Mitochondrial Transport / Brown Adipose Tissue (BAT) Flashcards
Explain transport across the inner mitochondrial membrane
Mitochondria are organelles, where most of ATP is produced
From oxidation of NADH (oxidative phosphorylation)
Some NADH is produced in glycolysis (in the cytoplasm)
Citric acid cycle/Krebs cycle = (further oxidation of pyruvate) takes place in mitochondria
Name the proteins the mitochondria transports
Phosphate
Pyruvate
ATP
Explain what shuttles are
Transport systems in the mitochondria that involve biochemical reactions and protein transports for NADH
Name and explain the protein transporter in the mitochondria that transports ATP and ADP
ATP-ADP translocase
Constitutes 15% oft the proteins in the inner membrane
An antiporter
Means of movements of ADP and ATP across the inner membrane
Exchange of ADP with ATP
Driven by positive membrane potential
Needs energy
Explain the glyerol-3-phospahte shuttle in the mitochondria
Transfers NADH to the electron transport chain (in the from of QH2)
Regenerates NAD+ (for re-use in glycolysis)
Important in muscle cells (with anaerobic processes)
Transfer of electrons to dihydroxyacetone-phosphate to make glycerol-3-phospahte
Electrons passed from glycerol-3-phospate to FAD to make FADH2
FADH2 then passes them to CoQ
Explain the malate-aspartate shuttle
Important in the heat and liver
2 membrane transports and 4 enzymes
Electrons transferred to oxaloacetate to make malate
Malate crosses membrane via transporter in exchange for alpha ketoglutarate (antiporter)
NADH reformed regenerating oxaloacetate
Oxaloacetate converted to aspartate by transmission with glutamate
Aspartate crosses membrane in exchange for glutamate
Aspartate deaminated to oxaloacetate
Explain transport through the inner mitochondrial membrane
ADP is transported into the mitochondria via the ATP/ADP translocase (an antiporter)
In muscle cytosolic NADH is transferred to the respiratory chain via the glycerol-3-phosphate shuttle (eventually QH2 is formed)
In the heart and liver cells the malate-aspartate shuttle leads to a transfer of NADH into the mitochondria
What are uncouplers?
They dissipate the proton gradient inside the mitochondria
Explain the role of natural uncouplers
Non-shivering thermogenesis
Generation of heat by uncoupling of oxidative phosphorylation
Explain the place where natural uncouplers are important in and how they occur
Important in:
Hibernating animals
New-borns
Mammals adapted to cold
Occurs via brown adipose tissue (BAT)
Explain brown adipose tissue (BAT) in the mitochondria
Rich in the mitochondria
Uncoupling protein (UCP-1 or thermogenic) in inner membrane forms a channel for protons
Explain how brown adipose tissue is increases and decreased in the mitochondria
Increased:
Fatty acid breakdown
Ketogenesis
Gluconeogenesis (synthesis of glucose)
Decreased:
Glycolysis
Biosynthesis
Explain the role of brown adipose tissue (BAT)
Hormones stimulate lipolysis
Free fatty acid activate UCP-1
Dissipate the proton gradient
ATP not synthesised and energy released as heat
Four other uncoupling proteins (UCP 2-5) which may have role in weight regulation
Explain hormonal control of BAT
Catecholamines: adrenaline and noradrenaline (epinephrine and norepinephrine)
Stimulate hormone sensitive lipase
Increase synthesis of uncoupling protein
Thyroid hormones: T3 and T4
Increase synthesis of uncoupling protein
What do the following stand for?
cAMP
PKA
HSL
FFA
UCP
T3, T4
DIO2
cAMP = cyclic AMP
PKA = Protein Kinase A
HSL = Hormone Sensitive Lipase
FFA = Free Fatty Acids
UCP = Uncoupling protein
T3, T4 = thyroid hormones
DIO2 = type 2 de-iodinease
