Carbohydrates and Sugars Flashcards
What is the definition of metabolism?
A sum of enzyme catalyzed reactions by which a living cell perpetuates and replicates itself.
Define intermediary / energy metabolism
Set of reaction concerned with generation or storing energy and using that energy for biosynthesis of small molecules. In other words it is associated with maintenance of cellular ATP & blood glucose levels.
Describe anabolic pathways
Biosynthesis pathways that use energy derived from catabolic pathways. Ex: Gluconeogenesis and glycogenesis
Describe Catabolic pathways
Oxidative breakdown of complex larger molecules that result in energy release captured by formation of ATP. This can be described as an exergonic process. Examples are glycogenolysis and glycolysis.
What is the term for a metabolic pathway that can be both catabolic and anabolic? What pathway would this be?
Amphibolic; Citric acid cycle
What can be accomplished removing H+ from a carbohydrate in a stepwise fashion? What other things are needed?
Energy release; enzymes, and electron/protein acceptors such as NAD+ or FAD+
NADPH or NADH loses a hydrogen this is an example of?
Oxidation
NAD+ or NADP+ gains a hydrogen this is an example of?
Reduction
Give two examples of proton / hydrogen acceptors.
NAD+ and NADP+
What are three monosaccharides?
fructose, galactose, and glucose
Name three disaccharides.
Sucrose, lactose, and maltose
What is the suffix in a name for sugars?
-ose
Monosaccharides are _______.
D - stereoisomers in humans.
What are the two different ring structures?
Pyranose - 6 carbon ring. Furanose - 5 carbon ring.
What group and which carbon / position can be adapted to be in alpha or beta conformation?
The OH - group at position one.
What conformation is most stable for glucose?
Beta conformation
What conformation is most stable for polysaccharides such as starch and glycogen?
Alpha conformation.
What is the term to describe a sugar that has 2 to 10 monosaccharides per unit?
Oligosaccharide
What is the term to describe a sugar that has greater than 10 monosaccharides per unit?
Polysaccharides such as cellulose, starch, glycogen, and glucan (polysaccharide of D - glucose monomers)
What sugar is responsible for 80% of monosaccharides in a person’s diet?
Starch (polysaccharide)
What minor carbs are in a person’s diet?
Glycogen, alcohol, lactic acid, pectin & dextran
Where does digestion start for sugars?
In the mouth where amylase is secreted. Amylase hydrolyzes starch into maltose and other small polymers of glucose.
What inhibits amylase activity as carbs make its way through the body?
Gastric secretions inhibit amylase activity after about an hour in digestion.
What is another source of amylase in the body?
Amylase is secreted from the pancreas when chyme enters the duodenum.
What needs to happen to disaccharides and oligosaccharides before they are absorbed?
They need to be broken down to monomers
What are the four enzymes located in brush border of cells?
Lactase, sucrase, maltase, & alpha - dextrinase.
Where do monosaccharides go after being absorbed?
To the portal blood
Which glucose transporter has a low affinity to glucose?
GLUT - 2 found in areas of high glucose concentration such as small intestines, renal tubules & liver.
If a glucose transporter has a high affinity to glucose would the Km value be high or low?
Low Km value
If the glucose transporter has a low affinity to glucose would the Km value be high or low?
High Km
Define Km for enzyme kinetics
The concentration of substrate which permits the enzyme to achieve half Vmax (reaction rate when the enzyme is fully saturated by substrate)
Which glucose transporter has a high affinity to glucose?
GLUT - 1 and GLUT - 3 in glucose sensitive tissue such as the brain and RBCs
Which glucose transporter has an intermediate affinity to glucose?
GLUT - 4 in insulin dependent muscle & adipose cells
What is the purpose of glycogen?
Storage form of glucose in muscles and liver. Another name for it is polymeric glucose
What is the purpose of monosaccharides?
Its the major source of energy and primary form of nutrition.
What kind of substance does the brain use to fuel brain activity?
Glucose
What can glucose be converted into besides energy for the body?
Ribose, or turned into oxidized / reduced form such as mannitol or glucuronic acid
What are the components of synovial fluid and connective tissue?
Long chains of hyaluronic acid and keratin sulfate.
How do monosaccharides turned into energy?
They are phosphorylated. Depending where the phosphate group is added will decide where they enter glycolysis pathway. Galactose is phosphorylated to G-1-P, Glucose is phosphorylated to G-6-P, and Fructose is phosphorylated to F-6-P or F-1-P.
Where is fructose primarily metabolized?
Liver, kidney, and small intestine
In the liver, what enzyme is responsible for adding a phosphate group to position one (1st carbon)?
Fructokinase
What enzyme is responsible for adding a phosphate group to the sixth position (6th carbon)?
Hexokinase, you get F-6-P
what is the disorder that describes the liver is deficient for fructokinase?
Essential fructosuria. Another name that describes it is false diabetes mellitus.
Fructose - 1 - P adolase is deficient in the liver, kidney cortex, and small intestine. What is this condition called?
Hereditary fructose intolerance
A patient has hereditary fructose - 1,6 - bisphosphatase deficiency is glycolysis affected?
No
What needs to happen for galactose to enter glycolysis?
Galactose needs to be phosphorylated by galactokinase to make Galactose - 1 - phosphate. Then Gal-1-P needs to be epimerized to Glucose-1-P by UDP-Glc-Gal-1-P uridylyltransferase. The last step before entering glycolysis is moving the phosphate group with the help of phosphoglucomutase.
The body is deficient in uridylyltransferase (GALT) what condition describes this disorder?
Classic galactosemia (leads to lactose intolerance)
A disorder that is due to the loss of galactokinase (GALK) and what are the consequences?
Galactosemia; lactose intolerant, and may lead to blindness and fatal liver damage.
What organ controls blood glucose levels?
The liver.
What ways does the liver have to increase glucose levels?
Draw on glycogen levels, convert intestinally absorbed galactose & fructose to glucose, and produce glucose through the gluconeogenesis pathway (G-6-phosphatase activity).
What organ produces important glucose metabolites and what are they?
Liver; Ribose & oxidizes / reduces to form complex monosaccharides
What is gluconeogenesis?
Process that produces glucose-6-phosphate from amino acids, fatty acids, glycerol, and lactate. Gluconeogenesis is an anabolic pathway that forms glucose from non-carbohydrate substances.
What is glycogenolysis?
a process by which glycogen is broken down into glucose.
What is glycolysis?
The catabolic pathway that breaks down monosaccharides to produce 2 pyruvate molecules, 2 ATP, and 2 NADH.
What is glyconeogenesis?
Produces the storage form of glucose. It occurs in the cytoplasm in liver and muscle cells.
What is the hexose monophosphate shunt?
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