Biology Exam 8

Cellular Respiration:

The stepwise transfer of energy from the bonds of glucose to the bonds of ATP. (How living things turn food into energy). 

What is cellular respiration carried out by?

Carried out by all living things:

* Animals
* Plants
* Fungi
* Bacteria 

What processes do plants carry out?

Plants do both cellular respiration and photosynthesis.

Where does the energy to form ATP come from?

The energy to form ATP comes from the **oxidation** of glucose. 

Why is glucose broken down in so many small chemical steps?

Cells break glucose down in a methodical, stepwise manner in order to release the energy in small, manageable amounts.

Why is releasing energy in small amounts good for the cell?

Since only a small amount of energy is released during each step, the cell doesn't overheat and the energy can be captured.

2nd reason as to why glucose broken down in so many small chemical steps?

Since its breakdown is organized into metabolic pathways, cells can regulate the pathways with feedback inhibition.

Oxidation:

Loss of electrons or H atoms by a molecule (Oxidation is loss OIL).

Reduction:

Gain of electrons or H atoms by a molecule (RIG reduction is gain).

Does the oxidized or the reduced form of a molecule have more energy?

The reduced forms of molecules have the electrons and have higher energy 

Give the equation for cellular respiration, indicating what is oxidized and reduced:

* Glucose is oxidized to become CO2
* Oxygen is reduced to form water

**Anaerobic:**

Does not require oxygen

**Aerobic:**

Requires oxygen 

What are the steps of cellular respiration if O2 is present?

If O2 is present glycolysis is followed by pyruvate, citric, and electron transport.

What are the steps of cellular respiration if no O2 is present?

 If no O2 is  present, then glycolysis is followed by fermentation. 

What stages of cellular respiration are anaerobic and aerobic?

Glycolysis- Anaerobic

Pyruvate, Citric Acid, And Electron Transport are Aerobic

__Glycolysis:__

The 6-C glucose is broken down into 2 3-C molecules= “glyco-lysis” 

Where does glycolysis/ Anaerobic reactions take place?

Anaerobic reactions go on in the cytoplasm

How does Glucose Get into the cell?

Facilitated diffusion b/c polar, hi to low, with a carrier protein.  

What are the stages of glycolysis?

1. Energy Investment
2. Cleavage
3. Energy Harvest

Glycolysis.

What happens during energy Investment?

2 ATPs are invested to ”energize”/phosphorylate the glucose. 

Glycolysis. 

What happens during cleavage?

The 6-C energized glucose is chopped into 2 3-C molecules of G3P 

Glycolysis. 

What happens during energy harvest?

* The G3P is oxidized, and an NAD+ is reduced to yield NADH 
* 2 ATP molecules are produced by substrate level phosphorylation

What is the most common process for ATP production?

Chemiosmosis

Substrate Level Phosphorylation (slp):

ATP is formed when an enzyme transfers a P from another molecule to ADP 

Where in cellular respiration does slp take place?

Only happens in the glycolysis and citric acid cycle.

How much ATPs are produced by slp?

* It only makes 4 out of the 34 ATPs 

Electron Carriers-

“Middlemen” holding electrons, hydrogens and energy between glucose and ATP.

What are the electron carriers in cellular respiration?

* NAD + (nucleotide)
* FAD (nucleotide)

NAD and FAD reduced forms:

* NADH
* FADH2

Glycolysis.

Which organic molecules go into the pathway?

Glucose.

Glycolysis. 

Which organic molecules and how many are produced per glucose?

2 Pyruvate molecules (3 carbon)

Glycolysis. 

How many total ATP are made?

How many net ATP are made?

4

2

Glycolysis. 

What type and how many carrier molecules are reduced per glucose?

2 NAD is reduced to NADH

What are the end products of glycolysis?

2 Pyruvate, 2 ATP, 2 NADH 

Where does pyruvate processing take place in the cell?

2 pyruvate moves into the mitochondrial matrix from the cytoplasm (where it was produced).

What happens during pyruvate processing?

