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Krebs Cycle

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The citric acid cycle — also known as the tricarboxylic acid cycle (TCA cycle), the Krebs cycle, or the Szent-Györgyi–Krebs cycle[1][2] — is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidization of acetate derived from carbohydrates, fats and proteins into carbon dioxide.

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Myocyte

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A myocyte (also known as a muscle cell or muscle fiber)[1] is the type of cell found in muscle tissue. They are long, tubular cells that arise developmentally from myoblasts to form muscles

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Sarcomere

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A sarcomere (Greek sárx = "flesh", méros = "part") is the basic unit of a muscle. Muscles are composed of tubular muscle cells (myocytes or myofibers). Muscle cells are composed of tubular myofibrils. Myofibrils are composed of repeating sections of sarcomeres, which appear under the microscope as dark and light bands. Sarcomeres are composed of long, fibrous proteins that slide past each other when the muscles contract and relax.

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Myosin

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Myosins comprise a family of ATP-dependent motor proteins and are best known for their role in muscle contraction and their involvement in a wide range of other eukaryotic motility processes. They are responsible for actin-based motility.

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Actin

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Actin is a globular, roughly 42-kDa multi-functional protein found in all eukaryotic cells

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Eukaryote

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A eukaryote is an organism whose cells contain complex structures enclosed within membranes.

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amino acid

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biologically important organic compounds made from amine (-NH2) and carboxylic acid (-COOH) functional groups, along with a side-chain specific to each amino acid. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen.

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mitochondrion

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a membrane-enclosed organelle found in most eukaryotic cells.[1] These organelles range from 0.5 to 1.0 micrometer (μm) in diameter. Mitochondria are sometimes described as "cellular power plants" because they generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy.

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gluconeogenesis

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a metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates such as pyruvate, lactate, glycerol, and glucogenic amino acids.
It is one of the two main mechanisms humans and many other animals use to keep blood glucose levels from dropping too low (hypoglycemia). The other means of maintaining blood glucose levels is through the degradation of glycogen (glycogenolysis)

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glucagon

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Glucagon, a peptide hormone secreted by the pancreas, raises blood glucose levels. Its effect is opposite that of insulin, which lowers blood glucose levels.

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insulin

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Insulin is a peptide hormone, produced by beta cells of the pancreas, and is central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, skeletal muscles, and fat tissue to take up glucose from the blood. In the liver and skeletal muscles, glucose is stored as glycogen, and in adipocytes it is stored as triglycerides.

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peptide hormone

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Peptide hormones are proteins that have endocrine functions in living animals.

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adipocyte

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also known as lipocytes and fat cells, are the cells that primarily compose adipose tissue, specialized in storing energy as fat.

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islets of langerhans

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The islets of Langerhans are the regions of the pancreas that contain its endocrine (i.e., hormone-producing) cells.

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somatostatin

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also known as growth hormone-inhibiting hormone (GHIH) or somatotropin release-inhibiting factor (SRIF)) or somatotropin release-inhibiting hormone[citation needed] is a peptide hormone that regulates the endocrine system and affects neurotransmission and cell proliferation via interaction with G protein-coupled somatostatin receptors and inhibition of the release of numerous secondary hormones.

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Human Growth Hormone

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is a peptide hormone that stimulates growth, cell reproduction and regeneration in humans and other animals. It is a type of mitogen which is specific only to certain kinds of cells. Growth hormone is a 191-amino acid, single-chain polypeptide that is synthesized, stored, and secreted by somatotropic cells within the lateral wings of the anterior pituitary gland.

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prohormone

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A prohormone refers to a committed intra-glandular precursor of a hormone, usually having minimal hormonal effect by itself. The term has been used in medical science since the middle of the 20th century. Though not hormones themselves, prohormones amplify the effects of existing hormones. Examples of natural, human prohormones include proinsulin and pro-opiomelanocortin.

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Golgi Apparatus

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Part of the cellular endomembrane system, the Golgi apparatus packages proteins inside the cell before they are sent to their destination; it is particularly important in the processing of proteins for secretion.

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intrinsic factor

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also known as gastric intrinsic factor (GIF) is a glycoprotein produced by the parietal cells of the stomach. It is necessary for the absorption of vitamin B12 later on in the small intestine. In humans, the gastric intrinsic factor protein is encoded by the GIF gene

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parietal cell

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are the stomach epithelium cells that secrete gastric acid (HCl) and intrinsic factor in response to histamine (H2 receptor), acetylcholine (M3 receptors[1]) and gastrin (CCK2 receptors).

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stomach anatomy

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Cardia Where the contents of the esophagus empty into the stomach.
Fundus Formed by the upper curvature of the organ.
Body or Corpus The main, central region.
Pylorus The lower section of the organ that facilitates emptying the contents into the small intestine.

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pyloric gland

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The glands contain mucus cells and G cells that secrete gastrin.

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gastrin

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gastrin is a peptide hormone that stimulates secretion of gastric acid (HCl) by the parietal cells of the stomach and aids in gastric motility

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Digestion

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When food enters the mouth, its digestion starts by the action of mastication, a form of mechanical digestion, and the contact of saliva. Saliva, which is secreted by the salivary glands, contains salivary amylase, an enzyme which starts the digestion of starch in the food. After undergoing mastication and starch digestion, the food will be in the form of a small, round slurry mass called a bolus. It will then travel down the esophagus and into the stomach by the action of peristalsis. Gastric juice in the stomach starts protein digestion. Gastric juice mainly contains hydrochloric acid and pepsin. As these two chemicals may damage the stomach wall, mucus is secreted by the stomach, providing a slimy layer that acts as a shield against the damaging effects of the chemicals. At the same time protein digestion is occurring, mechanical mixing occurs by peristalsis, which are waves of muscular contractions that move along the stomach wall. This allows the mass of food to further mix with the digestive enzymes. A

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pericardium

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is a double-walled sac containing the heart and the roots of the great vessels.

