Download Energy Metabolism - 35-206-202

ENERGY METABOLISM
CHAPTER 9
LEARNING OUTCOMES
• Explain the differences among metabolism,
catabolism and anabolism
• Describe aerobic and anaerobic metabolism of
glucose
• Illustrate how energy is extracted from glucose, fatty
acids, amino acids, and alcohol using metabolic
pathways, such as glycolysis, beta oxidation, the citric
acid cycle, and the electron transport system
• Describe the role that acetyl Co-A plays in cell
metabolism
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LEARNING OUTCOMES
• Identify the conditions that lead to
ketogenesis and it’s importance in
survival during fasting
• Describe the process of gluconeogenesis
• Compare the fate of energy from
macronutrients during the fed and fasted
state
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ENERGY METABOLISM
• All the macronutrients (CHO, FAT, PRO) and
EtOH provide energy, but not in the form our
bodies can use.
• What we will learn today is how we change
the energy from the food form you the form
we can use.
• We need the micronutrients to help out
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ANABOLIC OR CATABOLIC- IT MUST BE ONE OF
THE TW0
Catabolic pathways
Breakdown compounds
Into smaller units.
Anabolic pathways use
small, simpler
compound to build
larger, more
complex compounds.
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ENERGY FOR THE CELL
Why do we need energy?
• Contract muscles (cardiac, smooth, skeletal)
• Conducting nerve impulses
• Pumping ions (active diffusion)
Heat is a byproduct of catabolism- lucky for us!
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ENERGY FOR THE CELL
• Adenosine tri phosphate (ATP)
• The only source of energy the cell can use. It is
derived from catabolic reactions
• Adenosine di phosphate (ADP)
• Cells break high phosphate bond from ATP
• Adenosine mono phosphate (AMP)
• Hydrolysis of ADP used when ATP is in short supply
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ADENOSINE TRIPHOSPHATE
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ADENOSINE TRIPHOSPHATE
Hydrolysis of these
high-energy
bonds breaks the
bond and
release energy.
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WHERE DOES THIS ATP COME FROM?
ATP is made from ADP and Pi. Adding to Pi to the
ADP involves transferring energy from energyyielding compounds (CHO, FAT, PRO and EtOH),
The reactions that enable this to happen are called
oxidation-reduction reactions.
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OXIDATION-REDUCTION
Oxidized
Loses electrons by gaining oxygen or losing
hydrogen.
Reduced
Gains electrons by losing oxygen or gaining
hydrogen.
Electrons are the currency that are passed around to
make energy for the cell.
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CARBOHYDRATES
Aerobic and Anaerobic pathways are used to
make energy. When oxygen is present our
bodies can make 30-32 ATPs. Our bodies can
still make ATP when there is no oxygen available
but only 2 ATPs are produced for every
molecule of glucose.
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ATP PRODUCTION VIA CARBOHYDRATES
(AEROBIC)
1. Glycolysis
2. Synthesis of acetyl CoA
3. Citric Acid Cycle (CAC)
•
Acetyl CoA enters cycle producing ATP
4. The byproducts from steps 1-3 are used in a series
of oxidation reduction reactions in the
mitochondria of cells, this is where most ATP is
produced: The electron transport chain
ATP PRODUCTION VIA CARBOHYDRATES
(AEROBIC)
Step 1
Glycolysis- “breaking
down glucose”
This happens in the
cytoplasm of the cell.
Pyruvate is produced
from glucose.
Depends on B vitamins
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ATP PRODUCTION VIA CARBOHYDRATES
(AEROBIC)
Step 2
Now we are in the mitochondria.
Pyruvate is oxidized
(loses electrons) and
forms Acetyl-CoA and
NADH +2H+.
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ATP PRODUCTION VIA CARBOHYDRATES
(AEROBIC)
Step 3- The Citric Acid
Cycle (we’re still in the
mitochondria).
Acetyl-CoA enters the
citric acid cycle. In this
cycle ATP is produced
along NADH + H+ and
FADH2
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CITRIC ACID CYCLE
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ATP PRODUCTION VIA CARBOHYDRATES
(AEROBIC)
Step 4- The Electron
Transport Chain.
