Lecture 5: Life of a Cell

Question 1

Embryonic stem cell

Answer 1

ESC = true human stem cell, not found in adults

Question 2

Stem cell

Answer 2

Cell that can divide indefinitely, self-regenerate, and differentiate into specific cell types

Question 3

Progenitor cell

Answer 3

Cell that retains self-regeneration and some pluripotency; technically more differentiated than a true stem cell

Question 4

Precursor cell

Answer 4

Differentiating cell that is not able to self-regenerate

Question 5

Adult “stem” cells

Answer 5

Most pluripotent cell within a tissue.
-MSC: CT, muscle, adipose
-HSC: blood cells, some CT
-No stem cells for cardiac muscle
-Neural SCs
Spermato/oogonium: male/female germ line SCs
-Myosatellite cells

Question 6

Cell cycle phases

Answer 6

1. Gap-1 (G1)
2. S-phase (DNA replication)
3. Gap-2 (G2)
4. Prophase
5. Metaphase
6. Anaphase
7. Telophase

Question 7

Quiescent cells

Answer 7

Cells that have left the cell cycle (gap-0/G0 phase); aka terminally differentiated cells

Question 8

Chromosome

Answer 8

DNA strand; 2 homologous chromatids joined by a centromere

Question 9

Mitosis chromosome counting

Answer 9

2n1x (1 cell) -> 2n2x (1 cell) -> 2n1x (2 cells)

Question 10

Meiosis chromosome counting

Answer 10

2n1x (1 cell) -> 2n2x (1 cell) -> 1n2x (2 cells) -> 1n1x (4 cells)

Question 11

n, x system for chromatid counting counting

Answer 11

n = number of distinct chromatids (n = 23 in humans)
x = number of exact copies of each chromatid (x = 1 normally, x = 2 after DNA replication)

Question 12

Gamete development stages

Answer 12

1. Stem/progenitor cells (spermato-/oogonia)
2. Pre-meiosis I (primary spermato-/oocytes)
3. Pre-meiosis II (secondary spermato-/oocytes)
4. (Male) precursors (spermatids)
5. Adult cells: (spermatozoa, ova)

Question 13

Telomeres

Answer 13

Repetitive DNA sequences at chromosome ends that protect them from fraying. Telomeres shorten after each division.

Question 14

Types of cell death

Answer 14

1. Apoptosis
2. Necrosis/necroptosis
3. Autophagy
4. Senescence
5. NETosis
6. Many others (ferroptosis, pyroptosis, etc.)

Question 15

Apoptosis

Answer 15

Caspase-dependent cell suicide; orderly, non-immunogenic destruction

Question 16

Necrosis/necroptosis

Answer 16

Non-caspase dependent cell death pathway; results in extracellularization of DNA/RNA (immunogenic DAMPs)

Question 17

DAMPs/PAMPs

Answer 17

Damage/pathogen associated molecular patterns. Recognized by pattern recognition receptors (PRRs) to stimulate immune activity

Question 18

Autophagy

Answer 18

Compartmentalization and destruction of cytoplasm/organelles. Can rescue a stressed cell or lead to traditional cell death.

Question 19

Senescence

Answer 19

Exiting of cell cycle, leaves cell incapable of replication and creates secretome complex. Immortal cells escape senescence. Often caused by irreparable DNA damage; anti-tumor function.

Question 20

Secretome

Answer 20

Substances secreted by a senescent cell telling the immune system to kill and clean. Can induce inflammation and fibrosis.

Question 21

Types of tissue necrosis

Answer 21

1. Coagulative
2. Liquefactive
3. Caseous
4. Fat
5. Fibrinoid
6. Gangrenous

Question 22

Tissue necrosis by rate of chemical dissolution

Answer 22

Fast = liquefactive
Normal = caseous
Slow = coagulative

Question 23

Coagulative necrosis

Answer 23

Firm area due to acute blood loss to region. Cells are preserved due to limited macrophage activity

Question 24

Liquefactive necrosis

Answer 24

Fluid products, primarily caused by neutrophil response

Question 25

Caseous necrosis

Answer 25

"Cheese-like"; balanced macrophage, neutrophil, lymphocyte response; disease specific process e.g. TB

Question 26

Fat necrosis

Answer 26

Lipid dominated necrotic tissue; adipose necrosis

Question 27

Fibrinoid necrosis

Answer 27

Caused by immune response in blood; creates deposits similar to clots

Question 28

Gangrenous necrosis

Answer 28

Occurs when affected tissue is too large to be resolved by immune response or scarring, or if area is inaccessible to the immune system.

Question 29

Pus

Answer 29

Whitish fluid primarily made of cell debris from dying immune cells. Mechanically forces foreign material out of the tissue

Question 30

Differential stages of spermatogonia

Answer 30

Stem cells: Type A dense Mitotically active: Type A pale Final mitotic division: Type B pale