energy in cells. objectives: swbat: describe low of energy through living systems compare chemical...
TRANSCRIPT
Energy in Cells
Objectives:
SWBAT:
•Describe low of energy through living systems
•Compare chemical processes of autotrophs and heterotrophs
•Describe role of ATP in metabolism
•Describe how energy released.
METABOLISM- ALL THE CHEMICAL REACTIONS IN ORGANISMS
• Metabolic activities alter molecules in a series of steps
• Enzymes (proteins) accelerate each step• Enzymes regulated to maintain a balance of supply and demand
Catabolic and Anabolic Reactions
Catabolic-give off energy by breaking down molecules
Anabolic—use energy to build molecules
Energy released by catabolic pathways used to drive anabolic
pathways
SWBAT:
•Describe low of energy through living systems
•Compare chemical processes of autotrophs and heterotrophs
•Describe role of ATP in metabolism
•Describe how energy released.
Autotrophs vs Heterotrophs
Autotrophs-Make own food through anabolic reactions• Many autotrophs carry out photosynthesis
• Utilize cellular respiration
Heterotrophs-Can not make own food• Must eat other organisms to obtain energy
from food through catabolic reactions
• Utilize cellular respiration
EnergyAbility to do work
ThermodynamicsStudy of the flow and transformation
of energy in the universe.
1st Law of Thermodynamics
Law of conservation of energy
Energy can be converted but not created nor destroyed.
Example:Energy stored in food converted to chemical energy when we eat and
mechanical energy when you run.
2nd Law of Thermodynamics.
Energy cannot be converted without the loss of usable energy.
(Energy “lost” is converted to thermal energy)
Entropy
• Measure of disorder, or usable energy, in a closed system (not available for useful work)
• 2nd Law AKA “Entropy Increases”
• Food Chain –Useful energy available to next level decreases
Cell Energy
All living organisms must – produce from environment– store for future use– Use in a controlled manner
Where does Cell Energy Come From?
Sun → Autotrophs → Food → ATP
Types of Energy Cells Use
• Mechanical Work-moving cilia, contraction of muscle cells, movement of chromosomes
• Transport Work-Pumping substances
• Chemical Work-Synthesis of polymers, Bioluminescence
Adenosine Triphosphate (ATP)Multipurpose chemical energy
storage molecule
POWERS CELLULAR WORK
Objects compressed-store energy compressed object released- energy is
released.
Chemical bonds store energy, when bonds break energy is released.
Energy is stored in CHEMICAL BONDS
of molecules.
ATP (Adenosine Triphosphate)
•Adenine molecule
•Ribose sugar
•three phosphate groups
Forming and Breaking Down ATP
•Law of electrical charges•Bonding phosphate groups to adenosine required considerable energy.
AMP/ADP/ATPAMP
Adenosine Monophosphate
ADP
Adenosine Diphosphate
ATP
Adenosine Triphosphate-
Number of phosphate groups
1 2 3
Energy to form bonds
Small Amount
More
Energy
Substantial Energy
Energy stored in chemical bonds
Minimal Greater Amount
Greatest amount
3rd Phos + ADP ATP,
Phos so eager to get away, bond is broken a great amount of energy is release.
Energy available when ATP loses phos
Bonds Broken by Hydrolysis
ATP Cycle
•Doesn’t exist all the time as ATP. •Phosphate available--cell has an unlimited supply of energy.
Energy from Fuels• Digest large molecules into smaller ones
– break bonds & move electrons from one molecule to another• as electrons move they “carry energy” with them• that energy is stored in another bond,
released as heat or harvested to make ATP
Move electrons in Biology
“Glucose is like money in the bank; ATP is like money in your pocket”
We can write the overall reaction of this process as:
6H2O + 6CO2 ----------> C6H12O6+ 6O2
six molecules of water plus six molecules of carbon dioxide produce one molecule of
sugar plus six molecules of oxygenBasically Opposite of Cellular Respiration
Two Reactions of Photosynthesis1. Light Reaction ☼ – Light energy (sun)
into chemical energy.• Thylakoid Disk
• Produces ATP to power Light Independent Reaction.
