Biochemistry Flashcards
Definition of glycogenesis
- synthesis of glycogen from glucose
Define glycogenolysis
- breakdown of glycogen to form glucose
Define gluconeogenesis
- new synthesis of glucose from metabolic precursors
What is the main storage form of glucose in liver and muscle cells?
- glycogen
Glycogen is a ______
monosaccharide or polysaccharide?
- polysaccharide
what is the purpose of liver glycogen?
- broken down between meals and released to maintain blood glucose levels for red blood cells and brain
what is the purpose of muscle glycogen?
- provides energy via glycolysis and the TCA during bursts of physical activity
what carbons are linked between glucose molecules in glycogen?
- a 1-4 glycosidic links
- branches by a 1-6 glycosidic links
*** exam
What is required to add glucose to an existing glycogen chain?
- a glycogen primer [at least 4 glucose residues]
What is the name of the protein a glycogen primer binds to?
- glycogenin
What is the enzyme that converts glucose-1-phosphate to UDP-glucose?
- UDP - glucose pyrophosphorylase
Name of enzyme that converts UDP-glucose to glycogen?
- glycogen synthase
What is UDP - glucose?
- activated intermediates
- activated form of glucose
What is the role of glycogen synthase?
- synthesis of glycogen from UDP-glucose
- adds 1 glucose molecule to glycogen at a time
- rate limiting enzyme
What is the name of the enzyme that adds a branch to the 1-6 glycosidic branch in glycogen?
- transglycosylase
What is glycogenolysis catalysed by?
- glycogen phosphorylase
What are 3 precursors that can be used to generate glucose in gluconeogenesis?
- lactate
- amino acids
- glycerol
Gluconeogenesis is essentially the reverse of glycolysis
True or False
FALSE
- if it was simply in reverse you would need to overcome chemically challenging energy steps
- it employs 3 unique enzymes to over come these barriers
What is the last intermediate in the TCA (4 carbon?)
- oxaloacetate
How many liver enzymes are required in gluconeogenesis?
- 3 enzymes
What is the role of PEP CK
PEP carboxykinase
rate limiting gluconeogenesis
What is the cori cycle?
- process of recovering lactate that is generated in the skeletal muscle
- converted back to glucose, through the gluconeogenesis pathway
2 functions of insulin
- burns of glucose –> glycolysis
- activates glycogen synthesis
what are fats important for?
- as an energy source
- essential fatty acids
- for fat-soluble vitamins
What are the 3 different lipid compounds?
- simple lipids
- compound lipids
- steroids
What is the structure of a triglycerides?
- glycerol and 3 fatty acids
Fatty acids are mainly bent structures
true/false?
- FALSE
- mainly straight chains
What is a cis group?
- the 2 R groups are on the same side of the double bond
- cis –> think sisters (same side)
What are the 3 main products of fat digestion?
- glycerol
- fatty acids
- monoglycerides
What are chylomicrons?
- transport lipids absorbed from the intestine to adipose
Define lipolysis?
- breakdown of lipids
- by hormone sensitive lipases
Where is fat stored?
- in adipose tissue
Fatty acids are converted to ________ in the cytoplasm
- fatty acids oxidised to generate energy
- they are converted into CoA derivatives
Name a rate limiting step for the process of energy conversion of lipids to be metabolised
- carnitine shuttle
What is the carnitine shuttle?
- acyl- CoA transferred to carnitine
- facilitates acyl-CoA transport into the mitochondrial matrix
What is a rate limiting precursor for the TCA?
- Acetyl CoA
What is the end product of beta oxidation?
- Acetyl CoA
Where are ketone bodies formed?
- liver mitochondria
When does the formation of ketone bodies usually occur?
- in starvation and diabetes
How many cycles of oxidation is involved in beta oxidation for an even saturated fat?
(C2n)
n-1 oxidation occurs for complete catalysis
Malonyl CoA?
- precursor of the synthesis of fatty acids
- lipid anabolism
Define lipogenesis?
- fatty acid synthesis
- occurs mainly in the liver
- mainly takes place during excess energy intake
Where is Acetyl-CoA generated?
- in the mitochondria
What makes Acetyl-CoA, what enzyme?
- pyruvate dehydrogenase complex
Fatty acid synthase job?
- catalyses synthesis of saturated long-chain fatty acids from malonyl-CoA, acetyl-CoA and NADPH
4 Steps of fatty acid synthesis?
- condensation
- reduction
- dehydration
- reduction and release
What carries the synthesised lipid after it is made?
- acyl-carrier protein (ACP)
What does insulin signal?
- fed state
- stimulates storage of fuels and synthesis of proteins
What does glucagon signal?
- starved state
What does epinephrine signal?
- requirement for energy
- mobilise glycogen
Where are the glycerols for triglycerides synthesised?
- liver
- adipose tissue
What is a major site of amino acid degradation?
- liver
What is protein turnover?
- tightly regulated
- different rates
- damaged proteins have to be removed
Nitrogen containing excretory molecules?
- urea
- uric acid
- creatinine
- ammonium ion
Where is urea formed?
- the liver
What happens to glutamic acid during the formation of urea?
- de-amination
What are aminotransferases involved in?
- moving the amino group from the a-amino acids to a a-keto acid
- transamination
Where does deamination/urea cycle occur?
- in the liver
What occurs during deamination?
- amino group of glutamate is converted to free ammonium ion
What is an end product of the urea cycle?
- fumarate
- end-product in the cytosol
3 different inherited disorders of amino acid degradation
- alcaptonuria
- maple syrup urine disease
- phenylketonuria
