Ch. 9 - Cellular Respiration/Fermentation Study Guide A. Introduction 1. All living things need energy for metabolism. a. Plants produce glucose through photosynthesis; break down glucose during cellular respiration to release energy (ATP). b. Animals, Fungi, and non-photosynthetic Protists must consume food & break the food molecules/organic molecules (GLUCOSE) down to release energy (ATP). They too carry out the process of cellular respiration. NOTE: Photosynthetic protists such as Euglena also metabolize glucose by the process of cellular respiration. 2. When food molecules (a.k.a. organic molecules/carbs, proteins, lipids) are broken down energy is released & stored in ATP (adenosine triphosphate). 3. Production of ATP occurs in the MITOCHONDRIA of the eukaryotic cells. REMEMBER: MITOCHONDRIA ARE THE POWERHOUSE OF THE CELLS. 4. Animal, fungi, protists, and plant cells are all eukaryotic cells (have a nucleus) & all have mitochondria; therefore they ALL produce ATP. 5. How do they produce ATP? By the process of cellular respiration which occurs in all eukaryotic cells. B. Anatomy of the Mitochondria 1. Outer & inner membranes are made of lipids & proteins; has pores that allow substances to enter & leave the mitochondria.
2. Inner membrane has folds called cristae which increase surface area. 3. Fluid matrix refers to the fluid inside the mitochondria. 4. NOT SHOWN: Mitochondria also contain their own ribosomes & DNA; mitochondria are able to reproduce on their own. REMEMBER: mitochondria & chloroplasts are cousins to bacteria because they all have their own DNA, ribosomes & can reproduce on their own (binary fission). C. Cellular Respiration occurs only if oxygen is present. 1. Have you ever stopped to think about how the foods you consume on a daily basis are broken down to produce energy? Not only do you eat food on a regular basis, but you usually drink some type of water-based beverage with your meal & you breathe in oxygen too. 2. All cells must do work to stay alive and maintain homeostasis. The energy needed for cell work comes from the bonds of ATP (adenosine triphosphate). Cells get their ATP by breaking organic molecules (carbohydrates, lipids, & proteins), a process called cellular respiration. Although many organic molecules can be broken down, glucose, the main product of photosynthesis, is the primary fuel molecule for the cells of living organisms. 3. The energy stored in the foods organisms consume/eat is released during the process of cellular respiration. Every living organism, autotrophs and heterotroph, must do cell respiration. In fact, the metabolic pathways used in the process of cellular respiration are the same in virtually all eukaryotic organisms, and many prokaryotic organisms. Remember that organisms that do photosynthesis or chemosynthesis (make their own food molecules) are called autotrophs. Heterotrophs obtain their food molecules by eating other organisms. Animals, fungi, many protists and many bacteria are heterotrophs. Plants, some protists and some bacteria are autotrophs.
4. Eukaryotic organisms such as protists, fungi, plants, and animals are aerobic, meaning they need oxygen to survive. The oxygen that you & I breathe is needed during cellular respiration to break down the organic food molecules we eat and release energy that can be stored in ATP. 5. Reactants of cellular respiration: glucose, oxygen, water Products of cellular respiration: carbon dioxide, water, ATP (energy) 6. EQUATION FOR CELLULAR RESPIRATION glucose + 6 oxygen + 6 water ENZYMES 6 carbon dioxide + 12 water + 40 ATP/energy C6H12O6 + 6 O2 + 6 H2O ENZYMES 6 CO2 + 12 H2O + 40 ATP/energy NOTE: What do you notice about this equation; why does it seem familiar? The equation for cellular respiration is the exact opposite of the equation for photosynthesis. The products of photosynthesis become the reactants for cellular respiration; the products of cellular respiration (carbon dioxide & water) become the reactants for photosynthesis. 6 CO2 + 12 H2O sunlight/chlorophyll C6H12O6 + 6 O2 + 6 H2O 6 carbon dioxide + 12 water sunlight/chlorophyll glucose + 6 oxygen + 6 water D. How Does Cellular Respiration Occur? As with many metabolic processes, cell respiration has a number of stages. Glycolysis always occurs in the cytoplasm/cytosol of the cell & produces 2 ATP s (Four molecules of ATP are produced during glycolysis, but 2 molecules are consumed in activating the glucose.); glycolysis is an anaerobic process and does NOT need oxygen. All living organisms go through glycolysis; it is the most widespread metabolic process on earth. First prokaryotes on earth used glycolysis to produce energy because early atmosphere DID NOT contain oxygen. The first stage of glucose metabolism, or cell respiration, is a process called glycolysis, which splits a glucose molecule into two molecules of pyruvate (a.k.a. pyruvic acid), a 3-carbon molecule (these 6 carbons were originally in glucose).
