Carbohydrate Metabolism Flashcards
In what three ways can ATP be replenished?
Creatinine phosphate
Anaerobic metabolism
Aerobic metabolism
Give some examples of polysaccharides.
Starch
Cellulose
Name some disaccharides.
Maltose
Sucrose
Lactose
Name some monosaccharides.
Glucose
Fructose
What is the difference between D-glucose and L-glucose?
D-glucose rotates the plane of polarised light to the right.
L-glucose is the mirror image enantiomer of this and is not found naturally.
What constitutes whether a glucose molecule is alpha or beta?
Alpha-glucose refers to the -OH being below the first carbon atom.
Beta-glucose is the -OH being above the first carbon atom
What is the glycosidic bond found in starch?
Alpha-1,4- glycosidic bond
What breaks down starch into glucose, maltose and dextrins?
Salivary amylase
What breaks down dextrins into more disaccharides?
Pancreatic amylase
What brush border enzymes break down maltose, sucrose and lactose respectively?
Maltase breaks down maltose into glucose
Lactase breaks down lactose into glucose and galactose
Sucrose breaks down sucrose into glucose and fructose
Which starches are slowly digested and why?
- trapped inside intact starch granules/plant cell wall structure
- resistant to amylase as 3D structure is too tightly packed
- associated with dietry fibre, which slows the absorption and digestion by making the gut contents viscous
- CHO food containing high levels of fat
How do humans process cellulose?
We can’t because we don’t have the enzymes to break down the beta-1,4 links in cellulose
SGLUT-1 transporters are found where and have what characteristics?
Found on the intestinal mucosa and kidney tubules.
Cotransports one molecule of glucose or galactose along with two sodium ions. NO FRUCTOSE
GLUT-1 transporters are found where and have what characteristics?
It’s found on all cells
It transports glucose (high affinity) and galactose.
NO FRUCTOSE
GLUT-2 transporters are found where and have what characteristics?
These are found on liver and pancreatic beta cells
Transports glucose, galactose and fructose. A low affinity, high capacity glucose transporter.
GLUT-3 transporters are found where and have what characteristics?
Found in the placenta, brain and testes.
Transports glucose (high affinity) and galactose, and is the primary glucose transporter for neurons.
NO FRUCTOSE
GLUT-4 transporters are found where and have what characteristics?
It’s found on skeletal muscle, cardiac muscle and adipose tissue
It’s the insulin-responsive glucose transporter with a high affinity for glucose
GLUT-5 transporters are found where and have what characteristics?
Found in small intestine and sperm
Transports fructose, but not glucose or galactose
Give some ways glucose can enter the bloodstream.
From the diet, glycogen stores in the liver and gluconeogensis by the liver.
Give some ways glucose can be removed from the blood.
It can be taken up by tissues, turned into glycogen in the liver, turned into glycogen in the muscle, be used to synthesis FAs and triglycerides and be used to synthesis pentoses.
What can happen to glucose once it enters a cell
Produce ATP, be stored as glycogen, be stored as a lipid, be made into pentoses and be made into glycolipids/glycoproteins.
What is done to all glucose molecules in every possible pathways within a cell?
There is phosphorylation of the glucose into glucose-6-phosphate
What is the physiological function of immediately phosphorylating glucose to G6P?
It prevents the glucose from being transported out, trapping it within the cell.
What catalyses the glucose to G6P phosphorylation reaction?
Hexokinases I-IV, depending on the tissue type.
