Chapter 8 Photosynthesis

Autotrophs vs. Heterotrophs Autotrophs are organisms that can make their own food ◦ Use light energy from the sun to produce ◦ Plants are an example Heterotrophs cannot use the sun’s energy directly ◦ Obtain energy from the foods they eat ◦ Animals and mushrooms are examples

Autotrophs vs. Heterotrophs

Energy ATP – Adenosine triphosphate – is the molecule cells use to store and release energy. Be able to draw it. Energy is released when the bond is broken between the last two phosphates. ADP – Adenosine diphosphate AMP – Adenosine monophosphate Adenosine

Energy

Energy Adding a phosphate group to ADP allows the organism to store energy ◦ ATP is like a fully charged battery ◦ ADP is like a partially charged battery

Energy Energy is used for: 1. Active transport: Na + is pumped out and K + into the cell 2. Motor proteins that move organelles 3. Synthesis of proteins, nucleic acids, lipids… 4. Produce light (firefly) 5. Cell reproduction and more

Energy Glucose is better for long term storage than ATP A single molecule of glucose stores 90 times the chemical energy of a molecule of ATP Most cells only have a small amount of ATP, only enough to last for a few seconds of activity

What is Photosynthesis? Photosynthesis is the process in which light, water, and carbon dioxide (CO 2 ) is made into sugar and oxygen (O 2 ) Carbon dioxide + water sugar + oxygen 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2

Photosynthesis Chlorophyll a and Chlorophyll b are pigments in the chloroplast that absorb light of the visible spectrum, except for green light. They reflect green, thus the leaf looks green.

Photosynthesis Photosynthesis takes place in the chloroplasts ◦ Chloroplasts have stacks of thylakoids (saclike photosynthetic membranes) ◦ Proteins in thylakoids organize chlorophyll and other pigments into photosystems, which are the light-collecting units

Light-dependent reactions Take place in the thylakoid membranes Convert light energy to ATP and NADPH Split H 2 O and release O 2 Electron transport chain connects the two photosystems to make an H+ gradient across the thylakoid membrane (ATP synthase uses this force to make ATP). Uses a proton (H + ) pump.

Light-dependent reactions

Calvin cycle reactions Take place in the stroma Use ATP and NADPH to convert CO 2 to sugar Return ADP, inorganic phosphate, and NADP + to the light reactions

Calvin cycle reactions

Photosynthesis

Factors affecting photosynthesis Water (required raw material) ◦ Plants in dry climates have a waxy coating to prevent water loss CO 2 concentration (required raw material) Temperature: enzymes function best between 0 o C and 35 o C Light intensity ◦ Plants can reach a maximum rate of photosynthesis with light intensity (varies between plant type)

Chapter 9 Cellular Respiration

Chemical Energy How much energy is in food? ◦ One molecule of glucose contains 3811 calories of heat energy ◦ A calorie is the amount of energy needed to raise the temperature of one gram of water one degree Celsius ◦ The Calorie (food labels) is actually 1000 calories

Chemical Energy The beginning of turning food into energy is glycolysis (produces small amount of energy) If oxygen is present 2 other pathways occur to produce more energy If oxygen is not present, 1 different pathway occurs

Energy Pathways Aerobic – requires oxygen ◦ Also called cellular respiration Anaerobic – does not need oxygen ◦ Fermentation – name for anaerobic pathway following glycolysis (if oxygen is not present). (The term fermentation includes glycolysis). Fermentation

What is Cellular Respiration? Cellular Respiration (video)(video) Cellular respiration - the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen. Glucose + oxygen  carbon dioxide + water + energy Glucose C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + ATP

What is Cellular Respiration? Carbon dioxide Water Oxygen Carbon dioxide

Cellular Respiration Steps of cellular respiration: 1. Glycolysis – one glucose is broken in half to make 2 pyruvic acids. Anaerobic. Occurs in cytoplasm. Glycolysis 2. Krebs cycle – pyruvic acid is broken down into CO 2 and energy. Aerobic. Occurs in mitochondrion. Also called citric acid cycle. Krebs cycle 3. Electron transport chain – using a series of proteins, the electrons from the Krebs Cycle and glycolysis to convert ADP to ATP. Electron transport chain

Glycolysis NADH passes energy from glucose to the electron transport chain

Energy Pathways Aerobic – requires oxygen ◦ Also called cellular respiration Anaerobic – does not need oxygen ◦ Fermentation – name for anaerobic pathway following glycolysis (if oxygen is not present). (The term fermentation includes glycolysis). Fermentation

Fermentation Two types of fermentation: Alcoholic fermentation: yeasts and some bacteria Pyruvic acid + NADH  alcohol + CO 2 + NAD + Lactic acid fermentation: most organisms including us and many bacteria Pyruvic acid + NADH  lactic acid + NAD + Both processes regenerate NAD +

Lactic Acid Fermentation

Kreb’s Cycle and ETC During the Kreb’s cycle pyruvic acid is broken down into carbon dioxide ◦ Occurs in the mitochondrion ◦ NADH and ATP is produced In the electron transport chain (ETC) high energy electrons (NADH, FADH 2 ) is converted into ATP ◦ Hydrogen ions are pumped across membrane ◦ ATP synthase – enzyme (protein) that makes ATP using H + gradient ATP synthase

Cellular Respiration 1 glucose results in the production of 36 ATP net ◦ 34 more ATP than anaerobic processes ◦ 38% of the total energy in glucose, the other 62% is “lost” through heat ◦ More efficient than an automobile (25%-30%) 70-75% is lost to heat

Energy Pathway Glycolysis No OxygenOxygen Anaerobic respirationAerobic respiration 36 ATP2 ATP, lactate or alcohol, and CO 2 Fermentation Cellular respiration

Cellular Respiration

Energy Pathway PhotosynthesisCellular Respiration Fermentation FunctionEnergy storageEnergy release LocationChloroplastsMitochondriaCytoplasm ReactantsCO 2 and H 2 OGlucose and O 2 Glucose & NAD ProductsGlucose and O 2 CO 2 and H 2 O & ATP Alcohol & CO 2 & ATP or Lactic acid & ATP Comparing photosynthesis, cellular respiration, & fermentation: