Energy Production-carbs Flashcards
What is Acetylco-enzyme A?
A carrier that feeds into the KRebb cycle
Describe the first stage of catabolism
Conversion of nutrients to a form that can be taken up by cells
It’s extracellular (in the GI tract)
It turns complex molecules into building blocks
These blocks are absorbed into the blood stream
No energy release at this stage
Describe the second step of catabolism.
Intracellular (cytoplasm and mitochondria)
The many building block molecules form few simple molecules
It’s oxidative and requires reducible coenzymes NAD
Some ATP energy is produced
Describe the 3rd stage of catabolism
Takes place in mitochondria Krebbs (tricarboxylic acid) Cucle Oxidative (needs NAD and FAD) Some ATP energy directly produced Acetyl turns to 2 CO2’s
It also produces precursors to biosynthesis
Describe the 4th stage of catabolism
Takes place in mitochondria Electron transport and ATP synth NADH and FAD2H re-oxidised O2 needed (turns to H2O) Large amounts of ATP produced
What is the general formula of a carbohydrates
(CH2O)n
Can contain aldehyde or keto groups
List the min 3 dietary monosaccharides
Glucose
Fructose
Galactose
What cells have an absolute tissue requirement and why?
Red blood cells
Neutrophils
Innermost cell of kidneys medulla
Lens of the eye
No mitochondria so cant metabolise glucose
Their uptake depends directly on blood glucose
Describe the metabolism pathway of carbohydrates from when they enter the body
Saliva-amylase
Stomach acid-kills enzymes +churning
Pancreas-amylase
Small intestine-disaccharidases attached to brush border membrane
Why isn’t cellulose broken down by humans?
The beta glycosidic linkages are different to the alpha bands of starch so cant be digested
Describe the criteria for primary lactase deficiency
An absence of lactase persistence allele
High prevalence in northwest Europe
Adults only
Describe the criteria for secondary lactase deficiency
Caused by injury to small intestine (gastroenteritis, coeliacs, Chron’s, ulcerative colitis)
Occurs in adults and infants
Generally reversible as once underlying cause treated lactase production begins again
Describe the criteria for congenital lactase deficiency
Extremely rare
Autosomal recessive defect in lactase gene
Cannot digest breast milk
Must be given alternatives
List some symptoms of any lactose intolerance
Bloating Cramps Flatulence Diarrhoea Vomiting Loud rumbling stomach
Hw are sugars absorbed into the blood from the SI
Active transport (sodium potassium pump) Passive transport (via GLUT2) Blood transport to tissues Facilitated diffusion ( transport proteins into target cells)
What are the functions of glycolysis?
Oxidise glucose
Produce NADH
Synthesise ATP from ADP
Produce C6 and C3 intermediates (Pyrvate)
What are the features of glycolysis?
Central pathway of CHO catabolism Occurs in all tissues (cytoplasm) Exergonic and reductive C6 goes to 2C3 (no CO2 loss) Only pathway that can work anaerobicly (when LDH added) Irreversible
Name the 3 enzymes in glycolysis that can have control exerted over them.
Hexokinase (glucokinase in liver)
Phosphofructokinase-1
Pyruvate kinase
Why does glycolysis have so many steps?
Chemistry is easier in smaller stages
More efficient energy conversions
Gives versatility (interconnections with other pathways, intermediate products, parts are reversible)
Allows for finer control
What steps in glycolysis are irreversible and why?
Step one and three due to their large negative change in energy. It’s an investment in ATP so is a waste if reversible.
Step 3 is the committing step its the first step that commits glucose to metabolism via glycolysis
How can glycolysis be used in clinical situations?
Cancer cells have up to 200 times greater glycolysis rate
If give patient radioactive hexokinase substrate its taken up by metabolising cells and gets stuck in the tissues due to its negative charge. The radioactivity can be seen on imaging so shows in cells with sig higher rate