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Layers of the heart

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The outer wall of the human heart is composed of three layers. The outer layer is called the epicardium, or visceral pericardium since it is also the inner wall of the pericardium. The middle layer is called the myocardium and is composed of cardiac muscle which contracts. The inner layer is called the endocardium and is in contact with the blood that the heart pumps.

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superior vena cava

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is a large diameter, yet short, vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium. It is located in the anterior right superior mediastinum.

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aorta

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is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it bifurcates into two smaller arteries

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3 metabolic pathways for glucose

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Glycogenesis - the conversion of excess glucose into glycogen as a cellular storage mechanism; this prevents excessive osmotic pressure buildup inside the cell
Glycogenolysis - the breakdown of glycogen into glucose, which provides a glucose supply for glucose-dependent tissues.
Gluconeogenesis - de novo synthesis of glucose molecules from simple organic compounds. an example in humans is the conversion of a few amino acids in cellular protein to glucose.

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catecholamine

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an organic compound that has a catechol (benzene with two hydroxyl side groups) and a side-chain amine. the most abundant catecholamines are epinephrine (adrenaline), norepinephrine (noradrenaline) and dopamine, all of which are produced from phenylalanine and tyrosine. Release of the hormones epinephrine and norepinephrine from the adrenal medulla of the adrenal glands is part of the fight-or-flight response.

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active transport

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he movement of a substance across a cell membrane against its concentration gradient (from low to high concentration)
Examples of active transport include the uptake of glucose in the intestines in humans and the uptake of mineral ions into root hair cells of plants.

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Phosphagen Energy System

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During short-term, intense activities, a large amount of power needs to be produced by the muscles, creating a high demand for ATP. The phosphagen system (also called the ATP-CP system) is the quickest way to resynthesize ATP (Robergs & Roberts 1997). Creatine phosphate (CP), which is stored in skeletal muscles, donates a phosphate to ADP to produce ATP: ADP + CP —© ATP + C. No carbohydrate or fat is used in this process; the regeneration of ATP comes solely from stored CP. Since this process does not need oxygen to resynthesize ATP, it is anaerobic, or oxygen-independent. As the fastest way to resynthesize ATP, the phosphagen system is the predominant energy system used for all-out exercise lasting up to about 10 seconds. However, since there is a limited amount of stored CP and ATP in skeletal muscles, fatigue occurs rapidly.

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Glycolysis

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Glycolysis is the predominant energy system used for all-out exercise lasting from 30 seconds to about 2 minutes and is the second-fastest way to resynthesize ATP. During glycolysis, carbohydrate—in the form of either blood glucose (sugar) or muscle glycogen (the stored form of glucose)—is broken down through a series of chemical reactions to form pyruvate (glycogen is first broken down into glucose through a process called glycogenolysis). For every molecule of glucose broken down to pyruvate through glycolysis, two molecules of usable ATP are produced (Brooks et al. 2000). Thus, very little energy is produced through this pathway, but the trade-off is that you get the energy quickly. Once pyruvate is formed, it has two fates: conversion to lactate or conversion to a metabolic intermediary molecule called acetyl coenzyme A (acetyl-CoA), which enters the mitochondria for oxidation and the production of more ATP (Robergs & Roberts 1997). Conversion to lactate occurs when the demand for oxygen is greater than

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Aerobic System

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The aerobic system—which includes the Krebs cycle (also called the citric acid cycle or TCA cycle) and the electron transport chain—uses blood glucose, glycogen and fat as fuels to resynthesize ATP in the mitochondria of muscle cells (see the sidebar “Energy System Characteristics”). Given its location, the aerobic system is also called mitochondrial respiration. When using carbohydrate, glucose and glycogen are first metabolized through glycolysis, with the resulting pyruvate used to form acetyl-CoA, which enters the Krebs cycle. The electrons produced in the Krebs cycle are then transported through the electron transport chain, where ATP and water are produced (a process called oxidative phosphorylation) (Robergs & Roberts 1997). Complete oxidation of glucose via glycolysis, the Krebs cycle and the electron transport chain produces 36 molecules of ATP for every molecule of glucose broken down (Robergs & Roberts 1997). Thus, the aerobic system produces 18 times more ATP than does anaerobic glycolysis from e

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Essential Amino Acids

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hystadine, icoleucine, leucine, lysine, methionine, phenyalanine, threonine, tryptophan, valine

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Nonessential amino acids

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alanine, arginine, aspartate, cysteine, glutamate, glutamine, glycine, proline, serine, tryosine, asparagine, selenocysteine

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Type I Fibers (slow oxidative)

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contain large amounts of myoglobin and have many mitochondria. Resistant to fatigue. AKA slow twitch. split ATP at a slow rate, meaning they have the ability to refuel during aerobic activity.

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Type II A Fibers (fast oxidative)

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fast twitch. red and have a very high capacity for generating ATP. Type II A msucle fibers have a fast contraction velocity and can utilize aerobic metabolism, as a means of generating energy.

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Type II B Fibers (fast glycolytic fibers)

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type II B fibers are also called fast twitch, but these fibers are white and have little capacity for endurance, as they fatigue easily. Most explosive; high levels of creatine phosphate and glycogen, making them very powerful.