Transcript Cell Respiration and Metabolism

CHAPTER 5
Cell Respiration and Metabolism
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Glycolysis
Lactic Acid Pathway
Krebs Cycle
ATP Production
Basal Metabolic Rate (not in your book)
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.
Glycolysis
Glycolysis = Breakdown of glucose to obtain energy.
Nicotinamide Adenine Dinucleotide
Glucose + 2NAD + 2ADP + 2 Pi
Adenosine Diphosphate
Glycolysis cccurs
in cell cytoplasm
2 Pyrovic Acid + 2NADH + 2ATP
Adenosine Triphosphare
Glycolysis
-1
-1
+2
+2
Glucose
2 ATP
ENERGY LEVEL
2 NADH
+ 2 ADP + 2 Pi
+ 2NAD
2 Pyrovic Acid
Glycolysis
Phosphorylation of glucose to
glucose-6 phosphate traps
glucose inside the cell.
Lactic Acid Pathway
Glycolysis
Glucose
In the absence of oxygent
• Anerobic respiration or Lactic acid Fermentation
Glycogenesis and Glycogenolysis
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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.
ADP
ATP
Glucose-1-phosphate
Glucose-6-phosphate
Glucose
Enzyme
Enzyme
Pi
Enzyme
Glycogen
Breakdown of glycogen to glucose is called glycogenolysis.
Pi
Glucose-6-phosphate
Glucose-1-phosphate
Glycogen
Enzyme
Enzyme
Only in LIVER
Enzyme
Glucose
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.
Cori Cycle
Glycolysis
Lactic Acid
Pathway
2 ATP
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
Aerobic Respiration
Glycolysis
Glucose
Main Events in Krebs Cycle
• 1- One guanosin triphosphate (GTP) is produced, which gives a
phosphate group to ADP to produce one ATP.
2ATP/glucose
• 2- Three molecules of NAD are reduced to NADH
• 3- One molecule of FAD is reduced to FADH2.
6NADH/glucose
2FADH2/glucose
• The production of NADH and FADH2 are far more significant in
terms of energy production than GTP production.
Flavin Adenine Dinucleotide
Chemiosmotic Theory
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.
Net ATP production from Glucose
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
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.
In an aerobic respiration one L of O2:
+ Carbohydrates
+ Proteins
+ Fat
Therefore 1L of O2 + mixed food
5.06 Calories
4.60 Calories
4.70 Calories
4.825 Calories
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.
Methods for Measuring Metabolic rate
1- Direct Method:
Thermometer
Calorimeter
Methods for Measuring Metabolic rate
2- Indirect Method:
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.Means for each L of O2
the subject’s body surface area is 1.5 m2,
4.8 Calories heat is produced
What is this subject’s BMR?
15 x 4.8 = 72.4 Calories/hr
72.5
1.5
= 48.3 calories/m2/hr
Heat loss from the Body
- Heat is lost from the body by: Radiation, Conduction and Evaporation
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.