• Oxygen Released
2. Light Independent Reaction/Dark Reaction (Calvin Cycle) – Uses chemical energy to “Fix” Carbon dioxide into sugar.
• Uses ATP and Electrons from Light Reaction
• Stroma
Mesophyll Cells
Specialized cells in the middle of the leaf that contain a lot of chloroplast
for photosynthesis
Chloroplast: Organelle where photosynthesis occursThylakoids-Site of light dependent reactionsGrana: Stack of Thylakoids
Chloroplasts
Stomata (stoma)Pores in plant’s cuticles through which water vapor and gases are exchanged between the plant and atmosphere (underside
of leaves)
Pigments: Molecules that absorb specific wavelengths of light (Plants: Chlorophyll-absorbs and transfers light energy)
**Chlorophyll forms a and b absorb most wavelengths except green. Because it doesn’t absorb it, it reflects it, hence green appearance.
Fall Colors
• Pigments other then chlorophyll
• Chlorophyll reduced revealing other pigments (carotenoids that are red, orange or yellow)
Light Dependent Reaction —“photo” of photosynthesis
1.)The light absorbed by chlorophyll causes a transfer of electrons and H+ from H20 molecules already present. This causes the H20 to split into molecular 0xygen (02) and a H+ ion (photolysis). 2.) The O2 is released (we breathe it) and the H+ bonds to NADP+ creating NADPH3.)ATP is formed through photophosphorylation. (ADP gets a phosphate group added to it creating ATP)4.) The NADPH and the ATP created here go on to fuel the reactions in the second part of photosynthesis - The Calvin Cycle
Photolysis: light causes water molecule split. Hydrogen to bind to an acceptor, subsequently releasing the oxygen.
Equation: H2O > 2H + O
Function:
• Release O2 gas to the atmosphere
• Replaces lost electrons
Calvin Cycle/Light Independent• “synthesis” of photosynthesis, making food, trapping
CO2.• Rubisco (enzyme) brings together CO2 and sugar,
carbon fixation– 3 CO2 (atmosphere) and 3, 5-carbon sugars (RuBP).
• PGA Formation-Six-carbon product is unstable and splits into 3-carbon products (PGA).
• ATP places a phosphate group on each PGA: NADPH donates a pair of electrons, yielding a high energy food, PGAL.
Calvin Cycle Completes
• Glucose Production-After several rounds 2 PGAL leave to form glucose
• Replenish RuBP (Ribose Biphosphate) Some PGAL reform 5-C Sugar-begin process again
Cellular RespirationMitochondria break down glucose to
produce energy (ATP)
Overview•Every cell (plants and animals)
•Exergonic Reaction(produces energy)
•Equation- C6H12O6 + ADP 6CO2 + 6H2O + ATP
Oxidation/Reduction Reactions• Oxidation
– adding O– removing H – loss of electrons– releases energy– exergonic
• Reduction– removing O– adding H – gain of electrons– stores energy– endergonic
C6H12O6 6O2 6CO2 6H2O ATP+ + +
oxidation
reduction
Cellular RespirationOverview three stages:
– Glycolysis• Cytoplasm• Glucose splits• Forms pyruvate (Intermediate-Acetyl CoA)
– Citric acid cycle (Kreb Cycle)• Converts Acetyl CoA into CO2
• Occurs in Mitochondrial Matrix
– Electron transport chain• ATP Synthesized
Glycolysis— “Sugar” splitting
•CYTOPLASM
• Yields little energy
•No oxygen required (anaerobic)
•Glucose (6 carbon sugar) → 2 Pyruvate and 2 ATP
•Prokaryotes and single celled organisms-sole source of energy.
History of Energy Harvest
• Energy transfer first evolved
• transfer energy from organic molecules to ATP
• still is starting point for ALL cellular respiration
Evolution• Prokaryotes
– first cells had no organelles• Anaerobic atmosphere
– life on Earth first evolved without free oxygen (O2) in atmosphere
– energy had to be captured from organic molecules in absence of O2
• Prokaryotes that evolved glycolysis are ancestors of all modern life– ALL cells still utilize glycolysis
Glycolysis Reactants and Products
REACTANTS•1 glucose•Enzymes•2 ATP are needed
• 2 Pyruvates • 4 ATP (net gain 2)• 2 NADH (go to
Electron Transport Chain (ETC))
Pyruvic acid forms Acetyl CoA
• Mitochondrion
• Pyruvic Acid combines with Coenzyme A to form acetyl CoA
Intermediate step Reactants and Products
REACTANTS•2 pyruvates (glycolysis)
PRODUCTS•2 Acetyl CoA (Go to Kreb Cycle)•2 CO2 (released as waste)•2 NADH (ETC)
Citric Acid Cycle (Kreb Cycle)
• Mitochondria
• Series of reactions
• Generates electrons for ETC
• Aerobic- Needs Oxygen
The Krebs cycle has five main steps. It starts with one molecule of Acetyl CoA (formed at end of glycolosis)
Step 1: Acetyl CoA, a two-carbon molecule, bonds with four-carbon oxaloacetic acid to form six-carbon citric acid.
