which break down large chemicals and release energy
which build up large chemicals and require energy
the steady-state of the internal environment is known homeostasis and includes regulation by hormones and the nervous system
Irritability is the ability to respond to a stimulus and is part of the regulation.
the net reaction of glycolysis
the net reaction of citric acid cycle
Pyruvate degradation can proceed
under anaerobic condition, pyruvate is reduced
Under aerobic condition, pyruvate oxidized in mitochondria
Only in yeast and some bacteria
Pyruvate is converted to ethanol
Lactic acid formation
In certain fungi and bacteria and in human muscle cells during strenuous activity.
NAD is regenerated and is used in step 5
36-38 ATPs are produced
Oxygen is the final acceptor pof electrons
Stages of the cellular respiration
- Pyruvate decarboxylation
- The citric acid cycle
- Electron transport chain
Pyruvate is decarboxylated in mitochondria ( it loses CO2)
NAD is reduced to NADH
Acetyl group is transferred to coenzyme A to form Acrtyl-CoA
Coenzyme A is a derivative of pantothenic acid (a B vitamin)
Citric acid cycle
Acetyl-CoA(2C) combines with oxaloacetate(4C) to form six carbon citrate
2ATP is produced by substrate-level phosphorylation via GTP intermediate
2acetyl-CoA + 6NAD + 2FAD + 2GDP + 2Pi + 4H2O >>>> 4CO2 + 6NADH + 2FADH2 + 2GTP + 4H + 2CoA
Electron transport chain (ETC)
Occurs on the inside of the inner mitochondrial membrane
During oxidative phosphorylation, ATP is produced when high-energy potential electrons are transferred from NADH and FADH2 to oxygen by a series of carrier molecules located in the inner mitochondrial membrane.
Electron carriers that resemble hemoglobin in the structure of their active site.
The functional unit contains a central iron atom that is capable of undergoing a reversible redox reaction.
Electrons are transferred from one carrier to the next, each carrier is reduced as it accepts an electron and is then oxidized when it passes it on to the next carrier.
2H* + 2e- + 1/2O2>>>> H2O
The last carrier of ETC passes its electron to the final electron acceptor, O2
In addition to electrons, O2 picks up a pair of hydrogen ions from the surrounding medium, forming water
Pump of hydrogen
- Series of protein complexes (cytochromes) in the cristae of the mitochondria
- Electrons are passed through the cytochromes and lose energy
- This energy is used to pump hydrogen ions from the matrix to the intermembrane space.
- As the hydrogen ions pass through channels in the respiratory enzymes,the energy created used to convert ADP to ATP.
Number of ATP production
Net 2ATP, 2NADH × 2ATP/NADH. = 6ATP
2. Pyruvate decarboxylation
2 NADH × 3 ATP/NADH = 6 ATP
3. Citric acid
6 NADH × 3ATP/NADH, 2 FADH2 × 2ATP/FADH2, 2GTP × 1ATP/ GTP = 24.
TOTAL 36 ATP
4 ATP is produced by substrate
alternate energy source : Carbohydrate
Disaccharides are hydrolyzed into monosaccharides, can convert glucose or glucose intermediate
Glycogen stored in the liver can be converted , when needed, into a glycolytic intermediate
alternate energy source : Fat
fat molecules are stored in adipose tissue in the form of triglycerides.
When needed, they are hydrolyzed by lipases to fatty acids and glycerol and carry by blood to other tissues for oxidation.
How Glycerol enters to glycolysis
Glycerol can be converted into PGAL, a glycolytic intermediate
How fatty acid enters to glycolysis
Fatty acid must first be activated in the cytoplasm, this process requires two ATP.
ONCE ACTIVATED, it is transported into the mitochondrion and taken through a series of beta-oxidation cycle that convert it into two-carbon fragments which are then converted into acetyl-CoA that can enters the citric acid cycle.
With each round of beta-oxidation of a saturated fatty acid, one NADH and one FADH2a are generated.
Fat and glycogen
The amount of glycogen stored in humans is enough to meet the short-term energy needs of about a day
The stored fat reserves can meet the long-term energy needs for about a month.
The body degrates proteins only when not enough carbohydrate or fat is available.
Most amino acid undergo a transamination reaction in which they lose an amino group to form an alpha-keto acid. The carbon atoms of most amino acids are converted into acetyl-CoA, pyruvatw or one of the intermediate of the citric acid cycle.
These intermediates enter their respective metabolic pathways, allowing cells to produce fatty acids, glucose, or energy in the form of ATP
Removes an ammonia molecule from the amino acid.
Ammonia is a toxic substance in vertebrates. Fish can excrete ammonia,whereas insects and birds convert it to uric acid, and mammal convert it to urea for excretion.
energy is stored in ATP as high-energy bonds
created by the covalent bonding of three phosphates to adenosine, the hydrolysis of ATP to ADP releases inorganic phosphate and 7 Kcal, hydrolysis of ADP to AMP release additional 7 Kcal