Mitochondria, Peroxisomes, and Lysosomes
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- What is the main function of mitochondria?
- To convert chemical fuels into energy forms that drive cell reactions
- What are other functions of the mitochondria
- Steps in steroid synthesis
- Where is the mitochondria located?
-
in all mature eukaryotic cells exc. RBC's
Found where metabolic act. is high - What is a porin?
- A protein that forms a freely permeable to small ions channel
- What molecule(s) is the inner membrane rich in?
- Cardiolipin, pump and transport systems
- What part of the metabolic pathway does the inner membrane participate in?
- the ETS
- Where is the ADP->ATP phosphorylating system located?
- Seen as elementary particles on stalks from the inner surface of the inner membrane?
- What is the function of cristae?
- increase surface area
- When will a cell have more cristae than another?
- When that cell has a larger energy requirement than the other.
- Cells ass. w/ steroid synthesis tend to have ________ shaped cristae?
- tubular
- The mitochondrial matrix is electron _____, whereas the innermembrane space is electron _______
- dense; lucent
- The intermembrane space is similar in concentration to the _______
- cytosol
- What enzymes are located in the innermembrane space?
- Creatine kinase, adenylate kinase, cytochrome C (ATP-using enzymes)
- What important cellular components are present in the matrix of the mitochondria
-
1.Kreb's Cycle enzymes
2.B-oxidation enzymes
3.closed-circle double-stranded mitochondrial DNA
4.rRNA, tRNA, mRNA - Mitochondria are more numerous in cells using _______________?
- Large amounts of energy
- How does the elongation of FA's occur in the mitochondria?
- by addition of acetyl-CoA
- What are most mitochondrial proteins coded by?
- nuclear DNA, synth. in cytosol, trans. to mito. using E-req. process
- Where types of cells tend to have more mitochondria?
-
1.The myofibrils of skeletal and cardiac muscle
2.Basal/lateral surfaces of cells inv. in pumping ions
3.Spermatozoa
4.Axon Terminal - How do mitochondria grow?
- By the addition of new materials produced in the cytoplasm to existing mito. components
- How do proteins destined for the mitochondria get there?
- A signal peptide sequence is recognized by a receptor
- Where is the receptor located?
- Outer mitochondrial membrane
- What does the receptor do to get the precursor protein inside?
- Crosses both membranes at a contact site
- What happens after crossing?
- Signal sequence is cleaved
- How do mito. proliferate?
- Organelle division (fission), not in-step with the cell cycle.
- Is the mito. capable of protein synth.
- a little
- What does mito. DNA code for?
-
13 TCA Enzymes
2 rRNA's
22 tRNA's - What is the hypothesis of how mitochondria originated in cells?
- When the [02] increased, primitive eukaryotic cells ingulfed aerobic bacteria via endocytosis and lived in symbiosis w/the bacteria
- What three diseases are being ass. w/mitochondrial dysfunction and where is it inherited from?
-
Age-related diseases
1.Alzheimer's
2.Heart Disease
3.Schizophrenia
*Inherited from mother - What other organelle do peroxisomes usually ass. with?
- Smooth ER
- Where are large peroxisomes present?
- liver
- What type of peroxisomes are found in the rest of the body?
- micro-peroxisomes
- Do peroxisomes contain DNA or RNA?
- NO
- Where are peroxisomal enzymes produced?
- In the cytosol
- What directs peroxisomal proteins to the membrane?
- Signal sequence
- How do peroxisomes divide?
- fission
- What do perox's do to very-long chain fatty acids?
- Break down into acetyl-CoA via B-oxidation
- What inclusion is commonly found in other animals peroxisomes but not humans?
- urate oxidase
- What are the functions of perox's?
-
1.Oxidze specific organic substrates
2.Segrete enzymes that use H202
3.Aids bile acid synthesis (via action of perox. enzy's)
4.B-oxidation of Very long chain FA's - What is the byproduct of oxidase action?
- H202
- How is H202 destroyed?
- By catalase
- What causes Zelwegger Syndrome?
- The failure of peroxisomal membrane transport proteins in bringing peroxisomal enzymes into the peroxisome.
- What are the classifications of Zelwegger's
-
G1: complete loss of f(x)=death
G2: only a few peroxisomal enzymes disabled
G3: only one enzyme disabled - What is adrenoleukodystrophy?
- The inability of peroxisomes to transport long-chain fatty acids into the cell, causes FA buildup: damages myelin, neurological damage
- What is the intracellular digestive system?
- Lysosomes and their ass. organelles
- Describe the maturation of a lysosome?
-
1.Early endosomes take up material via endocytosis (sorting occurs)
2.Merge w/ late endosomes (sorting occurs)
3.Late endosome matures into lysosome - What is unique about the inner lysosomal membrane?
- Highly glycosylated
- Why does this occur?
- prevents hydolases inside from digesting the lysosome's membrane
- What is a residual body?
- Old lysosomes containing indigestible material
- What is the optimal pH of lysosomes?
- 5
- What modifications occur to lysosomal enzymes in the Golgi
-
1.Addition of mannose-6-phophate (cis-golgi network)
2.Other carb mod's
3.Sorted
4.Packaged into a vesicle - What purpose does the sugar groups serve on lysosomal enzymes?
- Serves as a label for routing the enz's to the lysosome
- What are the methods used by lysosomes to digest material?
-
1.Endocytosis
2.Receptor-mediated endocytosis
3.Phagocytosis
4.Autophagy - What type of molecules enter via endocytosis?
- Fluid and small proteins
- What is clathrin-independent fluid phase pinocytosis?
- The forming of vesicles around fluid and into the lysosome
- What happens if that fluid must be digested?
- Sent to Early Endosomes
- How does receptor mediated endocytosis occur?
- By the binding of a ligand to a receptor on the lysosomal membrane.
- What does this binding cause?
- "Capping"(aggregation) of the receptor-ligand processes
- How are these aggregates now taken into the lysosomes?
- Via vesicles formed from the molecule clathrin.
- If to be digested what happens?
- The vesicle fuses with an early endosome
- Phagocytosis involves the uptake of ________
- large, solid materials (bacteria i.e.)
- What protein is used for phagocytosis?
- Actin
- What are the specific functions of lysosomes?
-
1.breakdown of worn-down or excess organelles
2.Digestion of materials
3.Thyroid Hormone secretion
4.Resorption of Bone (osteoclasts)
5.Provide nutrients during starvation