Saturday, December 6, 2008

12/4/08 Blog

Hey girls! I hope everyone is having a great weekend! Because everyone has already done their 2nd quarter blog I'm posting the notes from last Thursday and if I wasn't supposed to post this blog-sorry! Don't forget that we have an essay on Monday as well as open book quizes for 9.1, 9.2, and 9.3.

The Process of Cellular Respiration

There are three types of cellular respiration: glycolysis, the Krebs cycle (Citric acid cycle), and the electron transport chain and oxidative phosphorylation.

9.2 Glycolysis harvests chemical energy by oxidizing chemical energy

Glycolysis is the breakdown of glucose to produce ATP. This is the first type of cellular respiration and is the only type that occurrs in all living orgainsms because it does not require oxygen. It also occurs in the cytosol of cells. Glycosis has 10 steps and 2 phases. The two phases are energy investment phase and energy payoff phase.

The phases:

During the energy investment phase the 6 carbon glucose molecule is phosphorylated. It then goes through different arrangements. It is later phosphorolated again- the molecule now has 2 phophate groups on opposite sides and has now used 2 ATP molecules. After this it is broken down into two diferent carbon sugars that are isomers of each other. During the energy payoff phase the sugar is oxidized by the transfer of electrons and H+ to NAD+ forming NADH. The sugar molecule then goes through a series of reactions and the ending product is a pyruvate molecule. ATP is produced by substrate-level phosphorylation and the transferring of phosphates in another reaction. Because the steps in the energy investment phase occur twice for each glucose molecule, 2 ATP are produced. Overall glycolysis has used 2 ATP, made 4 ATP molecules, and therefore has a net gain of 2 ATP molecules.

what do I need to know about glycolysis?

- it happens in the cytosol
- does not require oxygen
- is the breakdown of 1 glucose molecule into two pyruvate molecules
- net production of 2 ATP
- makes 2 NADH
-makes 4 ATP total
- bi products include carbon dioxide
- has two phases: energy investment phase and energy payoff phase

9.3 The citric acid cycle (the Krebs cycle) completes the energy-yeilding oxidation of organic molecules

If oxygen is present, the pyruvate molecules produced through glycolisis enter the mitochondrion. Like glygolysis, the steps involved in the Krebs cycle are each catalyzed by a different enzyme. There are 8 steps in this cycle.

Once pyruvate has entered the mitochondrion through active transport it is converted into acytyl coA. Step One: Acytol CoA adds its two-carbon groups to it producing citrate. Step two: citrate is converted to its isomer, isocitrate by the removal of one water molecule and the addition of another (it still contains 6 carbons). Step three: Citrate loses a CO2 molecule and the resulting compound is NADH. (5 carbons now remain) Step four: Another CO2 molecule is lost (4 carbons remain) and again reduces NAD+ to NADH. Step five: A molecule of ATP is formed through substrate-level phsophorylation). Step six: two hydrogens are trasnferred to FAD, forming FADH2. Step seven: water is added and it rearranges the bonds in the substrate. Step eight: the substrate is oxidized reducing NAD+ to NADH.

What do I need to know about the Krebs Cycle/ the Citric Acid Cycle?

- the net results are: 4 Co2, 2 ATP, 6 NADH, and an FADH2 molecule.
-requires oxygen
- is the 2nd type of cellular respiration
-occurs in the motochondrion
- between glycolysis and the Krebs cycle 4 molecules of ATP are formed
- the cycle happends twice (once for each pyruvate molecule)
- Acytol CoA is formed when pyruvate enters the mitochondrion

Here is a video that explains glycolysis:

Here is a video that explains the Krebs Cycle:


1) Glycolysis consists of how many phases?

A) 4

B) 2


D) 8

2) Which type of cellular respiration does not require oxygen?

A) glycolysis

B) Krebs Cycle

C) Oxidative Phosphorylation

Glycolysis produces a NET of how much ATP?

A) 34

B) 2

C) 4

D) It doesn't produce any ATP

Answers: 1) B, 2)A 3)B

I hope I got everything right! If I didn't please correct me in the comments section and I'll edit it. Good luck on the essay and quizzes!

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