Glycogen

Schematic two-dimensional cross-sectional view of glycogen: A core protein of glycogenin is surrounded by branches of glucose units. The entire globular granule may contain around 30,000 glucose units.
A view of the atomic structure of a single branched strand of glucose units in a glycogen molecule.
Glycogen (black granules) in spermatozoa of a flatworm; transmission electron microscopy, scale: 0.3 μm
1,4-α-glycosidic linkages in the glycogen oligomer
1,4-α-glycosidic and 1,6-glycosidic linkages in the glycogen oligomer
Action of glycogen phosphorylase on glycogen

Multibranched polysaccharide of glucose that serves as a form of energy storage in animals, fungi, and bacteria.

- Glycogen
Schematic two-dimensional cross-sectional view of glycogen: A core protein of glycogenin is surrounded by branches of glucose units. The entire globular granule may contain around 30,000 glucose units.

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The fluctuation of blood sugar (red) and the sugar-lowering hormone insulin (blue) in humans during the course of a day with three meal. One of the effects of a sugar-rich vs a starch-rich meal is highlighted.

Blood sugar level

Measure of glucose concentrated in the blood of humans or other animals.

Measure of glucose concentrated in the blood of humans or other animals.

The fluctuation of blood sugar (red) and the sugar-lowering hormone insulin (blue) in humans during the course of a day with three meal. One of the effects of a sugar-rich vs a starch-rich meal is highlighted.

Glucose is stored in skeletal muscle and liver cells in the form of glycogen; in fasting individuals, blood glucose is maintained at a constant level at the expense of glycogen stores in the liver and skeletal muscle.

Structure of the amylose molecule

Starch

Polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds.

Polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds.

Structure of the amylose molecule
Structure of the amylopectin molecule
Starch mill at Ballydugan (Northern Ireland), built in 1792
West Philadelphia Starch works at Philadelphia (Pennsylvania), 1850
Faultless Starch Company at Kansas City
potato starch granules in cells of the potato
starch in endosperm in embryonic phase of maize seed
Corn starch, 800x magnified, under polarized light, showing characteristic extinction cross
Rice starch seen on light microscope. Characteristic for the rice starch is that starch granules have an angular outline and some of them are attached to each other and form larger granules
Granules of wheat starch, stained with iodine, photographed through a light microscope
Sago starch extraction from palm stems
Glucose syrup
Karo corn syrup advert 1917
Niagara corn starch advert 1880s
Pacific Laundry and Cooking Starch advert 1904
Starch adhesive
Gentleman with starched ruff in 1560
Kingsford Oswego Starch advertising, 1885
Rice starch for ironing

Glycogen, the energy reserve of animals, is a more highly branched version of amylopectin.

Insulin is a peptide hormone containing two chains cross-linked by disulfide bridges.

Insulin

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Insulin is a peptide hormone containing two chains cross-linked by disulfide bridges.
Diagram of insulin regulation upon high blood glucose
Insulin undergoes extensive posttranslational modification along the production pathway. Production and secretion are largely independent; prepared insulin is stored awaiting secretion. Both C-peptide and mature insulin are biologically active. Cell components and proteins in this image are not to scale.
The structure of insulin. The left side is a space-filling model of the insulin monomer, believed to be biologically active. Carbon is green, hydrogen white, oxygen red, and nitrogen blue. On the right side is a ribbon diagram of the insulin hexamer, believed to be the stored form. A monomer unit is highlighted with the A chain in blue and the B chain in cyan. Yellow denotes disulfide bonds, and magenta spheres are zinc ions.
Insulin release from pancreas oscillates with a period of 3–6 minutes.
The idealized diagram shows the fluctuation of blood sugar (red) and the sugar-lowering hormone insulin (blue) in humans during the course of a day containing three meals. In addition, the effect of a sugar-rich versus a starch-rich meal is highlighted.
Effect of insulin on glucose uptake and metabolism. Insulin binds to its receptor (1), which starts many protein activation cascades (2). These include translocation of Glut-4 transporter to the plasma membrane and influx of glucose (3), glycogen synthesis (4), glycolysis (5) and triglyceride synthesis (6).
The insulin signal transduction pathway begins when insulin binds to the insulin receptor proteins. Once the transduction pathway is completed, the GLUT-4 storage vesicles becomes one with the cellular membrane. As a result, the GLUT-4 protein channels become embedded into the membrane, allowing glucose to be transported into the cell.
Two vials of insulin. They have been given trade names, Actrapid (left) and NovoRapid (right) by the manufacturers.
Charles Best and Clark Noble ca. 1920
Chart for Elizabeth Hughes, used to track blood, urine, diet in grams, and dietary prescriptions in grams
Frederick Banting (right) joined by Charles Best 1924
Nicolae Paulescu

In these tissues the absorbed glucose is converted into either glycogen via glycogenesis or Fatty fats (triglycerides) via lipogenesis, or, in the case of the liver, into both.

