Cellular Respirationchapters 3.7 and 8.1

Cell Respiration Overview• A controlled release of energy

from organic compounds (will use glucose as our example) in cells to form ATP

• Enzymes are key to the metabolic pathways and cycles

• How can cells control the rate of enzyme pathways and cycles?

Need to respire

Respiration is required to generate heat energy as well as supply ATP for muscle contraction (movement) in animals.

Respiration is required to generate ATP for movement of sucrose in mass flow hypothesis in plants.

Respiration is required to generate ATP for mitosis for replication in bacteria.

Structure of ATPATP

P P P

Adenine 3 phosphate groups

ribose

P P

ADP

2 phosphate groups

ribose

Adenine

Practice

On your paper, draw a molecule of ATP. Label the parts of this molecule. Show how it becomes ADP.

Use of ATP

Cells need a supply of ATP molecules to act as an immediate energy source for many processes such as:

• active transport• maintaining resting potential in neurones• muscle contraction• cell division and growth• and most metabolic reactions

Mitochondria

Greatly increases the surface area for attachment of enzymes

For protein synthesis

The outer membrane is permeable to small molecules such as sugars, salts and nucleotides

The inner membrane is selectively permeable, which allows mitochondria to control the composition of the matrix

Codes for protein

Contains enzymes (proteins) ATP synthase

Structure RoleMatrix • Fluid filled. Contains enzymes required for the link

reaction and Krebs cycle.Cristae • Folded inner membrane.

• Electron transport system takes place here.• Cristae create a large surface area for ATP synthesis.

ATP synthase(stalked particles)

• Enzyme required for phosphorylation

• ADP + Pi ATPOuter membrane

• Controls the entry and exit of substances into and out of the mitochondria.• Pyruvate, O2, ATP move in; ATP and CO2 move out.

How is the mitochondrion adapted to carry out its

function? ( How is its structure related to its

function?)

Answer this question on your paper

Practice

Two types of respiration:

Aerobic-•in the presence of oxygen•happens in the mitochondria•much more efficient (yields more ATP)•starts with glycolysis and has 4 main stages

Anaerobic-•no oxygen needed•starts with glycolysis and has 2 main stages•2 types- lactic acid fermentation and alcoholic fermentation

Anaerobic respiration in mammals versus yeast

glucose pyruvate lactic acid

glucose pyruvate ethanol + CO2

Note: Some microorganisms can do both aerobic and anaerobic respiration and are called ‘facultative bacteria.’Lactic acid fermentation is reversible if O2 becomes present.Lactic acid must be sent to the liver to break down, thus if it stays too long in the muscles, it will cause them to be ‘sore.’

• glucose (C6) breaks down to 2 molecules of pyruvate (C3). (Note that compounds that end in ”-ate" can be called ”-ic acid". For example, lactate is lactic acid and malate is malic acid.)

• glycolysis occurs in the cytoplasm (cytosol)

• does not require oxygen

• Is the start to both aerobic and anaerobic respiration

• a total of 2 ATPs are gained (4 are produced and 2 are used to start the process for a total net of 2)

Glycolysis

Glycolysis

Pyruvate will either become a part of aerobic or anaerobic respiration depending on whether oxygen is present.

Aerobic Respiration recovers about 40% of the energy in glucose- more efficient than a modern car engine.

Glycolysis recovers only about 3% of the energy stored in glucose; nevertheless for a long period much of the history of life was written by organisms that could perform only glycolysis.

Many of the most successful organisms in existence are anaerobic and thus only achieve 3% efficiency.

Nonetheless it was only after the evolution of the Krebs Cycle and Electron Transport Chain that respiration could achieve a level of efficiency capable of sustaining larger, and more complex, multicellular organisms.