1. Cellular respiration Fermentation Metabolism BMR
Refs in text
Ch 3.7
P335, Fig 14.15
Ch 14.11

2. Carbohydrate Metabolism
The body’s preferred source to produce cellular energy (ATP)
Glucose (blood sugar) is the major digestive product and serves as fuel to make ATP
Glucose is the ONLY energy source for the CNS.
Oxygen-using events take place within the cell to create ATP from ADP
Carbon leaves cells as carbon dioxide (CO2)
Hydrogen atoms are combined with oxygen to form water
Energy produced by these reactions adds a phosphorus to ADP to produce ATP
ATP can be broken down to release energy for cellular use
Figure 14.17

3. Metabolic Pathways Involved in Cellular Respiration
3 stages - note ATP production in each stage.
Glycolysis - small amount of ATP 2. Works even without O2. Anaerobically in muscles.
NAD taxi filled.
Krebs cycle - CO2 released here. What we exhale.
a bit more ATP 2. And more high-energy electrons. Fill the taxi with e- passengers. Shuttle over to electron transport chain.
ETChain. Slinky on stairs. Stepwise release of chemical energy. Captured in ATP 36. E passed to O2 to make water. So, this process needs oxygen. What we breathe in.
Figure 14.18

4. Glycolysis harvests chemical energy by oxidizing glucose to pyruvic acid
Figure 6.9A
Energy yield: 2 ATP and 2 NADH

5. Pyruvic acid is altered for the citric acid cycle
Acetyl CoA (acetyl coenzyme A)
Each pyruvic acid molecule is broken down to form CO2 and a two-carbon acetyl group, which enters the citric acid cycle
CO2
Figure 6.10

6. The citric acid cycle completes the oxidation of organic fuel
Acetyl CoA
enzymes convert acetyl to CO2 and generate NADH and FADH2 molecules 2
CITRIC ACID CYCLE
CO2
Figure 6.11A

7. Steps in the Electron Transport System
Rotenone binds to ETS carrier. Used to kill pest insects and fish. Similar blockage with cyanide and carbon monoxide. Shuts off “faucet” of ATP synthesis. Cells starve to death. Oligomycin blocks H+ from flowing thru ATP synthase. Used as antifungal agent on skin. Does not hurt dead skin cells on surface. Keratin keeps it from penetrating into living skin cells in deeper layers.
Uncouplers, Dinitrophenol, 1940s weight loss pill. Fuel is burned, but no ATP generated. Leads to death.
1. Set up H+ gradient using energy of e- from NADH, FADH2
2. Downhill flow of H+ is used to make ATP
Figure 3.28

8. cell
Figure: 07-06a Note the extra surface area provided by folds of inner membrane. More enzymes of ETS can be held. Note relatively smaller volume of intermembrane space, making it easier to create a large concentration gradient of H+.
Mitochondria are organelles, or “tiny organs,” that exist within cells. They are the location for the second and third sets of steps in cellular respiration, the Krebs cycle and the electron transport chain. Following a transitional step (see Figure 7.7), the products of glycolysis—the downstream products of the original glucose molecule—pass into the inner compartment of a mitochondrion, where the Krebs cycle takes place. Electrons derived from the Krebs cycle then migrate, via electron carriers, from the Krebs cycle site into the highly folded inner membrane of the mitochondrion, where the bulk of ATP is produced in the electron transport chain.
outer
membrane
inner
membrane
mitochondrion

9. An overview of cellular respiration
High-energy electrons carried by NADH
GLYCOLYSIS
ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS
CITRIC ACID CYCLE
Glucose
Pyruvic acid
2/2/32 ATP from each stage. Aerobic respiration much more efficient at harvesting chemical energy of glucose.
What happens if oxygen is not present?
Cytoplasmic fluid
Mitochondrion
Figure 6.8

10. Fermentation is an anaerobic alternative to aerobic respiration
Without oxygen, cells can use glycolysis alone to produce small amounts of ATP
But a cell must replenish NAD+
Glucose
Pyruvic acid

