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.
• Metabolic activities alter molecules in a series of steps
• Enzymes (proteins) accelerate each step
• Enzymes regulated to maintain a balance of supply and demand
METABOLISM- ALL THE
CHEMICAL REACTIONS IN
ORGANISMS
Catabolic and Anabolic
Reactions
SWBAT:
Catabolic-give off energy by breaking
• Describe low down
of energy
through living
molecules
systems
Anabolic—use energy to build
• Compare chemical
processes of autotrophs
molecules
and heterotrophs
Energy released by catabolic
• Describe
role ofused
ATPtoindrive
metabolism
pathways
anabolic
• Describe how energy
released.
pathways
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
Energy
Ability to do work
Thermodynamics
Study 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.
nd
2
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/ATP
AMP
Adenosine
Monophosphate
ADP
Adenosine
Diphosphate
ATP
Adenosine
Triphosphate-
1
2
3
Energy to
form bonds
Small
Amount
More
Energy
Substantial
Energy
Energy
stored in
chemical
bonds
Minimal
Greater
Amount
Greatest
amount
Number of
phosphate
groups
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 oxygen
Basically Opposite of Cellular Respiration
Two Reactions of Photosynthesis
1. 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
Chloroplasts
Chloroplast: Organelle where photosynthesis
occurs
Thylakoids-Site of light dependent reactions
Grana: Stack of Thylakoids
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
NADPH
3.)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 Respiration
Mitochondria break down glucose to
produce energy (ATP)
Overview
•Every cell (plants and animals)
•Exergonic Reaction(produces energy)
•EquationC6H12O6 + ADP
6CO2 + 6H2O + ATP
Oxidation/Reduction Reactions
• Reduction
• Oxidation
–
–
–
–
–
adding O
removing H
loss of electrons
releases energy
exergonic
–
–
–
–
–
removing O
adding H
gain of electrons
stores energy
endergonic
oxidation
C6H12O6 + 6O2
 6CO2 + 6H2O + ATP
reduction
Cellular Respiration
Overview 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 organismssole 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 Carriers
Move electrons by shuffling H+ around
NAD+ → NADH
FAD+ → FADH2
like $$
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 Chain
Greatest 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
Carbon dioxide taken in
Energy of glucose released
Oxygen given off
Oxygen taken in
Carbon dioxide given off
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