Simplified gluconeogenesis pathway (as occurs in humans). Acetyl-CoA derived from fatty acids (dotted lines) may be converted to pyruvate to a minor extent under conditions of fasting.

Gluconeogenesis

Metabolic pathway that results in the generation of glucose from certain non-carbohydrate carbon substrates.

Metabolic pathway that results in the generation of glucose from certain non-carbohydrate carbon substrates.

Simplified gluconeogenesis pathway (as occurs in humans). Acetyl-CoA derived from fatty acids (dotted lines) may be converted to pyruvate to a minor extent under conditions of fasting.
Catabolism of proteinogenic amino acids. Amino acids are classified according to the abilities of their products to enter gluconeogenesis:
Gluconeogenesis pathway with key molecules and enzymes. Many steps are the opposite of those found in the glycolysis.

It is one of two primary mechanisms – the other being degradation of glycogen (glycogenolysis) – used by humans and many other animals to maintain blood sugar levels, avoiding low levels (hypoglycemia).

Hepatocyte and sinusoid (venule) in a section of rat liver

Hepatocyte

Protein synthesis

Protein synthesis

Hepatocyte and sinusoid (venule) in a section of rat liver
Schemic diagram of Biliary system

Brown lipofuscin granules are also observed (with increasing age) together with irregular unstained areas of cytoplasm; these correspond to cytoplasmic glycogen and lipid stores removed during histological preparation.

Metabolic regulation of glycogen by glucagon.

Glucagon

Peptide hormone, produced by alpha cells of the pancreas.

Peptide hormone, produced by alpha cells of the pancreas.

Metabolic regulation of glycogen by glucagon.
A microscopic image stained for glucagon

Glucagon causes the liver to engage in glycogenolysis: converting stored glycogen into glucose, which is released into the bloodstream.

Lactose is a disaccharide found in animal milk. It consists of a molecule of D-galactose and a molecule of D-glucose bonded by beta-1-4 glycosidic linkage.

Carbohydrate

Biomolecule consisting of carbon , hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula Cm(H2O)n (where m may or may not be different from n).

Biomolecule consisting of carbon , hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula Cm(H2O)n (where m may or may not be different from n).

Lactose is a disaccharide found in animal milk. It consists of a molecule of D-galactose and a molecule of D-glucose bonded by beta-1-4 glycosidic linkage.
D-glucose is an aldohexose with the formula (C·H2O)6. The red atoms highlight the aldehyde group and the blue atoms highlight the asymmetric center furthest from the aldehyde; because this -OH is on the right of the Fischer projection, this is a D sugar.
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Glucose can exist in both a straight-chain and ring form.
Sucrose, also known as table sugar, is a common disaccharide. It is composed of two monosaccharides: D-glucose (left) and D-fructose (right).
Grain products: rich sources of carbohydrates
Glucose tablets

Polysaccharides serve as an energy store (e.g. starch and glycogen) and as structural components (e.g. cellulose in plants and chitin in arthropods).

3D structure of cellulose, a beta-glucan polysaccharide

Polysaccharide

Polysaccharides, or polycarbohydrates, are the most abundant carbohydrates found in food.

Polysaccharides, or polycarbohydrates, are the most abundant carbohydrates found in food.

3D structure of cellulose, a beta-glucan polysaccharide
Amylose is a linear polymer of glucose mainly linked with α(1→4) bonds. It can be made of several thousands of glucose units. It is one of the two components of starch, the other being amylopectin.
Some important natural structural polysaccharides
Schematic 2-D cross-sectional view of glycogen. A core protein of glycogenin is surrounded by branches of glucose units. The entire globular granule may contain approximately 30,000 glucose units.<ref>{{cite book | url = https://books.google.com/books?id=SRptlOx7yj4C | page = 12 | title = Exercise physiology: energy, nutrition, and human performance | vauthors = McArdle WD, Katch FI, Katch VL | edition = 6th | publisher = Lippincott Williams & Wilkins | date = 2006 | isbn = 978-0-7817-4990-9 }}</ref>
A view of the atomic structure of a single branched strand of glucose units in a glycogen molecule.

