Transcript How Do Organisms Supply Themselves With Energy?

How Do Organisms
Supply Themselves
With Energy?
Key Questions
• How do organisms supply
themselves with energy?
• How do organisms extract energy
from glucose?
• How is the energy in glucose
used to make ATP?
How Do Organisms Supply
Themselves With Energy?
• All organisms need energy
• Ultimate source of energy on the Earth
is the sun
• Autotrophs make their own food;
– examples: plants, some bacteria
• Heterotrophs obtain chemical energy
from other organisms
– Examples?
Energy Currency
• Adenosine
Triphosphate
or ATP
• Cellular
respiration
produces
ATP
• Aerobic
versus
anaerobic
Cellular Respiration
Steps of Cellular Respiration
•
•
•
•
Step 1: glycolysis
Step 2: acetyl-CoA formation
Step 3: citric acid cycle
Step 4: electron transport and
oxidative phosphorylation
Cellular Respiration —
Chemical Equation
• C6H12O6
Glucose
+
6O2
Oxygen
• 6CO2 + 6H2O + ATP
Carbon Water Energy
Dioxide
What Is Oxidation?
• Oxidizing agent or electron acceptor
accepts an electron
• Reducing agent or electron donor donates
an electron
• Oxidation and reduction always go hand in
hand
• Examples of acceptors: O2, NAD+, FAD
Step 1: Glycolysis
Occurs in Cytoplasm
• Part 1: 6- carbon Glucose split into two 3-carbon
molecules and are phosphorylated; uses ATP
• Part 2: Phosphates and electrons are removed;
electrons added to NAD+ to make NADH; produces
2 ATP
Step 1: Glycolysis Cont.
• Part 3:
– More electrons and phosphates are removed
from the two 3-carbon molecules;
– phosphates are added to ADP to make ATP
Glycolysis Overview
• Breaks glucose into 2 molecules of pyruvate,
generating 2 molecules of ATP and 2 molecules
of NADH
 Aerobic or anaerobic? ANAEROBIC
 The pyruvate enters a cell’s ______.
MITOCHONDRIA
 When compounds are reduced, they ___
ACCEPT
electrons.
 When compounds are oxidized, they ___
DONATE
electrons.
 Which molecules/coenzymes from Glycolysis
accept electrons? NAD+
Step 2: Acetyl CoA
Occurs in ______
MITOCHONDRIA
• Oxygen needed for
this reaction; aerobic
• Pyruvate loses a
carbon and 2 oxygens
in the form of CO2
• Enzymes link
coenzyme A to the
acetate
 CoA synthesizes fatty
acids.
Step 3: Citric Acid Cycle
Overview
• High energy electrons
are captured in the
form of NADH and
FAD
• Occurs in the matrix
of the mitochondria
• With each turn of the
cycle, citrate loses a
total of 8 electrons to
electron acceptors
such as NAD+
Step 3: Citric Acid
Cycle
• 3 parts
– Part 1: 6-carbon
citrate and isocitrate
formation
– Part 2: conversion of
isocitrate into a 4carbon compound
– Part 3: production of
another molecule of
OAA, which starts the
cycle over again
Citric Acid Cycle
What If There Is No Oxygen?
• After glycolysis, if there is no oxygen,
fermentation will occur
• Cells must regenerate more NAD+ from
NADH
• Yeast — form ethanol (terminal reaction
produces CO2 )
• Animals — form lactic acid (ouch)
Biochemical
Pathway
Intersections
• Catabolism —
breakdown of complex
molecules such as
food; produces energy,
involves oxidation
• Anabolism —
synthesis of complex
molecules; uses
energy
Figure 6-7
How Do Other Food
Molecules Enter Metabolism?
• Fat, carbohydrates and proteins enter the
cellular respiration pathway at different
points
• The most
likely point is
at acetyl CoA
Electron Transport Chain
Step 4: Electron Transport &
Oxidative Phosphorylation
• The pathway of electrons from one carrier to
ELECTRON
CHAIN
another is called ____
____ TRANSPORT
_____;
• Each electron carrier passes its electrons to
the next carrier (bucket brigade)
• Most of the electrons to the electron transport
chain are received from what cycle? KREB’S
• A reduced carrier becomes oxidized when it
gives up its electrons (forms ATP from ADP)
• Oxygen accepts electrons
How Do Cells Harvest Energy?
• Proton gradient — flow of electrons
through the electron transport chain
creates this gradient (ATP is made from
this gradient)
• Chemiosmosis — harnessing of the
energy stored in the chemical gradient;
some machinery in the membrane must do
this process
Generating a Proton Gradient
• Mitochondria — inner and
outer membrane
• Intermembrane space —
space between 2
membranes
• Matrix — space within the
inner membrane; makes up
about 2/3 of the volume;
ETC is embedded in this
inner membrane
Pumping Protons
• pH & cytochromes assist w/ transport
of electrons.
• Gradient is produced when…..
ATP Synthase
• Proton complex
• Protons flow
through these
channels back into
the matrix
• Works like a turbine
• Uses energy to
make ATP
Key Concepts
• Cellular respiration converts the chemical
energy of food molecules into the chemical
energy of ATP
• Most cells can use glycolysis to obtain
energy
• ATP production from cellular respiration
depends on oxidative phosphorylation