Cellular Respiration and Photosynthesis PREAP REVIEW

Do you understand osmosis? Cell (compared to beaker)  hypertonic or hypotonic Beaker (compared to cell)  hypertonic or hypotonic Which way does the water flow?  in or out of cell

The Cell Membrane

Phospholipids Phosphate Lipids Phosphate head hydrophilic (water loving) Lipid tails hydrophobic (repels water) Arranged as a bilayer “attracted to water” Lipids “repelled by water” Why is a bilayer needed?

Arranged as a Phospholipid bilayer Serves as a cellular barrier / border sugar H2O salt polar hydrophilic heads nonpolar hydrophobic tails impermeable to polar molecules polar hydrophilic heads waste lipids

How do molecules pass through the cell membrane? Membrane becomes semipermeable via protein channels specific channels allow specific material across cell membrane inside cell H2O aa sugar salt outside cell NH3

Cell membrane defines cell Cell membrane separates living cell from its watery environment thin barrier = 8 nm thick Controls traffic in and out of the cell; “gatekeeper” allows some substances to cross more easily than others hydrophobic (nonpolar) vs. hydrophilic (polar)

Comparison of Fermentation to Cellular Respiration Lactic Acid Cellular Respiration Location glucose cytoplasm glycolysis (pyruvic acid) lactic acid + 2 ATP carbon dioxide + water + 36 ATP mitochondria

Which process – lactic acid fermentation or cellular respiration – produces the greatest amount of energy? Cellular respiration (36 ATP molecules) Which process – lactic acid fermentation or cellular respiration – can take place under anaerobic conditions (i.e., without oxygen)? Lactic acid fermentation Under what conditions do humans need to use both processes? During a time of intense exercise, humans revert from cellular respiration to lactic acid fermentation.

Comparison of Photosynthesis and Cellular Respiration Food synthesized Food broken down Energy from the sun stored as glucose Energy of glucose is released Carbon dioxide taken in Carbon dioxide given off Oxygen given off Oxygen taken in Produces sugars from PGAL Produces CO2 and H2O Requires light Does not require light Occurs only in the presence of chlorophyll Occurs in ALL living cells

Comparison of Photosynthesis and Cellular Respiration Photosynthesis Function: Energy capture Energy release Location: Chloroplasts Mitochondria Reactants: CO2 (carbon dioxide) and H2O C6H12O6 (glucose) and O2 Products: C6H12O6 and O2 CO2 and H2O Photosynthesis Equation: 6CO2 + 6H2O C6H12O6 + 6O2 Cellular Respiration Equation: C6H12O6 + 6O2 6CO2 + 6H2O energy energy

Reviewing Content In cells, the energy available in food is used to make an energy-rich compound called a. water. b. glucose. c. ATP. d. ADP. The first step in releasing the energy of glucose in the cell is known as a. alcoholic fermentation. b. glycolysis. c. the Krebs cycle. d. electron transport.

Reviewing Content The process that releases energy from food in the presence of oxygen is a. lactic acid fermentation. b. glycolysis. c. cellular respiration. d. photosynthesis. Which organisms perform cellular respiration? a. plants only c. animals only b. fungi and bacteria d. all living organisms

Reviewing Content The net gain of energy from glycolysis is a. 4 ATP. b. 2 ATP. c. 32 ATP. d. 36 ATP. Because fermentation takes place in the absence of oxygen, it is said to be a. aerobic. c. essential to O2 production. b. anaerobic. d. cyclic. The Krebs cycle takes place within the a. chloroplast. c. mitochondrion. b. nucleus. d. cytoplasm.

Reviewing Content The electron transport chain uses the high-energy electrons from the Krebs cycle to a. produce glucose. b. convert ADP to ATP. c. produce chlorophyll. d. change NAD+ to NADH. A total of 36 molecules of ATP are produced from 1 molecule of glucose as a result of a. alcoholic fermentation. b. lactic acid fermentation. c. glycolysis. d. cellular respiration.

