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Question 1

contact inhibition

Answer 1

While the cell bodies of neighboring cells may cross each other, their nuclei never overlap. Once cell reaches confluence, contact inhibition signals cells to stop growing

Question 2

Confluence

Answer 2

the percentage of the culture dish surface covered by a layer of adherent cells, with 100% confluence meaning the dish is fully covered with no gaps between cells.

Question 3

Quiescence

Answer 3

Growth arrested cells

This is the case in mammals everywhere but the epithelial tissues of the intestines

Cells in vitro have undergone treatments and divide unlike their quiescent counterparts

Question 4

What is purposeful cell death for

Answer 4

• Provide space for cell growth
• No longer needed
• Infection

Question 5

Types of apoptosis

Answer 5

Extrinsic - mediated by death receptor

Intrinsic: stress signals cause

Question 6

Cell growth system controls

Answer 6

Positive factors: promote increasing cell mass/cell division, suppress cell death
Availability of nutrients, growth factors, mechanical tension through the cytoskeleton and surface adhesion

Negative factors: promote programmed cell death, suppress growth
Sensing presence of death signal, apoptosis-triggering stress

Question 7

G0 cell cycle

Answer 7

Proliferative cells go through the G₁, S, G₂, and M phases of the cell cycle

Quiescent cells exit G₁ and enter G₀:
G₀ can be reversible and the differentiated cells returned to the G₁ phase (e.g., hepatocytes), or irreversible for terminally differentiated cells (e.g., nerve cells)

Major professional secretory cells in the human body (hepatocytes, plasma and pancreatic cells) are at G₀ phase

Question 8

What regulates the cell cycle

Answer 8

The progression of the cell cycle is regulated by different cyclins, Cdks, and CDI inhibitors, each of which is dynamically expressed

Question 9

Pluripotent

Answer 9

Can make all types of specialized cells in the body
Embryonic stem cells are pluripotent

• Pluripotent stem cells can form all three germ layers including germ cells, but not the extraembryonic tissue as placenta and umbilical cord. Cells of the inner cell mass of the blastocyst are pluripotent. When these cells are brought into culture, they are called embryonic stem cells (ESCs).

Question 10

Totipotent

Answer 10

• Totipotent stem cells can form an entire organism. The fertilized oocyte and the cells after the first cleavage divisions are considered totipotent.

Question 11

Multipotent

Answer 11

Can make multiple types of specialized cells, but not all types Tissue stem cells are multipotent

Question 12

Oligopotent

Answer 12

• Oligopotent stem cells can differentiate into two or more lineages, for example, neural stem cells that can form a subset of neurons in the brain.

Question 13

Unipotent

Answer 13

Unipotent is the ability to form cells of a single lineage, for example, spermatogonia stem cells.

Question 14

Potency

Answer 14

Measure of how many types of specialized cell a can make

Question 15

Morula and blastula

Answer 15

• Early development starting from the fertilized egg (zygote)
• The zygote then forms the morula, a solid ball of cells which then forms a fluid-filled space termed the blastula, where the outer layer is composed of trophoblasts that will form the placenta and an inner cell mass that will form the embryo.

Question 16

Mesoderm

Answer 16

• The cells between the inner and outer cell layers are known as
  the mesoderm and will form most of the internal organs.
• At this stage, cells from one presumptive layer are not yet determined to be ectoderm, mesoderm, or endoderm as transplanting cells from one layer to another, the cells will adopt the phenotype of the layer to which they are transferred.

Question 17

Stem cell categories

Answer 17

• Stem cells can proliferate and differentiate to become cells with new phenotypes and functions.
• The field can be divided into adult, embryonic and induced stem cells

Question 18

What can happen when SC divide (2 options)

Answer 18

They self-renew or differentiate into specialized
cells

Question 19

Blood stem cells

Answer 19

Individual white blood cells live for 1-3 days, and all your red blood cells are replaced every 120 days by hematopoietic stem cells (HSCs) in the bone marrow.