* A carbon from each pyruvate is removed as CO2 (So 2 total per glucose)
* The  2-C fragment left is attached to a coenzyme, to yield acetyl CoA, which is now ready to enter the next stage (2 Acetyl CoA per glucose).
* 2 NADH are produced per glucose

Pyruvate Processing.

How many ATP are made?

0

**What’s produced at the end of pyruvate processing per glucose?** 

* 2 AcetylCoA’s
* 2 NADH
* 2 CO2

**Citric Acid Cycle (Krebs):**

Reactions in the mitochondrial matrix that break down and reform citric acid

What molecules enter this stage per glucose?

2 Acetyl CoA molecules go through per glucose.

What is vitamin C called?

ascorbic acid. 

What happens in the citric acid cycle?

1. Acetyl CoA is combined with a 4-C molecule (oxaloacetate) to make citric acid
2. The 2 carbons are pulled off as CO2’s (2 per Acetyl CoA).
3. Oxaloacetate is ready to bind to other acetyl CoA from another glucose.
4. Three more NAD+ are reduced to NADH
5. One FAD is reduced to FADH2 (continuing oxidation of glucose) 

CA.

What happens by the end of this cycle? What is special about it?

By the end of this cycle we have no more carbon.  

This is where most of the CO2’s of the original equation are produced 

CA.

How many ATP are made per glucose?

2 ATPs are produced through substrate level phosphorylation (1 per cycle)

What are the end products of the CA cycle per glucose?

NADH 6

FADH2 2

CO2 4 (organic)

CA cycle uniqueness:

Lipids and proteins can also be processed for energy here, enter as 2-C fragments. 

CA cycle uniqueness 2:

This cycle is also the place where any organic molecule can be made.

How are organic molecules made in CA cycle?

Monomers of these molecules enter glycolysis or the citric acid cycle at various points.

What happened to glucose by the end of this cycle?

At the end of this cycle, glucose has been completely dismantled: 

* Carbon, oxygen have been given off as CO2 (exhale) 
* The 12 H’s have been used to produce NADH or FADH2.

What happened to the temporary electron carriers by the end of the CA cycle?

By the end of the citric acid cycle, all the temporary electron carriers are in the reduced form= useless for further oxidation of glucose (need FAD+ and NAD to go to the previous stages of cellular respiration).

Where is the energy in the CA cycle?

* FADH2 and NADH are holding all of the energy that was in the original glucose molecule. 

What 4 carbon molecule is repeatedly joined to Acetyl CoA to create citric acid?

Oxaloacetate

Where does Electron Transport take place?

Electron Transport takes place on the inner membrane folds cristae of the mitochondrion. (Red in pic).

How many ATP’s has the cell made by now?

Glycolysis= NET profit 2 ATPs

Citric Acid Cycle= 2 ATPs, so 4 in total.

Both by substrate level phosphorylation.  

What is important about this stage?

Most of the ATP is produced in this stage when NADH’s and FADH2’s are oxidized to give off their hydrogens and electrons.  

PIC: ETC

Green are protein complexes. Pink is the matrix of mito, blue is the intermembrane compartment of mito. 

**Electron Transport Chain (ETC):**

Series of protein complexes embedded in a membrane that alternately accept and then donate electrons, releasing energy in small increments. 

What happens to the protein complexes are they donate or take in electrons?

The first protein complex with the electrons is reduced, it donates so it gets oxidized, then the second protein complex is reduced, etc.

Electron Transport Chain.

Main purpose:

Hydrogens and electrons are removed from NADH and FADH2, e- are passed down the electron transport chain (from green protein complex to green protein complex).

Electron Transport Chain.

What does the passing of electrons and hydrogens

do?

It oxidizes NADH, FADH2, regenerates NAD+ and FAD (b/c lost H+ and e-) to keep citric acid cycle, pyruvate processing, and glycolysis running. 

Complexes of ETC:

Complex I-IV- Made up of multiple proteins 

ETC.

what numbered protein complexes do something special?

Complexes I, III, and IV pump hydrogen (called proton pumps) ions (H+), out to the intermembrane space.