11. In lactic acid fermentation, pyruvic acid is converted to lactic acid
NAD+ is recycled
Contributes to muscle soreness
Lactic acid in muscle cells is sent via blood to liver, where it is converted back to pyruvic acid.
Yeast are facultative anaerobes, can go either way. Will choose aerobic resp if oxygen is present; ferment only if anaerobic. Different fermentation reaction: produces ethanol and CO2. Hence, large tanks for fermentation of beer, wine, that keep out air (oxygen).
GLYCOLYSIS
2 Pyruvic acid
2 Lactic acid
Glucose
Figure 6.15B

12. ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS
Pathways of molecular breakdown
Food, such as peanuts
Polysaccharides
Fats
Proteins
Sugars
Glycerol
Fatty acids
Amino acids
Amino groups
Pyruvic acid
ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS
Glucose
G3P
Acetyl CoA
CITRIC ACIDS CYCLE
GLYCOLYSIS
Figure 6.16

13. ATP needed to drive biosynthesis Cells, tissues, organisms
Biosynthesis of macromolecules from intermediates in cellular respiration
ATP needed to drive biosynthesis
GLUCOSE SYNTHESIS
CITRIC ACID CYCLE
Acetyl CoA
Pyruvic acid
G3P
Glucose
Amino groups
Amino acids
Fatty acids
Glycerol
Sugars
Proteins
Fats
Polyscaccharides
Cells, tissues, organisms
Figure 6.17

14. Body Energy Balance
Energy intake = total energy output (heat + work + energy storage)
Energy intake from food oxidation
Proteins, carbs have 4 Cal/gm
Fats have 9 Cal/gm
Energy output
Heat is usually about 60%
Storage energy is in the form of fat or glycogen

15. Regulation of Food Intake
Body weight is usually relatively stable
Energy intake and output remain about equal
Mechanisms that may regulate food intake
Levels of nutrients in the blood
Hormones: leptin, ghrelin
Body temperature
Psychological factors
Hormones that affect appetite. (contrast that with hormones that affect digestive process, such as gastrin, secretin, CCK)
Serotonin - causes decrease in appetite. Produced as result of exercise. Lack of exercise makes you hungry.
Leptin - secreted by adipose tissue in response to high-fat foods. Suppresses appetite
Ghrelin - apparently secreted by stomach cells, target is hypothalamus and stimulates appetite. Normally ghrelin levels rise before a meal, fall afterwards. Fasting causes increase in ghrelin levels.
Body temp - rise causes loss of appetite

16. Metabolic Rate and Body Heat Production
Basic metabolic rate (BMR) reflects the amount of energy spent per unit of time by a body at rest
Factors that influence BMR:
Body shape (height and weight), gender, body composition, age, stress, food intake, genetics
TMR = Total Metabolic Rate
Total energy spent, includes activity above BMR
Factors that influence BMR
Age – children and adolescents have a higher BMR
thyroxine is the major control factor, More thyroxine means higher metabolic rate
Gender, b/c males with higher % lean mass
Body composition - % fat, as adipose tissue consumes very few calories.
Age - usly increase in % fat
Stress - increases BMR
Food intake - starvation, fasting decreases BMR AND increases gain of weight after fasting stops. So “yo-yo” dieting makes it harder to lose each time.
Genetics - unclear exactly how it works in humans. Obese strains in mice now studied.
Total Metabolic Rate: Total amount of kilocalories the body must consume to fuel ongoing activities
TMR increases with an increase in body activity
TMR must equal calories consumed to maintain homeostasis and maintain a constant weight

17. Estimation of BMR
Johnson: your weight in kg (# lbs/2.2) x 24 (x 0.9 if female) = Calories per day
Your weight in kg (# lbs/2.2) x % lean mass males usually 82-88% females usually 75-82%
Then check table (next slide)

18. ESTIMATION OF RESTING METABOLIC RATE (RMR)
BASED ON FAT-FREE BODY MASS (FFM)
FFM RMR FFM RMR FFM RMR
(kg) (kcal) (kg) (kcal) (kg) (kcal)
Discuss accuracy and basis of the different methods.
What does BMR do? Maintain body temp, run heart, lungs, digestion
Surface area of body will affect how quickly you lose heat. Est surface area by height, wt.