chapter 8
DESCRIPTION
Chapter 8. Cellular Energy. Section 1. How Organisms Obtain Energy. Section 1: How Organisms Obtain Energy. All living organisms use energy to carry out all biological processes. Transformation of Energy Cellular processes require energy – the ability to do work. - PowerPoint PPT PresentationTRANSCRIPT
All living organisms use energy to carry out all biological processes.
Section 1: How Organisms Obtain Energy
KWhat I Know
WWhat I Want to Find Out
LWhat I Learned
How Organisms Obtain Energy
Transformation of Energy
• Cellular processes require energy – the ability to do work.
• Thermodynamics is the study of the flow and transformation of energy in the universe.
How Organisms Obtain Energy
Transformation of Energy
Laws of thermodynamics
• First law—the law of conservation of energy: energy can be converted from one form to another, but it cannot be created nor destroyed.
• Second law: energy cannot be converted without the loss of usable energy, that is, entropy—disorder or unusable energy--increases.
How Organisms Obtain Energy
Transformation of Energy
Autotrophs and Heterotrophs• Directly or indirectly, nearly all the energy for life comes from the
Sun.
• Autotrophs make their own food, either with energy from the sun or from inorganic substances.
• Heterotrophs ingest other organisms to obtain energy.
How Organisms Obtain Energy
Metabolism• All of the chemical reactions in a cell are referred to as the cell’s
metabolism.
• A series of chemical reactions in which the product of one is the substrate for the next is called a metabolic pathway.
• Catabolic pathways release energy by breaking down larger molecules.
• Anabolic pathways use energy to build larger molecules.
How Organisms Obtain Energy
Metabolism• Photosynthesis – anabolic pathway in which light energy from the
Sun is converted to chemical energy for use by the cell
• Cellular respiration – catabolic pathway in which organic molecules are broken down to release energy for use by the cell
How Organisms Obtain Energy
ATP: The Unit of Cellular Energy• In living things, chemical energy is stored in biological molecules.
• Adenosine triphosphate (ATP) is the most important biological molecule that provides chemical energy.
ATP Crash Course
https://www.youtube.com/watch?v=00jbG_cfGuQ
How Organisms Obtain Energy
ATP: The Unit of Cellular Energy
ATP structure
• Most abundant energy-carrier in cells
• Nucleotide made of an adenine base, a ribose sugar, and three phosphate groups
How Organisms Obtain Energy
ATP: The Unit of Cellular Energy
ATP function
• Releases energy when the bond between the second and third phosphate groups is broken.
• Transforms into a molecule called adenosine diphosphate (ADP) and a free phosphate group.
ATP
• When chlorophyll absorbs light, it is absorbing energy
• It stores it in the __________ of Adenosine Triphosphate (ATP)
bonds
ATP, continued.• Carbs are most commonly broken down to make ATP.
• Breakdown of glucose yields 36 ATP.
• ATP = Energy currency of the cell.
• Cells use ATP for functions such as building molecules & moving materials by Active Transport.
• ATP releases energy when phosphate group released.
• Becomes Adenosine DiPhosphate (ADP).– Can be converted back to ATP by adding phosphate.
Essential Questions• What are the two laws of thermodynamics?
• What is the difference between an anabolic pathway and a catabolic pathway?
• How does ATP work in a cell?
How Organisms Obtain Energy
Light energy is trapped and converted into chemical energy during photosynthesis.
Section 2: Photosynthesis
KWhat I Know
WWhat I Want to Find Out
LWhat I Learned
Crash Course: Photosynthesis
https://www.youtube.com/watch?v=sQK3Yr4Sc_k
Photosynthesis
Overview of Photosynthesis• Most autotrophs make organic compounds using photosynthesis.
• Photosynthesis is the process of converting light energy into chemical energy.
Photosynthesis
Overview of Photosynthesis• Photosynthesis occurs in two phases.
• In the light-dependent phase, light energy is converted into chemical energy.
• In the light-independent phase, chemical energy used to synthesize glucose.
Bill Nye: Photosynthesis
https://www.youtube.com/watch?v=pdgkuT12e14
Photosynthesis
Phase One: Light Reactions
• The absorption of light is the first step in photosynthesis.
• Once light energy is captured, it can be stored as ATP or NAPDH.
Photosynthesis
Phase One: Light Reactions
Chloroplasts• Are organelles that capture light energy
• Contain two main compartments:
• Thylakoids: flattened saclike membranes • Stacks of thylakoids are called grana.
• The fluid filled space outside the grana called the stroma
Photosynthesis
Phase One: Light Reactions
Pigments• Light-absorbing colored molecules called pigments are found in the
thylakoid membranes.
• Different pigments absorb specific wavelengths of light.
