All Important Things About Carbohydrate Metabolism - NEET PG Biochemistry
Feb 13, 2023
Carbohydrate metabolism is an important topic for the NEET PG exam because it is a fundamental aspect of human physiology and biochemistry. It plays a crucial role in the pathophysiology of various diseases such as diabetes, obesity, and metabolic syndrome. A deep understanding of the mechanisms involved in carbohydrate metabolism is essential for the diagnosis, treatment, and management of these conditions.
Additionally, the NEET PG exam is a comprehensive test that covers all aspects of medical science, and carbohydrate metabolism is a fundamental topic that is tested in biochemistry and endocrinology. Hence, a strong understanding of the topic is crucial for success in the NEET PG exam.
In this blog post, we’ll be covering important details pertaining to this topics. Read on.
Energy status of cell. If energy is present, TCA will not occur & vice-versa.
Availability of oxaloacetate. Thus, oxaloacetate is also regarded as carrier of TCA cycle or 1st Substrate of TCA cycle. Also, it plays a catalytic role in TCA cycle.
Only occurs in aerobic state
Not occurs in anaerobic state due to feedback regulation by NADH & FADH2 which are unable to enter ETC as O2 is absent.
4 Enzymes of Gluconeogenesis which are different from Glycolysis
Enzyme
Feature
Pyruvate carboxylase
Present in mitochondriauses ATPactivated by acetyl CoA
PEPCK (Phosphoenolpyruvate carboxykinase)
Both are present is cytoplasm
Fructose -1-6- Bisphosphatase
Glucose -6- phosphatase
present in endoplasmic reticulum (to prevent glucose-6-P breakdown to glucose)common enzyme of gluconeogenesis and GlycogenolysisPresent in liver but absent in muscles
Substrates of Gluconeogenesis
Pyruvate and Lactate
Glycerol and Propionic acid
Glycogenic amino acid
Both Glucogenic & Ketogenic amino acids
Any TCA intermediates
Reciprocal regulation of Glycolysis & Gluconeogenesis
GLYCOGEN
Stored mainly in liver & muscle and minor amount in brain
End-product of liver glycogenolysis is glucose.
Main purpose of liver glycogen is to maintain blood glucose
End-product of liver glycogenolysis is glucose-6-phosphate.
Main purpose of Muscle glycogen is to provide energy for muscle contraction.
Glycogen Synthesis
RLE for glycogenesis: Glycogen synthase
Glycogenolysis
Glycogenolysis enzymes
Glycogen Phosphorylase
RLE of glycogenolysis
Requires Vit B6
Breaks α (1-4) bond
Releases 90% of glucose in the form of glucose-I-PO4
Debranching enzyme
Breaks α (1-6) bond
Releases 10% of glucose in the form of D-glucose
HMP
Glucose 6–P (a hexose phosphate) is the starting material hence the name Hexose Monophosphate
Pathway
Other name is Pentose Phosphate Pathway (PPP) as Pentose Phosphate i.e. Ribose 5–P is synthesized only by this pathway.
Occurs in cytoplasm
Produces NADPH in phase-I of HMP (irreversible oxidative phase)
Produced Ribose-5-P in phase-II of HMP (reversible Non-oxidative phase)
It’s an anabolic pathway thus is activated by insulin
RLE: Glucose-6-P dehydrogenase (G6PD)
Site of HMP: Liver, lactating mammary glands, adipose tissue, placenta, gonads & RBC.
Tissues which are never site of HMP: Skin and Non-lactating mammary glands
Q. All are features of gluconeogenesis except?(JIPMER Dec 2019)
Gluconeogenesis is synthesis of glucose from non-carbohydrate source
Mainly takes place in liver
Seen in fasting state
Step are simple reversal of glycolysis
Q. Glucose is stored in Glycogen form, why? (AIIMS June 2020)
Compact
Can be reduced from multiple branches lends
Can be stored ale multiple Sites
Can provide glucose an muchas needed and when needed for 1 week
Q. Complex IV in Election Transport chain is inhibited by? (FMGE Dec 2020)
Cyanide
Barbiturates
Phenylnitrone
Malonate
Q. Enzymes used in gluconeogenesis are? (INICET Nov 2020)
Hexokinase
PEPCK
Pyruvate carboxylase
GLU-6 Phosphatase
Pyruvate kinase
Q. Enzyme present in both glycolysis and gluconeogenesis? (AIIMS June 2020)
PFK
PEP-CK
Phosphoglycerate kinase
Pyruvate kinase
Q. Cytochrome C oxidase is inhibited by all EXCEPT?(INICET July 2021)
Methane
H2S
CO
Cyanide
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