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Medical Genetics I > Mitochondrial Disorders Pt. 1 > Flashcards

Mitochondrial Disorders Pt. 1 Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

Define “metabolism”

A

How the body (all organs, all cells) functions by generating energy through intricate chemical steps from daily nutrition/food consumption.

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2
Q

Define “basal metabolic rate”

A

Minimum calories needed at rest for energy for overall cell/organ function. This includes functions such as:

  • Ion transport
  • Digestion
  • Brain activity
  • Gut movement
  • Breathing
  • Heart pumping

Percent of Basal Metabolic Rate: Muscle (20%), Liver (19%), Brain (17%), Digestion (10%), Heart (8%), Kidneys (7%), Fat (3%), rest is misc.

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3
Q

Name some things that impact your overall metabolic rate

A

Resting metabolic rate: warmth regulation, digestion, other processes
Daily activity: physical, mental
Demographics: gender, age, physique

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4
Q

What are the 4 components of food?

A

Fat, Carbs, Protein, Vitamins

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5
Q

What is the function of a vitamin?

A

Cofactor for crucial metabolic pathways

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6
Q

What is the normal pH that is essential for proper functions of all enzymes in the body?

A

7.4

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7
Q

Name a change from the norm (homeostasis) that can be life threatening

A

Acidosis (particularly lactic acidosis)

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8
Q

What is it called when protein breakdown happens during illness?

A

Catabolism

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9
Q

What is the main energy source for your cells?

A

Glucose

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10
Q

Blood glucose needs to be between ___ - ___ mg/dL for adequate function of organs (including the brain)

A

80-120 mg/dL

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11
Q

___ is how extra glucose is stored and also what is converted back into glucose when needed

A

Glycogen

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12
Q

Where are fatty acids absorbed?

A

Gut

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13
Q

Where are fatty acids processed?

A

Liver

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14
Q

where does energy metabolism occur?

A

Mitochondria

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15
Q

What are stored for energy once glucose/glycogen stores are depleted?

A

Fatty Acids

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16
Q

Fatty Acids are the main source of energy for what?

A

Muscle, including the heart

17
Q

Enzyme defects can be partial or complete. What determines the severity and onset of illness?

A

Residual or remaining enzyme activity

  • Mild –> teenage/adult presentation
  • Severe –> newborn
18
Q

What might you need to measure enzyme activity, since direct can be difficult?

A

Tissue Biopsy

19
Q

What does Mitochondrial Dysfunction result in?

A

Cell injury –> cell death –> organ failure

20
Q

What organs are most impacted by mitochondrial dysfunction?

A

Organs w/ high energy demand

  • Muscle (cardiac and skeletal)
  • Endocrine organs
  • Kidneys
  • Intestinal tract
  • Retina
  • CNS
21
Q

Define “mitochondrial disease”

A

Chronic disorders that occur when mitochondria in numerous cells fail to produce sufficient energy for adequate function w/ subsequent organ failure

22
Q

Mito diseases are the result of either ___ or ___ mutations in ___ or ___

A

inherited, spontaneous, mtDNA, nDNA

Note: these mutations lead to altered function of proteins or RNA inside the mitochondria

23
Q

Name 6 other major metabolic pathways that mitochondria are involved in

A
  • Purine/pyrimidine biosynthesis
  • Heme synthesis
  • Urea cycle
  • Cholesterol metabolism/hormone synthesis
  • Neurotransmitter metabolism
  • Free radical production and detoxification
24
Q

What are mitochondria prone to?

A

Environmental insults such as aging, drugs, etc.

25
Q

What is meant by “mitochondria are dynamic organelles”?

A

They divide, fuse, and migrate

26
Q

True or false: a single cell can contain both mutant/defective mitochondria and normal mitochondria

A

True

Note: this is why symptoms can be so variable b/w individuals in the same family. Ratios can also change over time and as we age, we all get mitochondrial damage

27
Q

What 6 things occur in cells w/ defective mitochondria?

A
  • No ATP
  • Backlog of unused fuel molecules and oxygen (free radicals toxic to cell)
  • Inadequate oxygen supply
  • Lactic acidosis damages muscle and nerve tissue
  • Reactive oxygen species
  • Vitamins/antioxidants target this issue to minimize tissue damage
28
Q

What is the ONLY way we can measure activity of the electron chain complexes (in the oxidative phosphorylation process/respiratory chain)?

A

Must use fresh or frozen muscle biopsy, fresh is optimal for evaluation

Note: only a few labs still do this testing since it’s mostly been replaces by genetic testing

29
Q

How many genes does it take to make a mitochondrion?

A

3000

30
Q

What is the only metabolic pathway under dual control of both the mtDNA and nDNA genomes?

A

Electron transport chain

31
Q

Regarding the genes that control the electron transport chain:
nDNA has ___ genes and has ___ inheritance pattern
vs.
mtDNA has ___ genes and has ___ inheritance pattern

A

850 genes, AR
vs.
13 genes, Mitochondrial inheritance through maternal circular DNA

32
Q

Describe mtDNA

A
  • closed, circular
  • maternally inherited
  • thousands of copies per cell
  • copy number is very dynamic
33
Q

What are 3 concepts that impact the effect of a mitochondrial disease on a person?

A
  • Heteroplasmy: presence of mixture of mutant and normal mtDNAs
  • Tissue distribution: which tissues have the mutant mtDNAs
  • Threshold effect: vulnerability of each tissue to impaired oxidative metabolism

Note: at cell division, mitochondria are distributed unequally and do not necessarily reflect the ratio found in the progenitor cell

Medical Genetics I (18 decks)

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