• Most common pigment in plants is chlorophyll.
• Plants also have accessory pigments.
Photosynthesis
Phase One: Light Reactions
Electron transport• The thylakoid membrane has a large surface area, providing space
for a large number of electron transporting molecules and two types of protein complexes called photosystems.
• Photosystems house the light-capturing pigments.
Photosynthesis
Phase One: Light Reactions
Electron transport• Light energy excites electrons in photosystem II.
• This light energy causes a water molecule to split – releasing an electron into the electron transport system, a hydrogen ion (H+ or proton) into the thylakoid space, and oxygen as a waste product.
Photosynthesis
Phase One: Light Reactions
Electron transport• The activated electrons move from photosystem II to an acceptor
molecule in the thylakoid membrane.
• The electron acceptor molecule transfers the electrons along a series of electron carriers to photosystem I.
Photosynthesis
Phase One: Light Reactions
Electron transport• In the presence of light, photosystem I transfers the electrons to a
protein.
• The protein transfers the electrons to the carrier molecule NADP+, forming the energy storage molecule NADPH.
Photosynthesis
Phase One: Light Reactions
Electron transport• ATP is produced in conjunction with the electron transport system
through chemiosmosis
• ATP is produced through the flow of electrons down a concentration gradient
• The breakdown of water provides the necessary protons for ATP synthesis
Photosynthesis
Phase Two: The Calvin Cycle (light independent reactions)• In the second phase of photosynthesis, called the Calvin cycle, energy
is stored in organic molecules such as glucose.
Photosynthesis
Phase Two: The Calvin Cycle• The first step of the Calvin cycle is called carbon fixation.
• CO2 molecules combine with 5-carbon molecules to form 3-phosphoglycerate (3-PGA)
Photosynthesis
Phase Two: The Calvin Cycle• In the second step, chemical energy stored in ATP and NADPH is
transferred to the 3-PGA to form glyceraldehyde 3-phospate (G3P).
Photosynthesis
Phase Two: The Calvin Cycle• In the third step, some G3P molecules leave the cycle to be used
for the production of glucose and other organic compounds.
Photosynthesis
Phase Two: The Calvin Cycle• In the fourth and final step, an enzyme called rubisco converts the
remaining G3P molecules into 5-carbon molecules called ribulose 1,5-bisphospates (RuBP).
• These molecules combine with new CO2 and continue the cycle.
2 Main steps of PS - Summary1. Light reactions—occurs only in the presence
of ___________– Occurs in the grana (thylakoids) of the
chloroplasts– Also known as Photolysis because light is used to
__________ _________ molecules into hydrogen and oxygen
light
split water
2 Main steps of PS - Summary2. Dark Reactions—can occur in light ____ darkness. Follows light reactions
– Occurs in the stroma of the chloroplasts– Also known as Carbon fixation because CO2 will get
“fixed up” with the hydrogens and energy from the light reaction
or
Light ReactionsTake place within the membrane of the
thylakoid.1. Chlorophyll absorbs energy from sunlight.
– Water is __________ _________– Oxygen is ______________
2. Oxygen leaves the plant and goes into the air
broken down
released
The Dark Reactions
Occur in stroma of chloroplasts.1. _________ is added to a cycle of
reactions to build larger molecules
2. A molecule of simple sugar is formed– _____________
CO2
glucose
Photosynthesis
Alternative Pathways
C4 plants
• The C4 pathway allows plants to maintain photosynthesis while reducing water loss.
• Significant structural modification in the arrangement of cells within the leaves – separate CO2 uptake from location of Calvin cycle
Photosynthesis
Alternative Pathways
CAM plants
• Crassulacean acid metabolism (CAM) is found in desert plants.
• Collect CO2 at night and store it in organic compounds
• During the day, release CO2 from organic compounds for the light-dependent cycle of photosynthesis
Bozeman Science: Photosynthesis
https://www.youtube.com/watch?v=g78utcLQrJ4
Essential Questions• What are the two phases of photosynthesis?
• What is the function of a chloroplast during the light reactions?
• How can electron transport be described and diagramed?
Photosynthesis
Living organisms obtain energy by breaking down organic molecules during cellular respiration.
Section 3: Cellular Respiration
KWhat I Know
WWhat I Want to Find Out
LWhat I Learned
Crash Course: Cellular Respiration
https://www.youtube.com/watch?v=00jbG_cfGuQ
Overview of Cellular Respiration• Organisms obtain energy in a process called cellular respiration.
• Respiration harvests electrons from organic molecules and uses the energy to make ATP.
• The equation for cellular respiration is the opposite of the equation for photosynthesis:
Cellular Respiration
Overview of Cellular Respiration • Cellular respiration occurs in two main parts: glycolysis and aerobic
respiration.