ETC.

What happens when the complexes pump hydrogen ions?

It creates a charge gradient, the power of this gradient results in ATP synthesis. 

ETC.

What are the other important components?

Q and Cyt C

ETC.

What is Q and Cyt C?

They are small, mobile electron carriers that ferry electrons between the complexes.

What does Q do?

Q carries electrons between complexes I, II, and III and ‘runs’ back to get some more electrons.

What does Cyt C do?

Cyt C carriers electrons between complexes III and IV.  

Electron Transport Chain. 

1st Step:

NADH’s enter in complex I to deliver its electrons and yield \~ 3 ATP’s each 

Electron Transport Chain. 

2nd Step:

FADH2’s enter at complex II it’s electrons have missed the first complex/ transfer so less energy will result so it yields- \~ 2 ATP’s each

Electron Transport Chain. 

3rd Step:

Oxygen accepts Hydrogens and electrons at complex IV, to become the water in the original equation. 

What is the role of oxygen in ETC?

It is The terminal hydrogen and electron acceptor which allows NAD+ and FAD to be regenerated.

Electron Transport Chain. 

4th Step:

ATP is made by chemiosmosis when hydrogen ions flow through ATP synthase.

What happens as hydrogen ions flow through ATP synthase?

Hydrogen’s energy as it flows from the intermembrane space through the ATP synthase into the mitochondrial matrix is used to make ATP. 

ATP Synthase:

Channel protein through which H+ ions flow, spans the inner membranes of chloroplasts and mitochondria. 

Chemiosmosis/Oxidative Phosphorylation:

Process where ATP is synthesized when H+ ions flow down a concentration gradient (high to low) (facilitated diffusion) through ATP synthase, releasing energy that drives the phosphorylation of ADP to ATP. 

ETC.

How many ATP are produced?

34 (4 out of the 38 were made previously)

ETC.

How many molecules of NAD are reduced to NADH?

0

ETC.

How many molecules of NADH are oxidized to NAD?

10

How many electron carriers are produced during pathways 1-3?

12 (10NADH, 2 FADH)

Why are the pyruvate processing and citric acid cycle considered aerobic?

The pyruvate processing and citric acid cycle is considered aerobic, because without O2, the cell would quickly run out of the NAD+ and FAD required.  

The transmembrane pump proteins of the electron transport chain are fueled by:

Electrons from glucose

It requires a lot of energy to make ATP from ADP because:

The  third negatively charged phosphate is repelled by the two phosphate groups in ADP

What does ATP synthase use for energy to fuel making ATP?

A gradient of protons.

ATP synthase is a turbine that generates mechanical energy to force phosphate groups onto ADP T OR F.

True

Our lungs take in oxygen and expel carbon dioxide, while our mitochondria take in carbon dioxide and expel oxygen T OR F.

False

**Fermentation:**

In absence of oxygen, follows glycolysis= glycolysis in never an end point. 

In fermentation, cells convert the pyruvate into: 

1. **Ethanol**
2. **Lactic Acid**

What is ethanol fermented by?

Fermentation by yeast

What is lactic acid fermented by?

Fermentation by animal cells, bacteria 

What food products are made by ethyl alcohol fermentation?

beverage alcohol, gasohol

What happens during ethanol fermentation?

1st step:

The pyruvate molecule from glycolysis loses one of its 3 carbons to become CO2. 2 CO2 made per glucose.

What happens during ethanol fermentation? 

2nd step:

The pyruvate molecule then turns into acetaldehyde.

What happens during ethanol fermentation? 

Between acetaldehyde and ethanol is a reduction (ethanol gets a hydrogen added on).

What happens during ethanol fermentation? 

The 2 NADH are oxidized which provides the hydrogen to ethanol and then turned into the 2 NAD. 

PIC: Ethanol fermentation

What can yeast also do?

Yeast can respire aerobically, have to make wine in airtight containers to force them into fermentation 

What is lactic acid fermentation carried out by?

**Lactic Acid carried out by human muscle cells during strenuous exercise**