Step 2:Citric acid releases a molecule of CO2 and a hydrogen atom, becoming a five-
carbon compound. The hydrogen atom bonds with NAD+, reducing it to NADH.
Step 3: The five-carbon compound releases another CO2 molecule and a hydrogen atom,
which again bonds with NAD+, producing NADH. This step is the same as step 2, except in this step one molecule of ATP is formed from an ADP and a phosphate.
Step 4: The new four-carbon compound releases another hydrogen atom. This time, the atom reduces a molecule of FAD to FADH2.
Step 5: The four-carbon molecule formed in step 4 releases a hydrogen atom, reforming oxaloacetic acid. hydrogen atom reduces another molecule of NAD+ to NADH.
Since one glucose molecule is converted into two pyruvic acid molecules by glycolysis, the Krebs cycle completes two turns for every molecule of glucose. This makes it produce 6 NADH molecules, 2 FADH, 2 ATP molecules, and 4 CO2 molecules.
Citric Acid cycle
REACTANTS•2 Acetyl CoA
PRODUCTS• 4 CO2 (waste)
• 6 NADH (ETC)
• 2 ATP
• 2 FADH2 (ETC)
Citric Acid Cycle/Kreb Cycle
Electron Transport Chain:• Mitochondria
• Series of reactions-electrons transported through chain
• NADH and FADH2 from Krebs Cycle carry electrons
• Electron route: food---> NADH ---> electron transport chain ---> oxygen
• Oxygen used
• Water released
Electron CarriersMove electrons by shuffling H+ around
NAD+ → NADH
FAD+ → FADH2like $$in the bank
reducing power!
Steps of Electron Transport Chain• Carrier molecules arrives, bumps the ETC’s first carrier, which
accepts the electrons, then passes them on along the chain (like a hot potato).
• Movement of electrons releases enough energy to power the movement of H+ ions from the inner compartment into the outer compartment (like heat of a hot potato dissipating as it is passed). The ions are being pumped against their concentration gradient.
• Hydrogen ions flow downhill through an enzyme called ATP synthase, like a water wheel spinning; as the ions pass, energy is used to transfer phosphate onto ADP to make ATP.
Electron Transport ChainGreatest amount of energy is made in this stage
(32-34 ATP per glucose)
Cellular Respiration
• Glycolysis: 2 ATP
• Krebs: 2 ATP
• Electron Transport: 32 for Eukaryotes, and 34 for prokaryotes.
• Total 36 for eukaryotes, and 38 for prokaryotes.
Anaerobic Respiration (fermentation)
• Cytoplasm
• Regenerates the cells supply of NAD+ (electron carriers)
• 2 Pyruvate and ONLY 2 ATP (glycolysis)
• Oxygen not being available as the final receptor in the ETC.
• Lactic Acid Fermentation and Alcohol Fermentation
Lactic Acid Fermentation
• Converts pyruvate to lactic acid.
• Transfers high energy electron and proteins from NADH.
• Strenuous exercise—muscle not supplied with enough oxygen.– LA builds up; muscles become sore, cramps and
fatigued– Panting helps provide extra O2; return to aerobic
conditions
Alcohol Fermentation
• Yeast and bacteria
• Pyruvate forms Ethyl Alcohol and CO2
• NADH donates electrons; NAD+ is generated.
• Baking---CO2 provides bubbles (dough rise)
• Alcohol—Consumable and ethanol
Comparison of Photosynthesis and Cellular Respiration
Photosynthesis Cellular Respiration
Food accumulated Food broken down
Energy from sun stored in glucose
Energy of glucose released
Carbon dioxide taken in Carbon dioxide given off
Oxygen given off Oxygen taken in
Produces glucose from PGAL Produces CO2 and H2O
Goes on only in light Goes on day and night
Only in presence of chlorophyll
All living cells
Alternative to Cellular Respiration: Fermentation