• Glycolysis is an anaerobic process, meaning it does not require oxygen.
• Aerobic respiration involves the Krebs cycle and electron transport.
• Aerobic processes require oxygen.
Cellular Respiration
Glycolysis
• Glucose is broken down in the cytoplasm through the process of glycolysis.
• Two molecules of ATP and two molecules of NADH are formed for each molecule of glucose that is broken down.
Cellular Respiration
Khan Academy: Glycolysis
https://www.youtube.com/watch?v=FE2jfTXAJHg
Krebs Cycle• Glycolysis has a net result of two ATP and two pyruvate.
• Most of the energy from the glucose is still contained in the pyruvate.
• In the presence of oxygen, pyruvate is transported into the mitochondrial matrix, where it is converted into carbon dioxide.
• The series of reactions in which pyruvate is broken down into carbon dioxide is the Krebs cycle, also know as the tricarboxylic acid (TCA) cycle
Cellular Respiration
Krebs Cycle
Steps of the Krebs cycle
• Prior to the Krebs cycle, pyruvate reacts with coenzyme A (CoA) to form acetyl CoA.
• Acetyl CoA moves into the mitochondrial matrix.
• Acetyl CoA combines with a 4-carbon compound to form citric acid.
Cellular Respiration
Krebs Cycle
Steps of the Krebs cycle
• Citric acid is broken down releasing two molecules of carbon dioxide and generating one ATP, three NADH, and one FADH2.
• Finally, acetyl CoA and citric acid are generated and the cycle continues.
Cellular Respiration
Steps of Kreb’s1. Pyruvate broken down 2. Coenzyme A3. Citric acid formed4. Citric acid broken down5. 5-carbon molecule broken down6. 4-carbon molecule rearranged
Up to 38 ATP molecules are made from the breakdown of 1 glucose molecule.
Khan Academy: Kreb Cycle
https://www.youtube.com/watch?v=juM2ROSLWfw
Electron Transport• In aerobic respiration, electron transport is the final step in the
breakdown of glucose.
• NADH and FADH2 from the Krebs cycle are used to convert ADP to ATP.
• Electron transport and chemiosmosis in aerobic respiration are similar to the processes of photosynthesis.
Cellular Respiration
Electron Transport
Prokaryotic cellular respiration
• Some prokaryotes undergo aerobic respiration.
• They do not have mitochondria, so they use the cellular membrane as the location of electron transport.
Cellular Respiration
Steps of ETC - Summary1. Electrons removed – High energy electrons from
NADH & FADH2.
2. Hydrogen ions transported – High energy electrons travel through the proteins in the ETC.
3. ATP Produced – ATP synthase adds phosphate groups to ADP to make ATP. For each pair of electrons that passes through the ETC, 3 ATPs are made.
4. Water formed – Oxygen enters cellular respiration process & picks up electrons & hydrogen ions to form water.
Khan Academy: ETC
https://www.youtube.com/watch?v=mfgCcFXUZRk
Anaerobic Respiration• When oxygen is unavailable, cells cannot follow glycolysis with the
aerobic respiration (Krebs cycle and electron transport).
• The anaerobic process that follows glycolysis is anaerobic respiration, or fermentation.
• Fermentation occurs in the cytoplasm of the cell, and produces NAD+ and ATP.
Cellular Respiration
Fermentation• Two types
– _______________ fermentation
– __________ ________ fermentation
Alcoholic
Lactic acid
Anaerobic Respiration
Lactic acid fermentation• Enzymes convert the pyruvate made during glycolysis into lactic
acid.
• Skeletal muscles produce lactic acid when the body cannot supply enough oxygen, such as during periods of strenuous exercise.
Cellular Respiration
Anaerobic Respiration
Alcohol fermentation • Occurs in yeast and some bacteria
• Converts pyruvate into ethyl alcohol and carbon dioxide
Cellular Respiration
PHOTOSYNTHESIS CELLULAR RESPIRATION
Organelle for process Chloroplast Mitochondrion
Reactants CO2 & H2O Sugars (C6H12O6) & O2
Electron Transport Chain Proteins within thylakoid membrane
Proteins within inner mitochondrial membrane
Cycle of chemical reactions Calvin cycle in stroma of chloroplasts builds sugar molecules
Krebs cycle in matrix of mitochondria breaks down carbon-based molecules
Equation 6CO2 + 6H2O C6H12O6 + 6O2 C6H12O6 + 6O2 6CO2 + 6H2O
Products Sugars (C6H12O6) & O2 CO2 & H2O
Photosynthesis & Cellular Respiration
Bozeman Science: Cellular Respiration
https://www.youtube.com/watch?v=Gh2P5CmCC0M