These byproducts (NADH + H+
and FADH2) that have been
made in step 1-3 now enter
the electron transport chain
and are oxidized. These
reactions account for most of
the ATP produced and require
oxygen.
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ELECTRON TRANSPORT SYSTEM
• Final pathway of aerobic respiration- makes
almost 90% of ATP produced from
catabolism of glucose
• Passage of electrons along a series of
electron carriers (oxygen is waiting at the
end to accept the electrons)
• Minerals involved
• Copper
• Iron
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ATP PRODUCTION VIA CARBOHYDRATES
(ANAEROBIC)
• Occurs in cells with no mitochondria or cells that
utilize it when there is no oxygen
• Pyruvate is converted to lactate (instead of AcetylCoA)
• Lactate is picked up the blood and delivered to
the liver
• Liver synthesizes compounds used in aerobic
metabolism from lactate
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ATP PRODUCTION VIA FATS
1. Lipolysis
• Triglycerides broken down into fatty acids and glycerol (this
happens in the GI tract).
• These triglycerides come from the foods we eat or from our
fat stores (body fat).
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ATP PRODUCTION VIA FATS
2. Fatty Acid Oxidation (fatty acids lose
electrons)
- Takes place in mitochondria
- Carnitine shuttles fatty acids from cytosol into
mitochondria
- In the mitochondria the fatty acids are converted
to Acetyl CoA. NADH + H+ and FADH2 are also
produced.
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ATP PRODUCTION VIA FATS
3. Acetyl CoA, NADH + H+ and FADH2 enter the
Citric Acid cycle and under co the same process that
the Acetyl CoA, NADH + H+ and FADH2 derived from
carbohydrates goes through.
One molecule of glucose can provide 30-22 ATPs. One
16-cardon fatty acid can produce 106 ATPs.
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CITRIC ACID CYCLE
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FAT METABOLISM
Carbohydrates aid fat metabolism by providing enough of key
substrates to keep the citric acid cycle going. If there are not
enough carbohydrates (glucose molecules) around to keep the
citric acid cycle going- fat metabolism cannot function normally.
“Fat burns in the flame of carbohydrate.”
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FAT METABOLISM
If the fatty acids cannot enter the citric acid cylce the
cannot be completely broken down and form Ketones.
Eventually our body can turn these ketones into
Acetyl-CoA which can then finally enter the citric acid
cycle.
• This process is called ketogenesis
• Ketosis in Diabetes Mellitus
• Ketosis in semistarvation or fasting or very low/no
carbohydrate diets.
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PROTEIN METABOLISM
• Proteins from food are broken down in to amino acids
(there are 20 amino acids)
• Energy metabolism occurs mostly in the liver (some amino
acids are metabolized in muscle tissue).
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PROTEIN METABOLISM
Step 1
• Deamination
• Lose the amine group from the amino acid
• Requires Vitamin B-6
• Carbon skeleton is left to enter CAC
• These amino groups are
• Converted to ammonia (toxic)
• Excreted in the urine
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PROTEIN METABOLISM
The 20 amino acids can fall into two categories:
• Glucogenic Amino Acid
• If the carbon skeleton can enter CAC directly or by
forming pyruvate –these carbons can eventually
become parts of glucose
• Ketogenic Amino Acid
• If carbon skeleton can become acetyl CoA, the carbon
skeletons do NOT become glucose
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ALCOHOL METABOLISM
Alcohol (EtOH) is
1. The enzyme alcohol dehydrogenase
converts EtOH to acetaldehyde and
NADH + H+
2. Acetaldehyde is converted to
acetyl-CoA which enters the CAC.
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REGULATION OF ENERGY METABOLISM
• ATP Concentrations
• High ATP
• Anabolic reactions
• High ADP
• Catabolic reactions
• Enzymes (ex. High protein diet increases synthesis of
enzymes needed for amino acid catabolism)
• Hormones (ex. Low insulin would promote
gluconeogenesis)
• Vitamins and Minerals (many needed for metabolic
pathways to operate)
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FASTING AND FEASTING
• Fasting encourages:
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Glycogen breakdown
Fat breakdown
Gluconeogenesis
Synthesis of ketone bodies
• Feasting encourages:
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Glycogen synthesis
Fat synthesis
Protein synthesis
Urea synthesis
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