Upload
amit-verma
View
215
Download
0
Embed Size (px)
Citation preview
7/30/2019 101pp Chapter 8
1/43
How Cells Release
Chemical Energy
Chapter 8
7/30/2019 101pp Chapter 8
2/43
Impacts, Iss ues:
When Mitochondria Spin Their Wheels
More than forty disorders related to defectivemitochondria are known (such as Friedreichs
ataxia); many of those afflicted die young
7/30/2019 101pp Chapter 8
3/43
8.1 Overview of Carbohydrate
Breakdown Pathways
ATP is the cells storage unit for energy
Photoautotrophs make ATP duringphotosynthesis and use it to synthesize glucose
and other carbohydrates
Most organisms, including photoautotrophs,
make ATP by breaking down glucose and other
organic compounds
7/30/2019 101pp Chapter 8
4/43
Main Pathways Of Respiration
Aerobic respiration
Aerobic metabolic pathways (using oxygen) are
used by most eukaryotic cells
Fermentation
Anaerobic metabolic pathways (occur in the
absence of oxygen) are used by prokaryotes andprotists in anaerobic habitats
7/30/2019 101pp Chapter 8
5/43
Comparison Of Main Pathways
Aerobic respiration and fermentation both begin
with glycolysis, which converts one molecule of
glucose into two molecules ofpyruvate
After glycolysis, the two pathways diverge
Fermentation is completed in the cytoplasm,
yielding 2 ATP per glucose molecule
Aerobic respiration is completed in mitochondria,
yielding 36 ATP per glucose molecule if all
processes there go to completion
7/30/2019 101pp Chapter 8
6/43
Respiration Pathways Power Actions
7/30/2019 101pp Chapter 8
7/43
Overview Of Aerobic Respiration
Three stages Glycolysis (carried out in cytoplasm; necessary to
set stage for mitochondrial processes that follow
Acetyl-CoA formation during Krebs cycle
Electron transfer phosphorylation (ATP formation)
C6H12O6 (glucose) + O2 (oxygen)
CO2 (carbon dioxide) + H2O (water)
Coenzymes NADH and FADH2 carry electrons
and hydrogen
7/30/2019 101pp Chapter 8
8/43
Aerobic Respiration Summary
7/30/2019 101pp Chapter 8
9/43
8.1 Key Concepts:
Energy From Carbohydrate Breakdown
Various degradative pathways convert the
chemical energy of glucose and other organiccompounds to the chemical energy of ATP
Aerobic respiration yields the most ATP from
each glucose molecule in eukaryotes; it is
completed inside the mitochondria
7/30/2019 101pp Chapter 8
10/43
8.2 Glycolysis
Glucose Breakdown Starts In Cytoplasm
Glycolysis starts and ends in the cytoplasm of all
prokaryotic and eukaryotic cells
An energy investment of ATP starts glycolysis
7/30/2019 101pp Chapter 8
11/43
Glycolysis Steps
Two ATP are used to split glucose and form 2
PGAL, each with one phosphate group
Enzymes convert 2 PGAL to 2 PGA, forming 2
NADH
Four ATP are formed by substrate-level
phosphorylation (gives net 2 ATP by process)
7/30/2019 101pp Chapter 8
12/43
Glycolysis Cytoplasm Only
7/30/2019 101pp Chapter 8
13/43
8.2 Key Concepts:
GlycolysisRespirations First Step
Glycolysis is the first stage of aerobic respiration
and of anaerobic routes such as fermentationpathways
Enzymes of glycolysis convert glucose to
pyruvate
7/30/2019 101pp Chapter 8
14/43
8.3 Respiration Second Stage
The second stage of aerobic respiration finishes
breakdown of glucose that began in glycolysis
Occurs in mitochondria
Includes two stages: acetyl CoA formation and
the Krebs cycle (each occurs twice in the
breakdown of one glucose molecule)
7/30/2019 101pp Chapter 8
15/43
Acetyl CoA Formation
In the inner compartment of the mitochondrion,
enzymes split pyruvate, forming acetyl CoA andCO2 (which diffuses out of the cell)
NADH is formed
7/30/2019 101pp Chapter 8
16/43
Krebs Cycle Summary
Krebs cycle
A sequence of enzyme-mediated reactions thatbreak down 1 acetyl CoA into 2 CO2
Oxaloacetate is used and regenerated
3 NADH and 1 FADH2 are formed
1 ATP is formed
All these products set stage for big payoff in ATP
storage in next process of sequence
7/30/2019 101pp Chapter 8
17/43
Inside A Mitochondrion
7/30/2019 101pp Chapter 8
18/43
Acetyl CoA Formation
And Krebs Cycle
7/30/2019 101pp Chapter 8
19/43
8.4 Aerobic Respirations
Big Energy Payoff
Many ATP are formed during the third and final
stage of aerobic respiration
Electron transfer phosphorylation
Occurs in mitochondria
Results in attachment of phosphate to ADP to
form ATP
Results in many times the ATP from glycolysis
7/30/2019 101pp Chapter 8
20/43
Electron Transfer Phosphorylation
Coenzymes NADH and FADH2 donate electronsand H+ to electron transfer chains
Active transport forms a H+ concentration
gradient in the outer mitochondrial compartment
H+ follows its gradient through ATP synthase,which attaches a phosphate to ADP
Finally, oxygen accepts electrons and combineswith H+, forming water
7/30/2019 101pp Chapter 8
21/43
Electron Transfer Phosphorylation
7/30/2019 101pp Chapter 8
22/43
Summary: The Energy Harvest
Typically, the breakdown of one glucose
