Packet 6 Cellular Energy ATP: cellular energy Why do cells need energy? Cells carry out three kinds...

Packet 6

Cellular Energy

ATP: cellular energy

Why do cells need energy?

• Cells carry out three kinds of energy-requiring work:– Chemical– Mechanical– Transport

Making ATP: Aerobic cellular respiration

Glycolysis (Stage 1) • Breaking down glucose

– “glyco – lysis” (splitting sugar)

– Occurs in the cytoplasm– A little ATP energy is harvested, – but it’s inefficient

• generate only 2 ATP for every 1 glucose

glucose pyruvate2x6C 3C

Overview10 reactions– convert

glucose (6C) to 2 pyruvate (3C)

– produces: 4 ATP & 2 NADH

– consumes:2 ATP

– net yield: 2 ATP & 2 NADH

Substrate-level phosphorylation

Substrate-level phosphorylation

Products of glycolysis move on to stage 2 or 3

intermembranespace inner

membrane

outermembrane

matrix

cristae

Mitochondria — Structure• Double membrane

– smooth outer membrane– highly folded inner membrane– intermembrane space– Matrix– DNA, ribosomes– enzymes

mitochondrialDNA

This happens twice for each glucose molecule that started glycolysis…why?

Stage 2: Pyruvate

grooming and the Kreb’s Cycle

Cellular respiration

Electron Transport Chain and Chemiosmosis: ATP payoff!

• Electron Transport Chain – series of proteins built into

inner mitochondrial membrane

Glycolysis Krebs cycle

8 NADH2 FADH2

Remember the Electron Carriers?

2 NADH

Time tobreak open

the piggybank!

Electron Transport Chain

What powers the proton (H+) pumps?…

Electronegativity!

Chemiosmosis and oxidative phosphorylation

oxidative phosphorylation

Cellular respiration

2 ATP 2 ATP 34 ATP+ +

~38 ATP

Summary of cellular respiration

• Where did the glucose come from?• Where did the O2 come from?

• Where did the CO2 come from?

• Where did the CO2 go?

• Where did the H2O come from?

• Where did the ATP come from?• What is recycled for use again?• Why do we breathe?

C6H12O6 6O2 6CO2 6H2O ~34-38 ATP+ + +

ETC backs up nothing to pull electrons down chain NADH & FADH2 can’t unload H

ATP production ceases cells run out of energy

Taking it beyond…• What is the final electron acceptor in

Electron Transport Chain?O2

So what happens if O2 unavailable?

Anaerobic respiration

Making ATP without oxygen

• All cells carry out glycolysis: prokaryotes and eukaryotes.• Eukaryotes and many prokaryotes also carry out oxidative phosphorylation

(remember this requires oxygen).

How can some bacteria carry out aerobic respiration if they don't have mitochondria?

FUN FACT: many bacteria have ETC’s in their cell membranes.

Reminders!A net of 2 ATP is generated in glycolysis.

NAD+ must be present available for this process.

New considerationsFor aerobic organisms this is not a problem, NAD+ is regenerated by the ETC.

Not all organisms can use oxygen, they are anaerobic

Anaerobic organisms use glycolysis only to make ATP

They regenerate , NAD+ through fermentation processes

Alcohol fermentation

Lactic acid fermentation

Review: Answer all of the following questions in your notebook.

• What are the products of pyruvate grooming for 1 molecule of glucose?

• What are the products of the citric acid cycle for 1 molecule of glucose?

• After glycolysis, pyruvate grooming, and the citric acid cycle, what are your net products?

• What is phosphorylation?• What is substrate-level phosphorylation?• What is the main goal for stages 1-3?

Review: Answer all of the following questions in your notebook

• What is the summary equation for cellular respiration?

• If oxidation is a loss of electrons (in the form of hydrogen atoms) and reduction is the gain of electrons (in the form of hydrogen atoms), – what is oxidized during cellular respiration? – what is reduced during cellular respiration?

• How does glucose get to your cells for cellular respiration?

• What is the point of cellular respiration?• What are the net molecular products of glycolysis?

Where does glucose come from for cellular respiration?

Photosynthesis!

Photosynthesis

Leaf structure

Mesophyll cells

Vascular tissueStomateGuard cells

Chloroplast structure Double membran

e

Stroma

ThylakoidGrana

Stage 1:

Light-dependent reactions

Stage 2:

Calvin cycle

Light energy is converted to chemical energy (as NADPH and ATP).

Glucose is made from CO2 and hydrogens carried by NADPH using ATP energy.

Calvin cycle

What factors might affect the rate of photosynthetic reactions?

SUMMARY