Eko Widodo
Metabolism
Energy Metabolism
◦ The sum total of all the chemical reactions that go on in living cells ◦ Includes all the reactions by which the body obtains & spends energy from food
Metabolic reactions take place inside cells, especially liver cells
Anabolism is the building up of body
compounds and requires energy. Catabolism is the breakdown of body compounds and releases energy.
→ glucose From fats → glycerol & FA From proteins → AA
From CHO
4 basic units used in metabolic pathway
Alcohol can disrupt normal metabolic pathways (Highlight 7)
ATP – adenosine triphosphate ◦ High-energy storage compound ◦ Captures some energy released during breakdown of glucose, glycerol, fatty acids, and amino acids
Hydrolysis of ATP occurs simultaneously with reactions that will use that energy ◦ Coupled reactions ◦ Energy released from breakdown of one compound used to create bond in formation of another
Co-enzymes are organic molecules that work with enzymes to facilitate their activity. Enzymes & co-enzymes are helpers in metabolic reactions. Some B vit serve as coenzymes to enzymes that release energy from glucose, glycerol, FA & AA.
Basic units enter metabolic pathways. During catabolism, the body separates atoms of basic units. ◦ ◦ ◦ ◦
Glucose: 6 C Glycerol: 3 C FA: even number of C (commonly 16 or 18) AA: 2, 3 or more C, with N attached
While each starts down a different path – 2 byproducts are common ◦ pyruvate & acetyl-coA
Eventually all enter the TCA cycle & electron transport chain
Glucose splitting 6-C Glucose → two 3-C compounds → Pyruvate Glucose anaerobic
Pyruvate
If cell needs energy (& O2 is available), it removes COOH group from pyruvate to produce 2 C compounds that bonds with CoA to form Acetyl CoA aerobic
Pyruvate anaerobic
Pyruvate
Lactate
Acetyl CoA
Absence of sufficient O2 (or mitochondria) pyruvate is converted to lactic acid
Lactate recycled to glucose in liver by Cori cycle
3-C glycerol is easily converted to pyruvate Also easily converted to glucose
Glucose
Glycerol
Pyruvate
FA are taken apart in 2-C units through fatty acid oxidation. 2-C units split off & combine with CoA to form Acetyl CoA. If cell doesn’t need energy, acetyl CoA molecules combine to create TG.
PROTEIN AND AMINO ACID METABOLISM ENVIRONMENT
ORGANISM
Biosynthesis
Ingested protein
2
1
Protein 3
a AMINO ACIDS
c
b
c
Purines Pyrimidines Porphyrins
Degradation (required) Carbon skeletons
Nitrogen (ketogenic) Urea acetoacetate acetyl CoA
(glucogenic) Used for energy
pyruvate α-ketoglutarate succinyl-CoA fumarate oxaloacetate
Deaminated first (lose N)
Catabolized in a variety of ways: ◦ Pyruvate glucose ◦ Acetyl CoA more energy or body fat ◦ Directly into TCA Cycle generate energy
Amino Acid Requirements of Humans -------------------------------------------------------------------Nutritionally Essential Nutritionally Nonessential -------------------------------------------------------------------Argininea Alanine Histidine Asparagine Isoleucine Aspartate Leucine Cysteine Lysine Glutamate Methionine Glutamine Phenylalanine Glycine Threonine Proline Tryptophan Serine Valine Tyrosine --------------------------------------------------------------------a “ Nutritionally semiessential.” Synthesized at rates inadequate to support growth of children.
NITROGEN BALANCE Nitrogen balance = nitrogen ingested - nitrogen excreted (primarily as protein) (primarily as urea) Nitrogen balance = 0 (nitrogen equilibrium) protein synthesis = protein degradation Positive nitrogen balance protein synthesis > protein degradation Negative nitrogen balance
protein synthesis < protein degradation
Amino Acids ◦ Deamination results in two products: Keto acid Ammonia
◦ Transamination is the transfer of the amino group from an amino acid to a keto acid. ◦ Ammonia is converted to urea—a much less toxic compound—in the liver. ◦ Urea is excreted through the kidneys to rid the body of unused nitrogen.
UREA CYCLE
mitochondria cytosol
Function: detoxification of ammonia (prevents hyperammonemia)
FATE OF THE CARBON SKELETONS Carbon skeletons are used for energy.
Glucogenic: TCA cycle intermediates or pyruvate (gluconeogensis)
Ketogenic: acetyl CoA, acetoacetyl CoA, or acetoacetate
In Summary
◦ Glucose and fatty acids are primarily used for energy, amino acids to a lesser extent. ◦ Glucose is made from all carbohydrates, most amino acids and the glycerol portion of fat. ◦ Protein is made from amino acids. ◦ Glucose can be made into nonessential amino acids if nitrogen is present. ◦ All energy-yielding nutrients consumed in excess can contribute to fat storage.
TCA Cycle – tricarboxylic acid cycle (aka Kreb’s cycle)
Oxaloacetate picks up acetyl CoA & drops off 2-C & returns to pick up another acetyl CoA.
As acetyl CoA breaks to CO2, H atoms with their electrons are removed. Coenzymes made from B vitamins take H & electrons & transfers them to ETC.
Electron Transport Chain (ETC) Consist of a series of proteins that serve as electron carriers. These carriers are inside inner membrane of mitochondria. In ETC, energy is captured in bonds of ATP molecules. ATP leaves mitochondria & enters cytoplasm, where it can be used for energy.
Each ATP holds energy & Kcal measures energy, so the more ATP generated the more Kcal collected. ◦ One glucose molecule yield 36-38 ATP when oxidized completely. ◦ One 16 carbon FA yield 129 ATP when oxidized completely.
When energy intake exceeds energy output, there is a gain in weight. Fat cells enlarge & multiply regardless of whether the excess comes from protein, CHO or fat. Most direct & efficient pathway to body fat is dietary fat.
Body needs energy all the time Relies on energy stores between meals ◦ glycogen ◦ fatty acids ◦ lean mass tissue .. least preferred
Fasting—Inadequate Energy ◦ Glucose needed for the brain ◦ Protein meets glucose needs ◦ The shift to ketosis
Ketones are produces when glucose is not available.
◦ Ketosis causes a suppression of the appetite. ◦ Slowing of metabolism
Fasting—Inadequate Energy ◦ Symptoms of starvation
Muscle wasting Decreased heart rate, respiratory rate, metabolic rate, and body temperature Impaired vision Organ failure Decreased immunity Depression, anxiety, and food-related dreams
Buatlah resume: 1. Diagram metabolisme protein dan berikan penjelasannya 2. Diagram metabolisme karbohidrat (glikolisis) dan berikan penjelasannya