Examples include storage polysaccharides such as starch, glycogen and galactogen and structural polysaccharides such as cellulose and chitin.

Mutarotation: -glucose molecules exist as cyclic hemiacetals that are epimeric (= diastereomeric) to each other. The epimeric ratio α:β is 36:64. In the α-D-glucopyranose (left), the blue-labelled hydroxy group is in the axial position at the anomeric centre, whereas in the β-D-glucopyranose (right) the blue-labelled hydroxy group is in equatorial position at the anomeric centre.

Glucose

Simple sugar with the molecular formula C6H12O6.

Simple sugar with the molecular formula C6H12O6.

Mutarotation: -glucose molecules exist as cyclic hemiacetals that are epimeric (= diastereomeric) to each other. The epimeric ratio α:β is 36:64. In the α-D-glucopyranose (left), the blue-labelled hydroxy group is in the axial position at the anomeric centre, whereas in the β-D-glucopyranose (right) the blue-labelled hydroxy group is in equatorial position at the anomeric centre.
Glucose can exist in both a straight-chain and ring form.
Widely proposed arrow-pushing mechanism for acid-catalyzed dynamic equilibrium between the α- and β- anomers of D-glucopyranose
Glucose-Fructose-Mannose-isomerisation
Glucose metabolism and various forms of it in the process.Glucose-containing compounds and isomeric forms are digested and taken up by the body in the intestines, including starch, glycogen, disaccharides and monosaccharides.Glucose is stored in mainly the liver and muscles as glycogen. It is distributed and used in tissues as free glucose.
Diagram showing the possible intermediates in glucose degradation; Metabolic pathways orange: glycolysis, green: Entner-Doudoroff pathway, phosphorylating, yellow: Entner-Doudoroff pathway, non-phosphorylating
Glucose, 5% solution for infusions
Glucose tablets
Relative sweetness of various sugars in comparison with sucrose

Glucose for metabolism is stored as a polymer, in plants mainly as starch and amylopectin, and in animals as glycogen.

The human liver is located in the upper right abdomen

Liver

Major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth.

Major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth.

The human liver is located in the upper right abdomen
The liver, viewed from above, showing the left and right lobes separated by the falciform ligament
The liver, viewed from below, surface showing four lobes and the impressions
Impressions of the liver
Cells, ducts, and blood vessels
Hilum of the liver, circled in yellow
Shape of human liver in animation, with eight Couinaud segments labelled
CT scan showing an adult liver in the axial plane.
Adult ultrasound showing the right lobe of the liver and right kidney.
Biliary tract
Left lobe liver tumor
After resection of left lobe liver tumor
Maksalaatikko, a Finnish liver casserole
19th century drinking scene in Kordofan, home to the Humr tribe, who made a drink from giraffe liver. Plate from Le Désert et le Soudan by Stanislas d'Escayrac de Lauture.
Sheep's liver
Microscopic anatomy of the liver
Types of capillaries–sinusoid on right
alt=3D Medical Animation Still Shot Depicting parts of liver|3D Medical Animation Still Shot Depicting parts of liver
thumb|left|Liver veins
thumb|right|Diagram of liver, lobule, and portal tract and their inter-relations
Axial CT image showing anomalous hepatic veins coursing on the subcapsular anterior surface of the liver.<ref name="Sheporaitis">{{cite journal|pmid=9843288|year=1998|last1=Sheporaitis|first1=L|last2=Freeny|first2=PC|title=Hepatic and portal surface veins: A new anatomic variant revealed during abdominal CT|volume=171|issue=6|pages=1559–1564|doi=10.2214/ajr.171.6.9843288|journal=AJR. American Journal of Roentgenology}}</ref>
Maximum intensity projection (MIP) CT image as viewed anteriorly showing the anomalous hepatic veins coursing on the anterior surface of the liver
Lateral MIP view in the same patient
A CT scan in which the liver and portal vein are shown.
MDCT image. Arterial anatomy contraindicated for liver donation
MDCT image. Portal venous anatomy contraindicated for liver donation
MDCT image. 3D image created by MDCT can clearly visualize the liver, measure the liver volume, and plan the dissection plane to facilitate the liver transplantation procedure.
Phase contrast CT image. Contrast is perfusing the right liver but not the left due to a left portal vein thrombus.

Its other roles in metabolism include the regulation of glycogen storage, decomposition of red blood cells, and the production of hormones.