Lect. 3 Carbohydrates Flashcards
Glucose
Used in polymer synthesis
(monosaccharide)
Fructose
Component of table sugar
(monosaccharide)
Galactose
Component of milk sugar
(monosaccharide)
Ribose (Type)
Used in RNA nucleotides
Component of RNA
Deoxyribose (Type)
Used in DNA nucleotides
Component of DNA
Sucrose
In plants, table sugar
di-saccharide
glu + fru
Lactose
Milk sugar
di-saccharide
glu + gal
Maltose
Brewing sugar
di-saccharide
glu + glu
Starch
Storage in plants
polysaccharide
Glycogen
Storage in animals
polysaccharide
Cellulose
Structural in plants
polysaccharide
Chitin
Structural in animals in fungi
polysaccharide
Peptidoglycan
Structural in bateria
polysaccharide
2 types of sugar
aldoses and ketoses
difference lies in the location of the carbonyl gr. (-C=O)
Monosaccharide molecular formulas
multiple of CH2O
(1:2:1 ratio)
[CH2O]n where n is a nber between 3 and 7
3 most common sugars
- Trioses (smallest sugars)
- Pentoses (in DNA)
- Hexoses (common sugars)
3 common monosaccharides
(all hexoses)
- glucose
- galactose
- fructose
all 3 have chemical formula: C6H12O6
they are structural isomers of one another
most common monosaccharide
glucose
its open chain forms of glucose form ring structures in solutions
ring form is the most common form in living organisms
How does glucose form rings?
What is the ring called?
C1 aldehyde reacts with C5 hydroxyl gr. to form a ring called a pyranose ring
2 isomers of glucose ring structure
- α-glucose, OH gr. at C1 is on the opp. side of CH2OH
- β-glucose, OH gr. at C1 is on the same side as CH2OH
these isomeric forms differ in the orientation of the OH gr. at C1
Glucose in Biology
Glucose is the end product of what process? What is it used for?
- Photosynthesis in plants
- Glucose is used as an energy source in most organisms
During cellular respiration, cells oxidize glucose molecules converting the stored energy to a form that can be readily used for cell work.
Homeostasis of Blood Glucose
What regulates the concentration of glucose in the blood?
Where is it produced?
Hormones insulin and glucagon which are produced by the pancreas
transported thoughout the body via blood vessels
Almost all mechanism to maintain homeostasis:
negative feedback mechanisms
return a variable to its set point
loop: set point, stimulus -> detected by a sensor -> triggers response to return to the set point (effector)
What does insulin do?
Insulin decreases blood glucose.
Insulin can bind to receptors on surface of fat, muscle, and liver cells and promote the transport of glucose inside cells.
Glucose Transporter 4 triggered by insulin
Insulin decreases blood glucose levels by:
- Stimulating uptake of glucose in muscle
- Preventing breakdownof glycogen to glucose in the liver
- Stimulates adipose cells to store glucose as fat
What does glucagon do?
Glucagon increases blood glucose levels.
the pancreas is stimulated to secrete glucagon
Glucagon increases blood glucose levels by:
- Stimulating conversion of glycogen to glucose in the liver
- Breakdown of proteins into amino acids in muscle cells
- Breakdown of fats in adipose tissue and release of fatty acids
Sugars in food
Glucose is rarely found in its monosaccharide form in food. It’s often found as part of:
a disaccharide or starch
Sugars in Food
What is more commonly found in foods as it’s the primary sugar in foods such as fruits, vegetables, and honey?
Fructose
Disaccharides
How is a dissacharide formed?
A dissacharide is formed when a dehydration reaction joins 2 monosaccharides.
water is a product from the reaction
Lactose Intolerance
How is the digestion of disacharides and other carbs mediated?
It is mediated by enzymes synthesized by cells lining the small intestine.
Lactose Intolerance
What is Lactose Intolerance the result of?
A drop in lactase production
often following childhood
