AP Biology Discussion Notes

Monday 12/01/2014

Happy December!

Looking Ahead…

• 13 class days left & 2 semester test days– 2 topics (cellular respiration & photosynthesis)

– 1 lab

– 2 quizzes

– 1 test

– X number of experiments

Goals for the Day1. Be able to write and describe the general

processes of cellular respiration and why organisms do this process

2. Be able to list which organisms do this process

3. Be able to describe and apply basic themes of energy transfer

Question of the Day

• What do you already know about cellular respiration?

Life Is Work• Living cells require energy from outside

sources• Some animals, such as the chimpanzee, obtain

energy by eating plants, and some animals feed on other organisms that eat plants

Figure 9.1

Figure 9.2

Lightenergy

ECOSYSTEM

Photosynthesisin chloroplasts

Cellular respirationin mitochondria

CO2 H2O O2

Organicmolecules

ATP powersmost cellular workATP

Heatenergy

• Energy flows into an ecosystem as sunlight and leaves as heat

• Photosynthesis generates O2 and organic molecules, which are used in cellular respiration

• Cells use chemical energy stored in organic molecules to regenerate ATP, which powers work

Concept 9.1: Catabolic pathways yield energy by oxidizing organic fuels

• Several processes are central to cellular respiration and related pathways

Catabolic Pathways and Production of ATP

• The breakdown of organic molecules is exergonic

• Aerobic respiration consumes organic molecules and O2 and yields ATP

Catabolic Pathways and Production of ATP

• Fermentation is a partial degradation of sugars that occurs without O2

• Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O2

• Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration

C6H12O6 + 6 O2 6 CO2 + 6 H2O + Energy

(ATP + heat)

Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose

How does cell respiration compare to Photosynthesis?

C6H12O6 + 6 O2 6 CO2 + 6 H2O + Energy (ATP + heat)

What organisms do these processes?

Photosynthesis Cell Resp.

•Prokaryotes?

•Eukaryotes?

• Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration

C6H12O6 + 6 O2 6 CO2 + 6 H2O + Energy

(ATP + heat)

Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose

Redox Reactions:AKA: Oxidation and Reduction

• The transfer of electrons during chemical reactions releases energy stored in organic molecules

• This released energy is ultimately used to synthesize ATP

Oxidation and Reduction

Figure 8.8b

Adenosine triphosphate (ATP)

Energy

Inorganicphosphate

Adenosine diphosphate (ADP)

(b) The hydrolysis of ATP

The Principle of Redox• Chemical reactions that transfer electrons between

reactants are called oxidation-reduction reactions, or redox reactions

• Oxidation - a substance loses electrons • (or is oxidized)

• Reduction - a substance gains electrons

– (or is reduced)

– the amount of positive charge is reduced

Figure 9.UN01

Figure 9.UN03

becomes oxidized

becomes reduced

Stepwise Energy Harvest via NAD+ and the Electron Transport Chain

• In cellular respiration, glucose and other organic molecules are broken down in a series of steps

• Electrons from organic compounds are usually first transferred to NAD+, a coenzyme

• Each NADH (the reduced form of NAD+) represents stored energy that is tapped to synthesize ATP

• NADH passes the electrons to the electron transport chain

• Unlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction

• O2 pulls electrons down the chain in an energy-yielding tumble

• The energy yielded is used to regenerate ATP

Figure 9.5

(a) Uncontrolled reaction (b) Cellular respiration

Explosiverelease of

heat and lightenergy

Controlledrelease ofenergy for

synthesis ofATP

Fre

e en

erg

y, G

Fre

e en

erg

y, G

H2 1/2 O22 H 1/2 O2

1/2 O2

H2O H2O

2 H+ 2 e

2 e

2 H+

ATP

ATP

ATP

Electro

n tran

spo

rt

chain

(from food via NADH)

The Stages of Cellular Respiration: A Preview

• Harvesting of energy from glucose has three stages

– Glycolysis (breaks down glucose into two molecules of pyruvate)

– The citric acid cycle (completes the breakdown of glucose)

– Oxidative phosphorylation (accounts for most of the ATP synthesis)

Figure 9.6-1

Electronscarried

via NADH

Glycolysis

Glucose Pyruvate

CYTOSOL MITOCHONDRION

ATP

Substrate-levelphosphorylation

Figure 9.6-2

Electronscarried

via NADH

Electrons carriedvia NADH and

FADH2

Citricacidcycle

Pyruvateoxidation

Acetyl CoA

Glycolysis

Glucose Pyruvate

CYTOSOL MITOCHONDRION

ATP ATP

Substrate-levelphosphorylation

Substrate-levelphosphorylation

Figure 9.6-3

Electronscarried

via NADH

Electrons carriedvia NADH and

FADH2

Citricacidcycle

Pyruvateoxidation

Acetyl CoA

Glycolysis

Glucose Pyruvate

Oxidativephosphorylation:electron transport

andchemiosmosis

CYTOSOL MITOCHONDRION

ATP ATP ATP

Substrate-levelphosphorylation

Substrate-levelphosphorylation

Oxidative phosphorylation

• Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration

• A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation

Figure 9.7

Substrate

Product

ADP

PATP

Enzyme Enzyme

• For each molecule of glucose degraded to CO2 and water by AEROBIC respiration, the cell makes up to 32 molecules of ATP

Reading/Video Assignment

Tasmanian Devil

Part I

Tasmanian Devil

Species of the day 12/01

Tasmanian Devil 

 Sarcophilus harrisii

What is the uncontrolled growth of this Tasmanian devil’s cells called?