Biol 213 Chapter 13

The breakdown and oxidation of food occurs in three steps

Catabolism

Food + O2 →

ATP + NADH +CO2 + H2O

Cellular respiration

The breakdown and utilization of sugars in a cell

Aerobic cellular respiration

the complete oxidation of food molecules, like glucose, to CO2 and H2O

• food + O2 → ATP + NADH + CO2 + H2O

Direct burning of sugar in nonliving system

• Large activation energy over some by the heat from a fire

• All free energy is released as heat; none is stored

Stepwise oxidation of sugar in cells

• Small activation energies overcome by enzymes that work at body temperature

• Much free energy is stored in activated carriers; the remainder is released as heat

The building of sugar =

Anabolism

Hoe do plants build sugars

Through photosynthesis

How do animals build sugar

Gluconeogenesis and glycogenesis

Photosynthesis

The building and eventual storage of Sugars in a cell

• the production of sugars, like glucose and starch, from light, CO2, and H2O

• Light dependent reactions → Calvin cycle → sugar formation

Electron carriers

• NADH

• FADH2

• NADPH

provide hydrogen

Glycolysis

Extraction of energy from splitting sugar

• conversion of glucose (6C) to two molecules of pyruvate (3C)

• 10 enzymatic steps (harvest energy in small steps)

• All steps occur in the Cytosol

ATP production in Glycolysis

• Requires an initial investment of two ATP

• Produce four ATP

• Net yield => two ATP

In glycolysis, no O2 is involved, but

Oxidation of an intermediate occurs

• (NAD+ → NADH)

• Yields two NADH per glucose

NAD+ vs NADH

NAD+ has one hydrogen while NADH has 2

Anaerobic conditions

• Fermentation in a vigorously active muscle cell → muscle and cancer cells

• Fermentation in yeast → yeast cells

Matrix of mitochondria in aerobic conditions

This space contains a highly concentrated mixture of hundreds of enzymes, including those required for the oxidation of pyruvate and fatty acids and for the citric acid cycle.

• citric acid cycle

• Pyruvate

• Dehydrogenase

Inner membrane of mitochondria in aerobic conditions

Folded into numerous cristae, the inner membrane contains the phosphorylation, including the Permeability barrier electron-transport chain and the ATP synthase that makes ATP. It also contains transport proteins that move selected molecules into and out of the matrix.

• Electron transport

• proteins that carry out oxidative

• ATP synthase

Outer membrane of mitochondria in aerobic conditions

Because it contains large, channel-forming proteins (called porins), the outer membrane is permeable to all molecules of 5000 daltons or less.

• porins

Intermembrane space of mitochondria during aerobic conditions

This space contains several enzymes that use the ATP passing out of the matrix to phosphorylate other Gradient nucleotides. It also contains proteins that

are released during apoptosis (discussed in Chapter 18).

• proton gradient

Pyruvate oxidation

Preparation for the citric acid cycle

• Pyruvate is transported into the mitochondria where it is oxidized to acetyl CoA and CO2 by a large, 3-enzyme complex: pyruvate dehydrogenase complex

Acetylene Cora to the citric acid cycle

• Complete oxidation of the acetyl

• group of acetyl CoA to CO2

• 8 enzymatic steps (harvest energy

• in small steps)

• In eukaryotic cells, all steps occur in

• the mitochondrion (matrix)

• High energy yield (per turn):

• 1 GTP

• 1 FADH2

• 3 NADH

• Does not use O2 directly, but

• requires O2 to regenerate NAD+

Glycolysis and the citric acid cycle provide the precursors needed for

cells to synthesize many important organic molecules. Together, they are often referred to as Central Metabolism