Cellular Energy: Photosynthesis and Cellular Respiration

Biochemical Processes and Energy Use Photosynthesis Cellular Respiration Radiant Energy Chemical Energy Heat Energy All living things must have energy. Energy Stored Energy Released Glucose Metabolized

Photosynthesis The key cellular process identified with energy production is photosynthesis. Occurs in the chloroplasts of plants. Photosynthesis – organisms (autotrophs) use the energy from light to convert inorganic substances (water and carbon dioxide) into high-energy carbohydrates (sugar) and oxygen, a waste product. + CO2 + H2O C6H12O6 + O2 Reactants Products

Leaves Carbon dioxide for photosynthesis enters holes in the bottom layer of the leaf, while oxygen leaves the same holes. These holes are called stomates or stoma. Stomates are surrounded by two guard cells that control their opening and closing. When it is hot, windy and/or dry, stomates close. When it is cooler or wet, stomates open.

How are materials transported in the plant? Vascular plants have the ability to transport material. Xylem- carries water Phloem carries sugar (C6H12O6) Ex- trees, ferns, tulip Non-vascular plants- Ex. moss

Factors affecting photosynthesis Factors that slow photosynthesis: Water shortage Some plants are adapted to dry conditions and have small leaves (pine trees) or a thick waxy, cuticle. Temperatures that are not ideal Enzymes function best between 0oC and 35oC. Low or high light intensity All plants have a maximum rate of photosynthesis, and without light, photosynthesis cannot occur.

Cellular Respiration Heterotrophs can’t make glucose so they must burn the stored energy made by plants. Cellular respiration is the process that releases energy by breaking down glucose and other food molecules for use by the cells. Cellular respiration includes: Aerobic reactions, which require oxygen and produce the most ATP molecules. Anaerobic reactions, which do not require oxygen and produce only a few ATP molecules. 7 7

Aerobic Respiration Requires Oxygen Takes place in the membrane-bound organelle called the mitochondria. Both plants and animals perform aerobic cellular respiration. C6H12O6 + O2 → CO2 + H2O + 36 ATP Reactants Products

Anaerobic Cellular Respiration If oxygen is not available at the end of glycolysis, then the cell will continue into an anaerobic process called fermentation. Formula – C6H12O6 CO2 + H20 + 2 ATP +alcohol or lactic acid Occurs in the cytoplasm of the simplest organisms like bacteria and yeast. There are two types of fermentation: Lactic acid fermentation (makes muscles sore) Alcoholic fermentation (yeast, a fungus in bread, uses alcoholic fermentation to flavor the bread and make it rise) 9 9

ATP Cells need energy to move, grow, reproduce, etc. ATP supplies this needed energy. Living things often store their energy in a molecule called adenosine triphosphate or ATP. ATP consists of: An adenine (adenosine) molecule A monosaccharide called ribose Three phosphate groups

adenine ribose

Anaerobic Respiration The Bottom Line Aerobic Respiration Requires oxygen. Happens primarily in the mitochondrion. For each glucose molecule 36-38 ATP molecules are made. Large and/or active organisms use aerobic respiration. Products are: Carbon dioxide and water Anaerobic Respiration Does not use oxygen. Happens only in the cytoplasm. For each glucose molecule 2 ATP molecules are made. Happens often in small organisms that do not require much energy. Products are either: Lactic acid, or Alcohol and carbon dioxide 12 12

Photosynthesis vs. Respiration Function: Capture energy Location: Chloroplasts Reactants: CO2 and H2O Products: C6H12O6 and O2 Organisms: All producers (autotrophs) Respiration Function: Release energy from organic molecules Location: Mitochondrion Reactants: C6H12O6 and O2 Products: CO2 and H2O Organisms: All 13 13