respiration

Glycolysis: Glucose (start molecule) -> 2 ATP, 2 NADH, 2 Pyruvate

Pyruvate Oxidation: 2 Pyruvates (start molecule) -> 2 CO2, 2 NADH, 2 Acetyl-CoA

Krebs Cycle: 2 Acetyl-CoA -> 4 CO2, 2 ATP, 2 FADH2, 6 NADH,  Oxaloacetate

Oxidative Phosphorylation: NADH and FADH -> 26-34 ATP, H2O

What happens when there is no O2 in aerobic cellular respiration

The ETC gets backed up without O2 as the final electron acceptor. The amount of NADH increases while the amount of NAD+ decrease.

Anaerobic respiration

uses other molecules (instead of O2) as the final electron acceptor of ETC. The others are nitrate, sulfate, and CO2. It makes more ATP than fermentation but less ATP than aerobic cellular respiration.

Fermentation

process that uses the electrons from NADH to reduce pyruvate and regenerate NAD+

Regeneration of NAD+ allows

glycolysis to continue in the absence of oxygen

Lactic acid Fermentation

pyruvate is reduced by NADH to form lactic acid/lactate and NAD+, occurs in human muscles cells and in bacteria that gives yogurt its sour taste.

Alcohol fermentation

Pyruvate is reduced by NADH to form ethanol and NAD+. Produces beer from barley and wine from grapes.

Phosphofructokinase

A key enzyme in glycolysis that slows down when ATP binds to its regulatory site.

Pyruvate Processing

Converts pyruvate → acetyl CoA in the mitochondrial matrix (eukaryotes) or cytosol (prokaryotes), producing NADH & CO₂.

Pyruvate Dehydrogenase

The enzyme complex that catalyzes pyruvate processing; inhibited by ATP when energy is sufficient.

Photosynthesis

process that uses energy from sunlight to synthesize sugars (glucose). CO2, H2O and light energy are used to make glucose and O2.

Chloroplasts

green organelles that function as the site of photosynthesis, consists of 3 membranes

Autotrophs

photosynthetic organisms

Three possible outcomes for excited electrons in photosynthetic pigments

1. Electron drops back down to lower energy level; heat and fluorescence are emitted.

2. Energy in electron is transferred to nearby pigment

3. Electron is transferred to a new compound

Photosynthesis vs cellular respiration

both are ancient pathways that are highly connected, each process produces the reactants needed for the other. They are almost exactly the opposite of each other.

Mesophyll

interior leaf tissue consisting of mesophyll cells which has lots of chloroplasts

Stomata

tiny holes in the leaf that allow gas exchange of CO2, O2, H2O with the atmosphere

Chloroplasts power photosynthesis by

absorbing electromagnetic waves of light

Photons

particles of light with high kinetic energy that travel in waves with different wavelengths. The shorter the wavelength, the higher kinetic energy the photon has

Pigments

molecules that absorb wavelengths of visible light

the main photosynthetic pigment in chloroplasts is

Chlorophyll a

Accessory pigments

all other photosynthetic pigments that are not Chlorophyll a. Different pigments absorb different wavelengths of light. Some absorb and some reflect.

Types of Photosynthetic pigments

Chlorophyll a (green-blue), chlorophyll b (yellow-green), carotenoids (orange, red, yellow)

Photosystems

complexes of pigments, proteins and other molecules found in thylakoid membrane. Composed of several light- harvesting complexes surrounding a reaction center. Most plants have 2 photosystems involved with performing the light reactions of photosynthesis

Photosynthesis occurs in 2 stages

light reactions and calvin cycle

Light reactions

converts light and H2O into chemical energy and O2, occurs in the thylakoids within chloroplasts which contains photosystems.

Steps of light reactions:

Photosystem II, electron transport chain, Photosystem I, NADP+, Chemiosmosis

Photosystem II

Absorbs photons of light to energize electrons donated by a water molecule. Water molecules are split to provide electrons and react to form oxygen gas.

electron transport chain

Electrons move from photosystem 2 to photosystem 1 via an electron transport chain. This generates a hydrogen ion (H+) gradient.

Photosystem I

electrons are energized even more and continue through the Electron transport chain.

NADP+ serves as the

Final electron acceptor for calvin cycle and is reduced to form NADPH

Hydrogen ion (H+) gradient formed by the ETC is used to generate some ATP via

chemiosmosis.

