Carbohydrates Flashcards
How are disaccharides joined?
Aceytly (glycosidic) bond
Monosaccharides: What does an aldehyde and ketone make?
Aldehyde = aldose = hemiacetal
Ketone = ketose = hemiketal
Monosaccharides: how do you know if the sugar is D or L?
D = highest chiral C - OH is on right
L = OH is on left
Polysaccharides: What are the polysacharides in plants and animals and give a characteristic?
Plants = starch (amylose - no branching, amylopectin - branching at a–6)
Animal tissue = glycogen (branching)
More branching = better for energy.
What is dietary fiber?
Structural part of plants.
Soluble vs insoluble fiber
Insoluble - remain intact through intestinal tract and doesn’t dissolve in water which decreases constipation
Soluble - forms a gel that does dissolve in water which increases satiety and decreases cardiovascular disease risk by lowering blood cholesterol and type 2 diabetes.
Carb digestion: the mouth
a amylase breaks down a-1,4 glycosidic bonds (cellulose and lactose are resistant)
Carb digestion: stomach
a amylase is deactivated by low pH
Carb digestion: SI
a amylase (pancreas) are active at a neutral pH
Carb digestion: SI - BBE, list the 4 and what they do.
- a dextrinase: isomaltose –> 2 glucose
- maltase: maltose –> 2 glucose
- Invertase: sucrose –> glucose + fructose
- Lactase: lactose –> glucose + galactose
What is lactose intolerance?
lactose –> bacteria fermentation
How are monosaccharides absorbed?
Through enterocytes.
How is glucose absorbed?
Small amounts leak back out into the lumen from the enterocyte, small amounts diffuse into blood through basal membrane, but majority is trasnported into blood bly GLUT2. This is dependent on NA-K ATPase activity (glucose and galactose). To get sodium required for NaK ATPase, SGLT1 cotransports glucose and 2Na+. Fructose is brought into apical by facilitated transport and therefore, glucose, galactose and fructose all enter the blood via basolateral GLUT2.
What is the primary source of energy in the body and prevents ketosis?
Glucose
What are the three fates of glucose?
Glycogenesis for energy storage (forming glycogen)
Glycolysis for energy production
Hexose monophosphate shunt to generate precursors for biogenesis.
Glycogenesis - what does insulin do?
Insulin activates glycogen synthase, hexokinase in the muscle and glucokinase in the liver.
Glycolysis - what is the committed step and what are the 3 cycles glucose can go?
Phosphofructokinase is the first irreversible committed step which and then the glucose can either go to krebs (aerobic), lactic acid (anaerobic - 2 ATP produced), or Cori cycle (anaerobic - 2 molecule of lactate formed = 6 ATP consumed).
Glycolysis - pyruvate dehydrogenase
what is it? how many nadh produced?
gatekeeper to the krebs cycle
2NADH produced because must cycle twice for 1 molecule of glucose = 6ATP
Glycolysis - krebs cycle
how many Atp produced here?
3NADH + 1FADH2 + 1 GTP = 9 + 2 + 1 = 12 ATP x 2 cycles per one molecule = 24ATP
What are the conversion rates for nadh, fadh2 and gtp?
1NADH = 3 ATP
1FADH2 = 2 ATP
1 GTP = 1 ATP
therefore how many aTP formed from one glucose?
glycolysis = 8 ATP
pyruvate dehydrogenase = 6 ATP
Krebs cycle = 24ATP
Total = 38 ATP
What does the hexose monophosphate shunt produce?
NADPH
What is gluconeogenesis?
for when glucose is needed by the body (starvation), happens in the liver because muscle and adipose tissue lack the enzyme needed = glucose 6 monophosphatase, fructose 1-6 bisphosphatase, pyruvate carboxylase, phosphoenol pyruvate carboxykinase.