molecule yields 36 ATP for all three stages:
Glycolysis: 2 ATP
Acetyl CoA formation and Krebs cycle: 2 ATP
Electron transfer phosphorylation: 32 ATP
7/30/2019 101pp Chapter 8
23/43
Aerobic Respiration Processes
7/30/2019 101pp Chapter 8
24/43
8.3-8.4 Key Concepts :
How Aerobic Respiration Ends
The final stages of aerobic respiration break
down pyruvate to CO2
Many coenzymes that become reduced deliver
electrons and hydrogen ions to electron transfer
chains; energy released by electrons flowing
through the chains is captured in ATP
Oxygen accepts electrons at ends of the chains
8 5 A bi
7/30/2019 101pp Chapter 8
25/43
8.5 Anaerobic
Other Energy-Releasing Pathways
Fermentation pathways break down
carbohydrates without using oxygen
The final steps in these pathways regenerate
NAD+ but do not produce ATP
7/30/2019 101pp Chapter 8
26/43
Other Fermentation Pathways
Glycolysis is the first stage of fermentation
Forms 2 pyruvate, 2 NADH, and 2 ATP
Pyruvate is converted to other molecules, but is
not fully broken down to CO2 and water
Regenerates NAD+but doesnt produce ATP
Provides enough energy for some single-celled
anaerobic species
7/30/2019 101pp Chapter 8
27/43
Two Pathways Of Fermentation
Alcoholic fermentation
Pyruvate is split into acetaldehyde and CO2
Acetaldehyde receives electrons and hydrogenfrom NADH, forming NAD+ and ethanol
Lactate fermentation
Pyruvate receives electrons and hydrogen fromNADH, forming NAD+ and lactate
7/30/2019 101pp Chapter 8
28/43
Two Pathways Of Fermentation
7/30/2019 101pp Chapter 8
29/43
Alcoholic Fermentation
7/30/2019 101pp Chapter 8
30/43
Fig. 8-10a, p. 133
7/30/2019 101pp Chapter 8
31/43
Fig. 8-10b, p. 133
Fermentation gives rise to doughs by CO2 release.
7/30/2019 101pp Chapter 8
32/43
Fig. 8-10c, p. 133
Yeast powers the fermentation of alcohol making and baking
7/30/2019 101pp Chapter 8
33/43
8.8 Muscles And Fermentation
Slow-twitch muscle fibers (red muscles) make
ATP by aerobic respiration
Have many mitochondria
Dominate in prolonged activity
Fast-twitch muscle fibers (white muscles) make
ATP by lactate fermentation
Have few mitochondria and no myoglobin
Sustain short bursts of activity
7/30/2019 101pp Chapter 8
34/43
Sprinters Use Lactate Fermentation
8 5 8 6 K C t
7/30/2019 101pp Chapter 8
35/43
8.5-8.6 Key Concepts :
How Anaerobic Pathways End
Fermentation pathways start with glycolysis
Substances other than oxygen accept electrons
at the end of the pathways
Compared with aerobic respiration, the net yield
of ATP from fermentation is very small
8 7 Alternative
7/30/2019 101pp Chapter 8
36/43
8.7 Alternative
Energy Sources In Body
Pathways that break down molecules other than
carbohydrates also keep organisms alive
In humans and other mammals, the entrance of
glucose and other organic compounds into an
energy-releasing pathway depends on the kinds
and proportions of carbohydrates, fats andproteins in the diet
So What Happens To Glucose At
7/30/2019 101pp Chapter 8
37/43
So What Happens To Glucose At
Mealtime And Between Meals
Its a constant balancing act
When blood glucose concentration rises, the
pancreas increases insulin secretion Cells take up glucose faster, more ATP is formed,
glycogen and fatty-acid production increases
When blood glucose concentration falls, thepancreas increases glucagon secretion
Stored glycogen is converted to glucose
7/30/2019 101pp Chapter 8
38/43
Energy From Fats
About 78% of an adults energy reserves is
stored in fat (mostly triglycerides)
Enzymes cleave fats into glycerol and fatty acids
Glycerol products enter glycolysis
Fatty acid products enter the Krebs cycle
Compared to carbohydrates, fatty acid
breakdown yields more ATP per carbon atom
7/30/2019 101pp Chapter 8
39/43
Energy From Proteins
Enzymes split dietary proteins into amino acid
subunits, which enter the bloodstream Used to build proteins or other molecules
Excess amino acids are broken down into
ammonia (NH3) and various products that canenter the Krebs cycle
Alternative Energy Sources In Human
7/30/2019 101pp Chapter 8
40/43
Alternative Energy Sources In Human
Body Proteins And Fats
8 7 Key Concepts:
7/30/2019 101pp Chapter 8
41/43
8.7 Key Concepts:
Other Metabolic Pathways
Molecules other than glucose are common
energy sources
Different pathways convert lipids and proteins to
substances that may enter glycolysis or the
Krebs cycle
7/30/2019 101pp Chapter 8
42/43
8.8 Reflections on Lifes Unity
Lifes diversity and continuity arise from unity at
the level of molecules and energy
Energy inputs drive the organization of molecules
into cells (one-way flow of energy)
Energy from the sun sustains lifes organization
Photosynthesizers use energy from the sun tofeed themselves and other forms of life
Aerobic respiration balances photosynthesis
Cycles Link Photosynthesis
7/30/2019 101pp Chapter 8
43/43
Cycles Link Photosynthesis
And Aerobic Respiration