chatt.hdsb/~duncand/FOV1-000D8CF8/FOV1-000E9546/FOV1-000E954C/Krebs%20Cycle.pdf

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Cellular Respiration

The Mitochondria

The Mitochondria What characteristics do you notice about the mitochondria? What features does it have?

Mitochondrial Structure

Mitochondrion vs. Chloroplast What do they have in common? What appears different?

Both have their own DNA • Both are small like prokaryotes • Both make energy

Why are mitochondria important? • All cells require energy in the form of _______. • Mitochondria are the “powerhouses” that supply that energy by performing cellular respiration

What is Cellular Respiration? • Cellular Respiration is the process that releases energy by breaking down food molecules in the presence of oxygen. • all eukaryotic cells* • Takes energy from food (glucose) and turns it into a form cells can use (ATP)*.

BREATHING O2 CO2 Lungs CO2 Bloodstream O2 CELLULAR RESPIRATION

Cell Respiration Equation 6O2 + C6H12O2 6CO2 + 6H2O + Energy* Oxygen + Glucose  Carbon Dioxide + Water + Energy Does this equation look familiar? It should- It is the reverse of photosynthesis!

Parts of Cellular Respiration • Cell Resp. is broken into three parts:* • 1. Glycolysis • 2. Kreb’s Cycle • 3. Electron Transport Chain • Each stage uses chemical energy to make ATP.

Step 1 - Glycolysis • One molecule of glucose is broken in half, producing two 3-carbon molecules called pyruvic acid (pyruvate). • 2 ATP and 2 NADH are generated • Occurs in ______________. Cytoplasm

Cell Respiration Overview

Cell Resp. – Why is it important? • Cells require energy (ATP) to function • Glucose holds energy, but it must be “released” and converted to ATP for cells to use • Cellular respiration is the conversion of glucose to ATP

Glycolysis – Why is it important? • Glycolysis is the first step in converting glucose to ATP • Glucose is split up into two molecules of pyruvate • It takes 2 ATP to do this

Glycolysis • From glycolysis we get: • 2 molecules of ATP for instant use* • 2 molecules of NADH for ETC use • NADH holds high energy e-* • 2 molecules of pyruvate produce *

Advantages Fast Doesn’t require oxygen Disadvantages Cell’s NAD+ gets used up so quickly, glycolysis can’t go on for long Doesn’t make all that much ATP

After Glycolysis… Two Choices: Alcoholic Fermentation Fermentation No oxygen present Lactic Acid Fermentation Glycolysis (Respiration) Electron Transport Chain Oxygen present Kreb’s Cycle Fermentation = No ATP Respiration = Lots of ATP

Fermentation • When no oxygen is present, glycolysis is followed by fermentation rather than the Kreb’s cycle • Fermentation creates more electon carries (NAD+) so that glycolysis can make more ATP*

Fermentation • Fermentation converts NADH to NAD+ • Frees up NAD+ so glycolysis can continue and make more ATP • Fermentationis anaerobic* • Does not require oxygen*

Types of Fermentation • Alcoholic Fermentation(yeast* & bacteria) • Used to make cheese, bread, wine, buttermilk, etc.. Pyruvate + NADH  alcohol + CO2 + NAD+*

Types of Fermentation • Lactic Acid Fermentation(bacterial & muscle cells, • When muscles don’t get enough oxygen, lactic acid fermentation occurs • Build up of lactic acid makes muscles sore *pyruvate + NADH  lactic acid + NAD+

The Rest of Cell Respiration • If oxygen is present, the cell performs cellular respiration • After glycolysis, 90% of the energy from glucose is still unused • Final two steps in cell respiration extract that energy using oxygen • AEROBIC processes = require oxygen

Step 2 - The Kreb’s Cycle Matrix • Summary: • During the Kreb’s cycle, pyruvate is broken down into CO2 + energy (NADH)* • The Kreb’s cycle takes place in the matrix* of the mitochondria

Kreb’s Cycle • Pyruvic acid enters the mitochondrial matrix • One carbon molecule is lost as CO2 while NAD+  NADH • Remaining two carbon molecules combine with coenzyme A to form acetyl CoA

Kreb’s Cycle a.k.a Citric Acid Cycle

Kreb’s Cycle • Acetyl CoA is turned into CITRIC ACID. • Kreb’s Cycle a.k.a. Citric Acid Cycle • Citric acid is broken down and two CO2molecules are released • During this process, energy is released in the form of 8 NADH, 2 FADH2, and 2 ATP* • The remaining molecule, OXALOACETIC ACID(OAA), is used to restart the cycle.

Krebs Results • From all this we got 3 different forms of energy: • ATP – immediate cell usage • NADH • FADH2 Electron carriers that will bring high-energy electrons to ETC

Step 3 – Electron Transport Chain What did the ETC do in photo-synthesis?

Step 3 – Electron Transport Chain (ETC) • The electron transport chain uses high-energy electrons from the Kreb’s cycle to make ATP • Occurs in ____________________.* Cristae (inner membrane) Cristae (inner membrane)

Electron Transport Chain • Electrons from NADH and FADH2 are transported to the ETC* • At the end of the ETC sits oxygen*, which is very electronegative (it draws electrons near it) - this causes the electrons to travel down the ETC towards oxygen • Oxygen is the terminal electron acceptor • At the end of the chain, a protein combines the electrons with H+ and O- to make H2O*

Electron Transport Chain Meanwhile… • Every time 2 electrons move down the ETC, their energy pumps H+ ions into the inner membrane space, creating a concentration gradient* • The H+ ions then want to diffuse from the inner membrane space back to the matrix*

Electron Transport Chain • To cross the membrane, H+ moves through ATP synthase molecules making a gradient with the H+ * • Each time they do, it creates ATP • Chemiosmosis* • Each pair of electrons yields 3 ATP molecules

The Totals Glycolysis ? ATP Kreb’s Cycle & Electron Transport ?? ATP _______ Total ?? ATP

The Totals Glycolysis 2 ATP Kreb’s Cycle & Electron Transport ?? ATP _______ Total ?? ATP

chatt.hdsb/~duncand/FOV1-000D8CF8/FOV1-000E9546/FOV1-000E954C/Krebs%20Cycle.pdf