Cell Respiration and Metabolism

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Cell Respiration and Metabolism
CHAPTER 5

• Glycolysis
• Lactic Acid Pathway
• Krebs Cycle
• ATP Production
• Basal Metabolic Rate (not in your book)

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Metabolism

• Metabolism all of the reactions in the body
  that involve energy transformation are
  
  
  collectively termed metabolism.

Metabolism 1- Anabolism the process of using
energy to build up larger molecules. Here some
of the energy used is stored in the new molecule.
e.g. synthesis of glycogen, fat, and
protein. 2- Catabolism the process of
releasing energy from larger food molecules by
converting them into smaller molecules. e.g.
breakdown of glucose, fatty acids, and amino
acids and formation of ATP in the process.
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Glycolysis

• Glycolysis Breakdown of glucose to obtain
  energy.

Glucose 2NAD 2ADP 2 Pi
Glycolysis cccurs in cell cytoplasm
2 Pyrovic Acid 2NADH 2ATP
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Glycolysis
-1
-1
2
2
5
2 ATP
2 NADH
Glucose
2 ADP 2 Pi
E N E R G Y L E V E L
2 Pyrovic Acid
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Glycolysis
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Lactic Acid Pathway
Glycolysis

• Anerobic respiration or Lactic acid Fermentation

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Glycogenesis and Glycogenolysis

• Cells can not accumulate free glucose because of
  osmotic effect which causes the water to enter
  the cell.
• So glucose is stored in the form of glucose
  polymeres (Glycogen), particularly in liver,
  skeletal muscle and heart.
• Formation of glycogen from glucose is called
  glycogenesis.

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Glycogenesis and Glycogenolysis

• Blood glucose that enters tissue cells is
  rapidly converted to glucose-6-phosphate. This
  intemediate can be metabolized for energy in
  glycolysis, or it can be converted to glaycogen
  (1) in a process called glycogenesis. Glycogen
  represents a storage form of carbohydrates which
  can be used as a new source of glucose (2) by
  glycogenolysis.

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Cori Cycle
2 ATP
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Aerobic Cell Respiration

• Conversion of molecules such as glucose or fatty
  acid to CO2 H2O in the presence of O2 is called
  aerobic cell respiration.

O2
CO2 H2O ATP HEAT
Glucose
ENZYMES
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Aerobic Respiration
Glycolysis
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Main Events in Krebs Cycle

• 1- One guanosin triphosphate (GTP) is produced,
  which gives a phosphate group to ADP to produce
  one ATP.
• 2- Three molecules of NAD are reduced to NADH
• 3- One molecule of FAD is reduced to FADH2.
• The production of NADH and FADH2 are far more
  significant in terms of energy production than
  GTP production.

2ATP/glucose
6NADH/glucose
2FADH2/glucose
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Chemiosmotic Theory
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Oxidative Phosphorylation

• ATP is formed during oxidative phosphorylation by
  the flow of hydrogen ions across the inner
  mitochondrial membrane.
• Two or three molecules of ATP are produced per
  pair of electrons donated, depending on the point
  at which a particular coenzyme enters the
  electron-transport chain.

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Net ATP production from Glucose
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Heat Production in the Body
- Metabolic activity occurs in all cells of the
body, therefore all cells are involved in the
production of heat but there are certain tissues
which produce more heat than others - Tissues
with highest heat production - Liver -
Brain - Endocrine Glands - Skeletal muscle
during exercise
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Metabolic rate

• Metabolic rate the total rate of body
  metabolism. Body metabolism is measured by
  Calories.
• - One calorie is defined as the amount of heat
  required to raise the temperature of one cubic
  centimeter of water from 14.5 degrees to 15.5
  degrees centigrade.

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Basal Metabolic rate (BMR)

• The metabolic rate of an awake, relaxed person
  12-14 hours after eating and at a comfortable
  temperature is known as Basal Metabolic Rate
  (BMR).
• BMR is determined by age, sex, body surface
  area, and thyroid hormone secretion.

Basal conditions can be achieved by 1-
Avoiding exercise for at least 30 minutes before
measuring BMR. 2- Complete mental rest. 3-
Comfortable temperature. 4- Fasting for at least
12 hours. 5- Body temperature must be normal.
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Methods for Measuring Metabolic rate
1- Direct Method
Thermometer
Calorimeter
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Methods for Measuring Metabolic rate
2- Indirect Method
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Units of Metabolic rate

• - Metabolic rate is measured as
• Calories per square meter per hour
  (Calories/m2/hr)
• m2 is the measure of body surface area.

As an example BMR can be calculated from the
amount of O2 consumption A subject consumes 15
L of O2 in 1 hour at basal conditions, Caloric
equivalent of O2 is 4.8 Calories/L. the
subjects body surface area is 1.5 m2, What is
this subjects BMR?
Means for each L of O2 4.8 Calories heat is
produced
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Heat loss from the Body

• Heat is lost from the body by Radiation,
  Conduction and Evaporation

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Body Temperature

• The body maintains its temperature around 37 oC
  which is the optimum
• for enzymes and biological reactions.
• - To achieve this body must balance between heat
  production and heat loss.