Reviewing Content During heavy exercise, the buildup of lactic acid in muscle cells results in a. alcoholic fermentation. b. oxygen debt. c. the Calvin cycle. d. the Krebs cycle. When oxygen is your cells is depleted, ______ kicks in. a. lactic acid fermentation. b. aerobic cellular respiration.

Understanding Concepts How is glucose changed during glycolysis? What products are produced as a result of glycolysis? During glycolysis, 1 molecule of glucose is broken down into 2 molecules of pyruvic acid. The other products are ATP and high-energy electrons. Use a formula to write a chemical equation for cellular respiration. Label it with the names of the compounds. (light energy) 6C6H12O6 + 6O2  CO2 + 6H2O glucose + oxygen  carbon dioxide + water

Understanding Concepts How are fermentation and cellular respiration similar? What is the main difference between their starting compounds? Both are processes that break down glucose and release the energy stored in the molecule. Both start with the process of glycolysis, which produces pyruvic acid. Cellular respiration requires oxygen as a reactant. Fermentation is anaerobic.

Understanding Concepts When runners race for about 30 minutes, how do their bodies obtain energy? At the beginning of a race, runner’s energy comes from ATP that is present in their muscles and that is produced by lactic acid fermentation. When they continue to race, their bodies use cellular respiration to use stored carbohydrates to make ATP. If they are not in good shape and unused to running for 30 minutes, toward the end of their endurance, their bodies will switch back to lactic acid fermentation because their muscles will not be getting enough oxygen for cellular respiration to take place. If they continue running, they may “hit the wall” and collapse.

Understanding Concepts Complete the following concept map. Light Energy Photosynthesis CO2 and H2O 2 Glucose and O2 Cellular Respiration 1 ATP

Review Questions from the Orca Book

8.1 Section Assessment What factors affect the diffusion of water through a membrane by osmosis? The concentration on either side of the membrane (i.e., whether it is hypotonic, hypertonic, or isotonic) and the permeability of the membrane. How do animal cells and plant cells react differently in a hypotonic solution? In an animal cell, the extra water may cause the plasma membrane to burst. In a plant cell, the plasma membrane pushes against the cell wall, providing added support.

8.1 Section Assessment Compare and contrast active transport and facilitated diffusion. Both active transport and facilitated diffusion use carrier proteins. Facilitated diffusion does not require energy; active transport does. How do carrier proteins facilitate passive transport of molecules across a membrane? Carrier proteins move substances that cannot diffuse through the plasma membrane from an area of higher to lower concentration.

8.1 Section Assessment A paramecium expels water when it is in freshwater. What can you conclude about the concentration gradient in the paramecium’s environment? The environment is hypotonic and the concentration gradient is from outside to inside (water moves into the one-celled paramecium, and must be expelled or the paramecium could explode).

9.3 Section Assessment Compare the ATP yields of glycolysis, the Krebs cycle, and the electron transport chain. Glycolysis  2 ATP molecules, Krebs cycle  2 ATP molecules, electron transport chain  32 ATP molecules How do alcoholic fermentation and lactic acid fermentation differ? Both are anaerobic; but alcoholic fermentation produces alcohol, 2 ATP, and CO2, while lactic acid fermentation produces lactic acid and 2 ATP. Lactic acid fermentation occurs in animals, while alcoholic fermentation takes place in bacteria and in some yeast.

9.3 Section Assessment How is most of the ATP from aerobic respiration produced? Most is produced by reactions in the electron transport chain (32 of 36 ATP). Why is lactic acid fermentation important to the cell when oxygen is scarce? It supplies energy when oxygen is unavailable. How many ATP molecules are produced after the electrons go down the electron transport chain? 32 ATP

9.3 Section Assessment Compare the energy-producing processes in a jogger’s leg muscles with those of a sprinter’s leg muscles. Which is likely to build up more lactic acid? Explain. Aerobic respiration occurs in the muscles of both runners. The sprinter may build up more lactic acid because of an oxygen debt associated with a quick burst of energy.