Mechanisms of Cell Injury

Question 1

List the general classifications of cell injury

Answer 1

Degenerative changes Growth Disturbances Circulatory disturbances Inflammation Neoplasia

Question 2

What do you need to know to understand the mechanisms of cell injury?

Answer 2

Structure of individual cells and their components Function of specific cells and their components

Question 3

Biological Function of Cell Membranes

Answer 3

Selective Barriers. First Point of contact with injurious agents Provide structural base of the enzymes and receptors essential to cell function

Question 4

Functions of the transmembrane proteins

Answer 4

Part of the structure Transport Enzymatic

Question 5

The Cellular Response and consequences to injurious stimuli will depend on:

Answer 5

Type of Injury Duration of the injurious agent’s effect Severity, extent of injury, concentration in tissue Type of cell injured and its current status [nutritional, hormonal, metabolic, oxygen requirement]

Question 6

Cell injury occurs when…

Answer 6

A cell can no longer maintain a steady state

Question 7

What does the “point of no return” refer to?

Answer 7

When the injury reaches a certain limit, whereby the cell cannot recover. [irreversible cell injury]

Question 8

Which cells are more sensitive to hypoxia and ischemia?

Answer 8

Brain and Heart Cells

Question 9

Which cells are more susceptible to injury by drugs and chemical

Answer 9

Liver Cells

Question 10

List 6 intracellular systems particulary vulnerable to injury

Answer 10

Cell membrane (plasma membrane and organelle membrane integrity) Aerobic respiration {mitochondrial oxidative phosphorylation/ATP production] Protein synthesis of structural and functional proteins Cytoskeleton: structural proteins for cell shape and movement Genetic apparatus: DNA

Question 11

Biochemical Mechanisms of Cell Injury (6)

Answer 11

1. ATP depletion 2. Mitochondrial damage 3. Intracellular calcium and loss of calcium homeostasis 4. Free radical induced injury (Oxidative Stress) 5. Defects in the membrane permeability 6. DNA damage

Question 12

ATP depletion and decrease in ATP synthesis are common consequences of what?

Answer 12

Ischemic and toxic injury

Question 13

What is ATP required for in the cell?

Answer 13

Membrane transport (Na+/K+ and Ca2+ pumps) Osmotic balance Protein Synthesis Protein Stability (proper folding) Lipogenesis

Question 14

Effects of depletion of ATP to <5%-10%

Answer 14

Sodium pump activity Increased activity of cellular enzymes Calcium pump Disruption of protein synthesis Cells deprived of energy source (oxygen, glucose)n

Question 15

During decrease O2 (ischemia) cellular energy metabolism is altered causing what?

Answer 15

Oxidative Phorphorylation to cease ►Decrease in ATP►Increase in anaerobic glycolysis►increase activity cell enzymes►clumping of nuclear chromatin

Question 16

What happens to cell proteins deprived of O2?

Answer 16

May become misfolded

• May cause cell injury or cell death

Question 17

When are misfolded proteins seen in cells?

Answer 17

Most common in cells exposed to stress (heat and free radicals)

Question 18

Mitochondria are damaged directly by_______

or indirectly by______________

Answer 18

Mitochondria are damaged directly by cerain toxins or indirectly by increased cytosolic Ca2+, free radicals, phospholipases, etc.