Cell Respiration Topic 2.8

The covalent bonds in a glucose, amino acid, or fatty acid store chemical energy. A small amount of energy is released whenever a covalent bond is broken. The ultimate goal of releasing energy in a controlled way is to trap the released energy in the form of ATP molecules

Cell Respiration Cell Respiration: the controlled release of energy from organic compounds in cells to form ATP ·Refers to a variety of biochemical pathways that can be used to metabolize glucose All of the pathways start with glycolysis

Use of ATP ATP is the primary source of energy for cells. Energy is stored in the covalent bonds between the phosphate groups When energy is needed ATP will be converted into ADP +Pi More energy can be obtained by creating AMP + 2Pi This process can be reversed by storing more energy in bonds creating ATP again.

Glycolysis is the first step in cellular respiration and the metabolic pathway common to all organisms on Earth. ·Occurs in the cytoplasm right outside the mitochondria ·Process of glucose (6 carbon molecule) being broken down into two smaller molecules called pyruvate (3 carbons each) ·Uses 2 ATP to catalyze the reaction but produces 4 ATP (net yield of 2 ATP)

After glycolysis, pyruvate can take two paths: After glycolysis, pyruvate can take two paths: anaerobic respiration or aerobic respiration Anaerobic respiration (aka fermentation) = no oxygen present ·Takes place in the cytoplasm of a cell Alcoholic Fermentation: Yeast convert pyruvate to ethanol (2C) and CO2 Lactic Acid Fermentation: Animals (humans) convert pyruvate to lactate(3C) (sometimes called lactic acid)

Aerobic respiration = oxygen is present ·Occurs in organisms that contain mitochondria ·Pyruvate moves into the mitochondria ·Pyruvate is broken down to produce CO2, water and 36 ATP molecules ·Most efficient pathway for energy

Photosynthesis Topic 2.9

Photosynthesis is the process of converting light energy from the sun into chemical energy Light from the sun is composed of a range of wavelengths Lower frequency wavelengths appear as red light Approx. 700nm in length Higher frequency wavelengths appear as blue/purple light Approx. 400 nm in length Midrange wavelength frequencies appear as green or yellow light

Photosynthesis takes place in chloroplasts ·The pigment inside chloroplasts that absorbs light energy is chlorophyll ·Chlorophyll absorbs red and blue wavelengths and reflects green and yellow wavelengths (which is why plants look green)

What is the energy from the light used for? The energy from the red and blue light is used to produce a small amount of ATP Create O2 by splitting water (process called photolysis) ATP and hydrogen (from the hydrolysis of water) are used to fix carbon dioxide molecules to an organic molecule in order to make glucose

How can we measure the rate of Photosynthesis? The rate of photosynthesis can be measured Directly - By the production of oxygen - By the uptake of carbon dioxide Indirectly - By an increase in biomass of a plant

Several environmental factors can affect the rate of photosynthesis: Temperature If temperatures get too high tiny pores in leaves called stomata will close to prevent loss of water This also prevents the uptake of carbon dioxide Results in a decrease in photosynthesis Temperatures lower than what a particular species of plant prefers can also result in a lower rate of photosynthesis

Optimal Temperature Rate of Photosynthesis Temperature

Light Intensity Light intensity tends to increase photosynthesis to a point Eventually the light intensity is so much that no more light can be absorbed by the amount of chlorophyll present and the rate of photosynthesis levels off

Carbon Dioxide Concentration Increasing carbon dioxide concentration will increase the rate of a photosynthesis to a point and then will level off the enzyme that binds or “fixes” CO2 is completely utilized (all of the active sites of particular enzyme in the chloroplast are full at any one point in time)