Download 2 ATP - The Driggers Dirt

Chapter 8
 How Cells Release Chemical Energy
Overview of Energy Releasing
Pathways
 All organisms release chemical bond energy
from glucose and other organic compounds
to drive ATP formation.
 The main energy releasing pathways all
start in the cytoplasm.
 Only aerobic respiration, which uses O,
ends in the mitochondria.
 It has the greatest energy production.
2
Cont.
 Plants make ATP during photosynthesis
and use it to synthesize glucose and
other carbohydrates.
 But all organisms, plants included, can
make ATP by breaking down
carbohydrates, lipids, and proteins.
3
Comparison of the main
types of energy releasing
pathways
 ATP can be made by aerobic or anaerobic
mechanisms (with or without oxygen).
 The first organisms on earth would have used
anaerobic respiration since O was not readily
available.
 Aerobic respiration is an efficient way to covert
glucose to ATP
 The pathways starts in the cytoplasm called
glycolysis
4
cont
 Glycolysis converts glucose to 2 pyruvate
compounds
 If oxygen is present then aerobic
respiration proceeds - the pyruvate
enters the mitochondria. If no oxygen is
present the process stays in the
cytoplasm.
5
Overview of Aerobic
Respiration
 More ATP is generated by aerobic
respiration – yields 36 or more
 Anaerobic respiration (without oxygen)
has a very low yield and only yields 2
ATP molecules
6
 Aerobic respiration steps:
Step 1--Glycolysis in cytoplasm, take 2
ATP to start then process; produces
2 pyruvates , electrons, hydrogen,
and produces 4 ATP – a net of 2 ATP
7
 Step 2--Krebs cycle breaks down
pyruvate to carbon dioxide, e- & H+,
and 2 ATP. The Krebs cycle takes
place in the mitochondria.
 Step 3—Electron transfer
phosphorlation; membrane proteins
generate 32 ATP, water by using
oxygen as last e- acceptor. Takes
place across membranes in the
mitochondria.
Summary Equation for
Aerobic Respiration
C6H1206 + 6O2
glucose
oxygen
6CO2 + 6H20
carbon
water
dioxide
10
Glucose
 A simple
sugar
(C6H12O6)
 Atoms held
together by
covalent
bonds
11
CYTOPLASM
2
glucose
ATP
4
Glycolysis
e- + H+
(2 ATP net)
2 pyruvate
2 NADH
2 NADH
8 NADH
2 FADH2
e-
ATP
e- + H+
2 CO2
e- + H+
e-
+
Krebs
Cycle
H+
Electron
Transfer
Phosphorylation
H+
4 CO2
2
ATP
32
ATP
water
e- + oxygen
Typical Energy Yield: 36 ATP
12
Glycolysis –
Glucose Breakdown Starts
 Glycolysis is the first stage of aerobic
respiration.
 It is also the first stage in anaerobic
respiration, such as alcoholic and
lactate (lactic acid) fermentation.
13
Importance of Oxygen
 Electron transport phosphorylation
requires the presence of oxygen
 Oxygen withdraws spent electrons from
the electron transfer chain, then
combines with H+ to form water
14
15
Fermentation Pathways
 Without Oxygen or do not use oxygen –
anaerobic
 Step 1 – Glycolysis in cytoplasm
 2 pyruvates
 2 Net ATP
 2 NADH
 Step 2 – Fermentation
 No more ATP is made only new end
products
16
Alcoholic fermentation
 This pyruvic acid is then converted to CO2, ethanol, and
energy for the cell.
 Humans have long taken advantage of this process in
making bread, beer, and wine.
 Yeast :
 in wheat & grains–
 sugar is converted into alcohol and carbon dioxide.
 The carbon dioxide will form bubbles, which will be
trapped by the gluten of the wheat causing the bread to
rise.
 small amounts of alcohol are formed, most of which will
be evaporated during the bread baking process.
Therefore, you won’t get drunk by eating bread!
17
Cont.
• In Grapes –
 produces ethanol at about 10% it kills yeast;
 Saccharomyces is responsible for the
alcohol fermentation of wines.
 Grape juice contains naturally high levels of
sugars.
 These sugars are converted into alcohol and
carbon dioxide.
18
Lactate fermentation
 Ex. Food – Lactobacillus & other
bacteria spoil food, some help make
milk products; pickling –(sauerkraut)
19
 Ex. Muscles – ATP produced quickly, short term
 DURING EXERCISE, BREATHING CANNOT
PROVIDE YOUR BODY WITH ALL THE
OXYGEN IT NEEDS FOR AEROBIC
RESPIRATION.
 WHEN MUSCLES RUN OUT OF OXYGEN, THE
CELLS SWITCH TO LACTIC ACID
FERMENTATION.
 Blood removes Lactic Acid from muscles, but if it
is not removed fast enough, the side effects of
Lactic Acid Fermentation is Muscle Fatigue, Pain,
Cramps, and Soreness.
 Most Lactic Acid made in the muscles diffuse into
the bloodstream, then to the LIVER, where it is
converted back to PYRUVIC ACID When Oxygen
20
becomes Available.
Lactate Fermentation
GLYCOLYSIS
C6H12O6
2
ATP
energy input
2 NAD+
2 ADP
2
4
NADH
ATP
energy output
2 pyruvate
2 ATP net
LACTATE
FORMATION
electrons, hydrogen
from NADH
2 lactate
21
Alterative Energy Sources in the
Body
 When required, molecules other than
glucose can enter the aerobic pathways
as alternative energy sources.
 Cells must deal with too much or too little
glucose.
22
Fate of Glucose at mealtime &
between Meals
 Glucose  enter cell (at prompting of
insulin) glucose-6-phosphate– trapped
in cell
 If cells are not using up glucose rapidly it
is converted to glycogen
(polysaccharide) in the liver & muscles of
animals
 Between meal glucose levels drop 
pancreas secrete glucagon converts
23
glycogen in liver to glucose.
Processes Are Linked
sunlight energy
PHOTOSYNTHESIS
water
+
carbon
dioxide
sugar
molecules
oxygen
AEROBIC
RESPIRATION
24