Chloroplasts and Mitochondria use electron transport to

 synthesize ATP

3 types of ATP production

Substrate level phosphorylation, oxidative phosphorylation, photophosphorylation.

Calvin cycle

uses CO2 and chemical energy for the synthesis of glucose, 2nd stage using NADPH and ATP from light reactions to make organic molecule like glucose.

where does the calvin cycle occur

in the stroma of the chloroplast where it consumes CO2 gas from the atmosphere.

Phases of the Calvin cycle:

1. Carbon fixation: the enzyme rubisco adds CO2 to the 5-Carbon sugar RuBP. The first stable molecule produced is a 3-carbon molecule called PhosphoGlycerAldehyde (PGA)

2. G3P Synthesis: uses the PGA to synthesize G3P. Cell uses 2 G3P molecules to synthesize glucose.

3. RuBP regeneration: G3P is rearranged in a series of enzymatic reactions driven by ATP to regenerate RuBP.

Photorespiration

process causing plants to make CO2 rather than consume it. In hot environments, if stomata are open then plants are susceptible to dehydration.

Plants can prevent dehydration in hot environments by

closing their stomata

Cell division

process of a single cell dividing into 2 daughter cells

3 main types of cell division

Binary Fission, Mitosis, Meiosis

Binary fission

prokaryotic cell division, Bacterial chromosomes are replicated, Proteins filaments attach to replicated bacterial chromosomes, Filaments pull chromosomes apart, Other proteins divide cytoplasm.

Mitosis

eukaryotic cell division producing somatic cells (body cells), human somatic cells are diploid (2n) since they have 2 copies of every chromosome.

Meiosis

eukaryotic cell division producing gametes (sex cells), human gametes are haploid (n) since they have 1 copy of every chromosome

Basic steps in cellular replication

copying DNA, separating copies, dividing cytoplasm to create two complete cells.

2 types of reproduction

Asexual reproduction and sexual reproduction

Asexual reproduction

no sexual activity, only one parent involved, only one source of DNA = genetically identical offspring. (mitosis)

Sexual reproductions

sexual activity (two parents involved), two sources of DNA so genetically diverse offspring. (Meiosis)

Genome

the complete set of the cells DNA

genetic material

molecules that determine the inherited traits of an organism (usually DNA)

DNA associated with proteins called _______ to form units called nucleosomes

histones

Nucleosomes

units of 8 histone proteins at the core with DNA wrapped around it.

Chromatin

loosely packed/ coiled nucleosomes in non - dividing cells, dna molecule with histone proteins

Chromosomes

tightly packed, highly condensed, nucleosomes in a dividing cell.

Gene

region of DNA in chromosome, codes for specific RNA (specific protein)

Chromatid

each double stranded dna copy

Sister chromatids

two attached, double-stranded DNA copies of a replicated chromosome. When chromosomes are replicated, they consist of two genetically identical sister chromatids. When sister chromatids separate during mitosis, they become independent chromosomes.

Microtubule motor proteins

The dynein and kinesin motors that participate in moving chromosomes and the poles of the spindle apparatus.

Before a cell can divide

DNA must be replicated

DNA replication

produces an exact copy of all the DNA in a cell. Converts unreplicated chromosomes to replicated chromosomes with 2 identical sister chromatids.

centromere

where 2 chromatids join at

Cell is broken down into 2 major phases:

Interphase and Mitotic phase

Interphase

a non- dividing phase for cell growth, DNA replication and production of organelles/enzymes, includes 4 subphases: G0, G1, S and G2. Makes up the majority of the cell cycle.

Sub phases of interphase

G1 (growth), S (synthesis), G2 (growth) , G0

G1 (growth)

cell performs its normal functions, growing and producing organelles/enzymes/proteins

S (synthesis)

DNA synthesis/ replication producing replicated chromosomes with 2 sister chromatids

Centrosome

is a cytoplasmic protein complex that forms/organizes the mitotic spindle during mitosis.

Mitosis spindle

is a microtubule proteins of the cytoskeleton that coordinates division of chromosomes.

G2 (growth)

cell continues growth and produces new proteins required for M phase

G0

a non dividing phase where cells do not replicate their DNA nor prepare for division.

Mitotic Phase

a dividing phase that separates the genetic material while producing multiple cells. M phase = mitosis + cytokinesis. (takes short amount of time)

Mitosis

asexual process of dividing the nucleus and genetic material of a somatic (body) cell. Starts with one diploid cell and ends with 2 genetically identical diploid cells.