Cellular Respiration

Pp 78-83

3.7 Cell respiration 3.7.1 Define cell respiration. 3.7.2 State that, in cell respiration, glucose in the

cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP.

3.7.3 Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP.

3.7.4 Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP.

Syllabus Definition

Cell respiration is the controlled release of energy from organic compounds in cells to form ATP

Metabolize/breakdown/ “slow oxidation”

Oxidation

Oxidation involves the loss of electrons from an element, whereas reduction involves the gain of electrons and that oxidation frequently involves gaining oxygen or losing hydrogen, whereas reduction frequently involves losing oxygen or gaining hydrogen.

 “Biology” definition of “oxidation”

cell respiration

Takes place in cytoplasm (glycolysis) and the mitochondria (Krebbs and Electron Tranport Chain)

Glucose is the major substrate for respiration

Adenosine triphosphates (ATP) is the product and the molecule which directly fuels the majority of biological reactions.

Why cell respiration?Cells require a constant source of energy (renewed daily) to perform various tasks e.g.

Metabolism, Synthesis, Active Transport, Locomotion, Cell Structure, Cell Communication, DNA/RNA Synthesis, tRNA Protein Synthesis

Types of Respiration

Occurs in the absence of Oxygen

(ii) Aerobic Respiration

Occurs in presence of Oxygen

Occurs in the cells’ cytoplasm Occurs in the cells’ mitochondria

Yields small amount of ATP (2 molecules) per molecule of glucose

Yields large amount of ATP (38 molecules) per molecule of glucose

Does not involve fermentationInvolves fermentation of pyruvate to lactate in muscles/CO2 & ethanol in plant & yeast

(i) Anaerobic Respiration

Comparison between Aerobic & Anaerobic Respiration -Animals

Adenosine triphosphate (ATP):ATP is the chemical

molecule which directly fuels the majority of biological reactions

About 1025 ATP molecules are hydrolysed to ADP and inorganic phosphate (Pi) daily

ADP is reduced back to ATP using the free energy from the oxidation of organic molecules

ATP Cycle

Anaerobic Cell Respiration anaerobic cell respiration occurs in

the absence of oxygen

during glycolysis glucose is broken breakdown in the cytoplasm

leading to the production of pyruvate,

production of small amount of energy (2 ATP molecules per molecule of glucose)

in muscles, pyruvate is converted into lactic acid during lactic acid fermentation

anaerobic respiration occurs in animals during intense muscular activity

in yeast & plant cells, pyruvate is

converted into alcohol (ethanol) & CO2

during alcoholic fermentation

no additional APT is produced during fermentation

“Three stages” of aerobic respirationStage 1: 2 ATP

Glycolysis (energy investment) 4 ATP is made, 2 is used –

Stage 2 (and 3): 38 ATP Krebs Cycle (oxidation of pyruvate)

Lots of energy carriers - Generation of CO2

Oxidative Phosphorylation Generation of most ATP

Outline the process of aerobic respiration

during glycolysis glucose is partially oxidized in the cytoplasm

small amount ATP produced during glycolysis

two pyruvate molecules are formed by glycolysis

pyruvate absorbed into mitochondrion

pyruvate is broken down in the mitochondrion in the presence of oxygen

to produce carbon dioxide & water

large amount of energy in form of ATP is produced per glucose molecule

WhereCell’s

cytoplasmWhy

To break glucose down into pyruvate, which feeds into the Krebs Cycle

To regenerate NAD, an electron carrier

Stage 1: Glycolysis

Krebs Cycle

Structure of a mitochondrion the electron micrograph

on the left shows the structure of a mitochondrion as seen under the electron microscope

draw a labelled diagram to show the structure of a mitochondrion

explain the relationship between the structure of the mitochondrion and its function

Structural adaptation of mitochondrion to its function

large inner surface area of cristae for respiratory complexes such as electron transport chains

matrix contains DNA and ribosomes for protein (enzyme) synthesis

it also contains Krebs cycle enzymes

double membrane(s) isolates metabolic processes from the rest of the cytoplasm

small intermembrane space between inner and outer membranes allows accumulation of protons for chemiosmosis

Aerobic respiration

Three stages of respiration

Summary