Cellular Respiration the breaking down of food molecules

Cellular Respiration -the breaking down of food molecules in the presence of oxygen to release energy C 6 H 12 O 6 + O 2 CO 2 + H 2 O (glucose) + ATP (energy)

Metabolism • The set of chemical reactions in an • • organism’s cells that converts food into energy (ATP) “Burning calories” refers to how efficiently cells can perform cellular respiration More exercise = more energy required = more food required = faster metabolic rate

What is ATP? • Molecule that is used • • as an energy source in the cell Produced in mitochondria Food molecules are needed to make ATP

ATP Adenine P P P 3 Phosphate groups Ribose

ATP Adenine ENERGY stored in bonds P P P 3 Phosphate groups Ribose

ADP ATP P P ENERGY RELEASED PP

3 Steps of Cellular Respiration (each produces some ATP) 1) Glycolysis - splitting of glucose (2 ATP) (anaerobic - no O 2 needed) 2) Citric Acid (Kreb’s) cycle (2 ATP) (aerobic - O 2 needed) 3) Electron transport chain (32 -34 ATP) (aerobic) *steps 2 and 3 happen in mitochondria *step 1 happens in the cytoplasm outside the mitochondria

What happens without oxygen? • Citric acid cycle and electron transport • • chain (ETC) cannot occur Glycolysis is followed by fermentation There are two types of fermentation: alcoholic and lactic acid See diagram

O 2 Glucose Is split apart in Citric acid cycle and Electron transport chain Glycolysis No O 2

Alcoholic Fermentation • Happens in microorganisms (yeast and • • • bacteria) in the absence of oxygen (anaerobic) Alcohol and CO 2 are produced Does not produce ATP, but it does allow glycolysis to occur again and again Used in the beer and wine industry

Lactic Acid Fermentation • Happens in muscle tissue of humans and • • • other animals in the absence of oxygen (anaerobic) Lactic acid and CO 2 are produced Does not produce ATP, but it does allow glycolysis to occur again and again Produces burning feeling during exercise

When oxygen is present… • Kreb’s cycle (citric acid cycle) and electron transport chain occur • Both happen inside the mitochondria • 2 ATP come from the Kreb’s cycle • 32 -34 ATP come from the electron transport chain • Total of 36 -38 ATP from cellular respiration (includes 2 ATP from glycolysis) * ATP amounts shown are produced from ONE glucose molecule

Aerobic vs. Anaerobic Respiration • Energy produced quickly • No oxygen needed • Glycolysis and fermentation • Few ATP produced Aerobic Respiration • Energy produced more slowly • Oxygen needed • Citric acid cycle and ETC • More ATP are produced per molecule of glucose

What is Photosynthesis? The process of using sunlight to convert CO 2 and water into glucose and oxygen CO 2 + H 2 O C 6 H 12 O 6 + O 2 Reaction takes place in the chloroplast

Converting Solar Energy • Plants trap the sun’s • • energy using a green pigment called chlorophyll Chlorophyll is inside the chloroplast Solar energy is used to transform CO 2 into glucose

Factors that Affect Photosynthesis • Water availability • Light intensity (varies from species to species) • Temperature (extremes slow down photosynthesis - below 0 o. C and above 35 o. C)

Photosynthesis is divided into two processes:

Overview of Light Dependent Reactions • Require light to occur • Produce oxygen gas • Produce ATP

The Calvin Cycle Uses energy stored in ATP to produce glucose from CO 2. * Six CO 2 molecules from the atmosphere are needed to produce one glucose molecule