Transcript Completed notes
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.
K
What I Know
W
What I Want to Find Out
L
What I Learned
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. How Organisms Obtain Energy
ATP Crash Course https://www.youtube.com/watch?v= 00jbG_cfGuQ
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.
How Organisms Obtain Energy
ATP
• • When chlorophyll absorbs light, it is absorbing energy Triphosphate (ATP)
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.
ATP vs. ADP
ATP ADP Cycle
•
ATP Video
•
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
Section 2 Photosynthesis
Section 2:
Photosynthesis Light energy is trapped and converted into chemical energy during photosynthesis.
K
What I Know
W
What I Want to Find Out
L
What I Learned
Crash Course: Photosynthesis https://www.youtube.com/watch?v= sQK3Yr4Sc_k
•
Overview of Photosynthesis
Most autotrophs make organic compounds using photosynthesis. • Photosynthesis is the process of converting light energy into chemical energy.
Photosynthesis
THE FORMULA , continued.
• • •
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.
Photosynthesis
Bill Nye: Photosynthesis https://www.youtube.com/watch?v= pdgkuT12e14
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
Chloroplast structure
Phase One: Light Reactions
• • Pigments Light-absorbing colored molecules called pigments membranes.
are found in the thylakoid Different pigments absorb specific wavelengths of light.
• Most common pigment in plants is chlorophyll.
• Plants also have accessory pigments.
Photosynthesis
Video
•
Chlorophyll Borophyll
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. CO 2 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 CO 2 and continue the cycle.
Photosynthesis
2 Main steps of PS - Summary
1. Light reactions—occurs only in the presence – Occurs in the
grana
chloroplasts (thylakoids) of the – Also known as
Photolysis
because light is used to and oxygen
2 Main steps of PS - Summary
darkness. Follows light reactions – Occurs in the
stroma
of the chloroplasts – Also known as
Carbon fixation
because CO 2 will get “fixed up” with the hydrogens and energy from the light reaction
Light Reactions
Take place within the membrane of the thylakoid.
1. Chlorophyll absorbs energy from sunlight.
– – 2. Oxygen leaves the plant and goes into the air
The Dark Reactions
Occur in stroma of chloroplasts.
CO
1. _________ is added to a cycle of reactions to build larger molecules 2. A molecule of simple sugar is formed –
Video
•
Summary of Photosynthesis
Alternative Pathways
C 4 plants • The C 4 pathway allows plants to maintain photosynthesis while reducing water loss.
• Significant structural modification in the arrangement of cells within the leaves – separate CO 2 uptake from location of Calvin cycle Photosynthesis
Alternative Pathways
• CAM plants Crassulacean acid metabolism (CAM) is found in desert plants.
• Collect CO 2 at night and store it in organic compounds • During the day, release CO 2 cycle of photosynthesis from organic compounds for the light-dependent 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
Section 3 Cellular Respiration
Section 3:
Cellular Respiration Living organisms obtain energy by breaking down organic molecules during cellular respiration.
K
What I Know
W
What I Want to Find Out
L
What 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 Aerobic processes involves the Krebs cycle and electron transport.
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 FADH 2 .
• Finally, acetyl CoA and citric acid are generated and the cycle continues. Cellular Respiration
Steps of Kreb’s
1. Pyruvate broken down 2. Coenzyme A 3. Citric acid formed 4. Citric acid broken down 5. 5-carbon molecule broken down 6. 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
•
Kreb's cycle Video
• • •
Electron Transport
In aerobic respiration, electron transport is the final step in the breakdown of glucose.
NADH and FADH 2 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 - Summary
1. Electrons removed – High energy electrons from NADH & FADH 2 .
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
• Two types –
Fermentation
–
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
PHOTOSYNTHESIS CELLULAR RESPIRATION
Organelle for process Reactants Chloroplast CO 2 & H 2 O Mitochondrion Sugars (C 6 H 12 O 6 ) & O 2 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 Products 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 Sugars (C 6 H 12 O 6 ) & O 2 C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O CO 2 & H 2 O
Photosynthesis and Cellular Respiration
Cellular Respiration
Bozeman Science: Cellular Respiration https://www.youtube.com/watch?v= Gh2P5CmCC0M
•
Essential Questions
What are the stages of cellular respiration?
• What is the role of electron carriers in each stage of cellular respiration?
• What are the similarities between alcoholic fermentation and lactic acid fermentation?
Cellular Respiration