If oxygen is available and the organism has the enzymes to do aerobic respiration, the 2 pyruvate molecules (a.k.a. pyruvic acid) will be broken down in the next stages of aerobic respiration: Kreb s Citric Acid Cycle and Electron Transport Chain. Krebs Citric Acid Cycle & Electron Transport Chain occurs in the mitochondria of the cell & produces 36 ATP s. Both the Krebs Citric Acid Cycle & Electron Transport Chain are aerobic processes and need oxygen in order to occur. The 2 pyruvate molecules leave the cytoplasm and enter the mitochondria. When they enter the mitochondria they are broken down into 6 carbon dioxide molecules during the Krebs Citric Acid Cycle. The Electron Transport Chain takes the hydrogen from glucose and use their energy to form ATP s. The hydrogens then combine with the oxygen you breathe to form water. NOTE: The 40 ATP s of energy released from a molecule of glucose represents 40% of its stored energy; the other 60% of the energy stored in glucose is released as heat & helps you maintain a constant body temperature. E. Fermentation Cellular Respiration Without Oxygen (Anaerobic Process) 1. Most living organisms must do aerobic cellular respiration to stay alive and provide their cells with 40 ATP s of energy. 2. When no oxygen is available (or is in short supply) for aerobic cellular respiration, or if the organism doesn t have the enzymes needed for cellular respiration, eukaryotic organisms, and some (bacteria), will break down glucose by the process of fermentation and produce 2 ATP s of energy. 3. Like cellular respiration, fermentation begins with the process of glycolysis occurring in the cytoplasm of the cell.
4. Two fermentation pathways in eukaryotes: a. Alcoholic Fermentation occurs in yeast cells (fungi) & some bacteria. Used in making bread, beer, & wine. glucose (6C) 2 pyruvate molecules (3C) 2 ethyl alcohol (2C) + 2CO2 + 2ATP s NOTE: The carbon dioxide gas makes bread dough rise & puts the holes in bread. Baking the dough causes the alcohol to evaporate. b. Lactic Acid Fermentation occurs in human/animal muscle cells. glucose (6C) 2 pyruvate molecules (3C) 2 lactic acid molecules(3c) + 2ATP s NOTE: Once the body s metabolism slows down, oxygen becomes available and lactic acid changes back to pyruvate (pyruvic acid), allowing continued aerobic metabolism (respiration) and energy (ATP) for the body.
F. How Are Photosynthesis & Cellular Respiration Related? PHOTOSYNTHESIS CELLULAR RESPIRATION OCCURS IN THESE ORGANISMS: ORGANELLES IN WHICH THESE PROCESSES OCCUR REACTANTS NEEDED: PLANTS & SOME PROTISTS (EUKARYOTES) SOME CYANOBACTERIA (PROKARYOTES) CHLOROPLASTS (PLANTS) CARBON DIOXIDE & WATER (INORGANIC MOLECULES) PROTISTS, FUNGI, PLANTS, ANIMALS (ALL EUKARYOTIC CELLS) MITOCHONDRIA GLUCOSE, OXYGEN, WATER PRODUCTS FORMED GLUCOSE, OXYGEN, WATER CARBON DIOXIDE, WATER, ATP (REMEMBER: ATP STORES THE ENERGY RELEASED FROM THE BREAKDOWN OF FOOD MOLECULES) OTHER REQUIREMENTS HOW PRODUCTS ARE USED BY LIVING THINGS ENERGY FROM SUNLIGHT, GREEN PIGMENT CHLOROPHYLL GLUCOSE-USED IN CELLULAR RESPIRATION BY ALL LIVING THINGS OXYGEN-RELEASED INTO AIR & USED TO BREAK DOWN GLUCOSE IN CELLULAR RESPIRATION WATER-RELEASED INTO AIR & BECOMES PART OF WATER CYCLE ENZYMES CARBON DIOXIDE-ANIMALS EXHALE IT INTO THE AIR & PLANTS USE IT IN PHOTOSYNTHESIS TO MAKE GLUCOSE WATER-USED TO REHYDRATE CELLS OR RELEASED INTO AIR/ENVIRONMENT ATP-STORES ENERGY RELEASED FROM BREAKING DOWN GLUCOSE & OTHER ORGANIC MOLECULES (LIPIDS, PROTEINS, OTHER CARBOHYDRATES)
Energy arrives from the sun and is captured by green photosynthetic plants, and stored in the chemical bonds of glucose. But non-photosynthetic organisms must obtain their energy by the breakdown of these energy rich storage molecules in order to release the energy for their use. Photosynthesis stores this energy in glucose, glycolysis and cellular respiration release energy. Within plant cells themselves these same processes happen in chloroplasts and mitochondria. Provides energy to autotrophs/ plants for PHOTOSYNTHESIS (in CHLOROPLASTS) CARBON DIOXIDE & WATER OXYGEN & GLUCOSE Taken in by heterotrophs (animals, fungi, protists)& plants (autotrophs) for CELLULAR RESPIRATION Glycolysis & Cellular Respiration (in CYTOPLASM) (in MITOCHONDRIA) 4040 HEAT ATP s of (60% of the energy ENERGY in glucose is released as heat energy) Used by cells for METABOLISM (The 40 ATPs represent 40% of the energy stored in glucose)
SUMMARY OF REACTIONS IN CELLULAR RESPIRATION & THE NUMBER OF ATPs THEY PRODUCE GLUCOSE (in cytoplasm of cell) GLYCOLYSIS (anaerobic) (in cytoplasm of cell) splits glucose into 4 ATP s produced (2 ATPs NET) 2 PYRUVATE MOLECULES (enter the fluid matrix of the mitochondria) KREBS CITRIC ACID CYCLE (aerobic) (in fluid matrix of mitochondria) 2 ATPs & 6CO 2 produced Hydrogen from glucose are passed to the ELECTRON TRANSPORT CHAIN (aerobic) (inner membrane of mitochondria) Hydrogen from glucose combine with oxygen we breathe to form water 34 ATPs & 12 H 2O produced A total of 40 ATPs of energy for cells to carry out metabolic activities.