Question 20

Do cardiomyocytes regen?

Answer 20

Yes but cardiomyocyte turnover is very slow, and a 50-year-old person has replaced only about half of his/her cardiomyocytes present after their first birthday.

Question 21

Central nervous system regeneration?

Answer 21

The central nervous system—brain and spinal cord—was thought not to regenerate but research over the last 15 years has shown the cells of these tissues may renew slowly.

Question 22

Skeleton regeneration rate and cells

Answer 22

Your whole skeleton is replaced every 6–8 years by the combined actions of the osteoclasts which remove and remodel the calcified bone matrix, and the osteoblasts which divide and then differentiate into new osteocytes and produce extracellular matrix which becomes cross-linked and calcified over time.

Question 23

induced PSCs

Answer 23

Adult somatic cells can be isolated and reprogrammed by transfection with a combination of immortalizing genes to produce the induced pluripotent stem cells (iPSCs)

Question 24

Self-renewal

Answer 24

Self-renewal refers to the ability of a stem cell to divide and make identical copies of itself to assure that the stem cell population is not depleted, and exists throughout development, and some may remain for the life of the organism.

Self-renewal in vivo requires a specialized location—the stem cell niche—where stem cells are maintained through the action of support cells nearby.

Question 25

Asymmetric division

Answer 25

• Self-renewal allows the proliferation of stem cells, or it can produce one daughter cell that is a stem cell and one daughter cell that then proceeds along a differentiation pathway.
• This asymmetric division may be caused by cell fate transcription factors accumulating unequally in one daughter cell or can be caused by signals outside the cell, such as another cell or a gradient of morphogens, or growth factors from the nearby tissue.

Question 26

Why self-renew and differentiate

Answer 26

1 stem cell
Self renewal - maintains the stem cell pool

4 specialized cells
Differentiation - replaces dead or damaged cells throughout your life

Question 27

TACs

Answer 27

most rapidly dividing cells are the transit-amplifying cells (TACs)

Question 28

Time differentiation SCs

Answer 28

20-30h

Question 29

How many SCs one cell make

Answer 29

A single cell dividing every 24 h can produce 1 million cells in 21 days and 1 billion (109) in 31 days.

Question 30

EpSC

Answer 30

epidermal stem cell

Question 31

cryopreservation

Answer 31

Freezing (here stem cells) to keep for later

With SCs we use dimethylsulfoxyde to prevent formation of ice crystals breaking the membrane

Question 32

Passaging

Answer 32

The cells in the culture vessel must be subcultured into two to four new culture vessels with fresh nutrient medium.
* This step is referred to as “passaging” the stem cells, and each passage usually represents three to four doublings of the stem cells.
* Stem cells are often cultured this way to keep them in log phase growth to produce millions of cells in a predictable time period.

Question 33

Cell division and cell human numbers

Answer 33

A single cell dividing every 24 h can produce 1 million cells in 21 days and 1 billion (109) in 31 days

30 cell division cycles represent 1,073,741,824 or ∼1 billion cells

There are approximately 37 trillion cells that make up the human body

Question 34

Stem cell differentiation and cause

Answer 34

• Differentiation is the process whereby stem cells become more specialized cell types and can perform new functions by expressing new genes, mRNA, and proteins.
• Differentiation involves the deactivation of some genes and the activation of a new set of genes.
• Differentiation can be caused by a change in basal nutrients, a change in the cell’s environment, a stimulation, or a lack of stimulation of a signaling molecule, a new cell-to-cell interaction, etc.

Question 35

Zygote

Answer 35

Definition: A fertilized egg formed when DNA from both parents’ genetic material combines. Marks the beginning of embryonic development.

Question 36

Blastomeres

Answer 36

Definition: Cells produced by the division of a zygote. Early embryonic cells during the initial stages of cell division.

Question 37

Morula

Answer 37

Definition: An early stage embryo consisting of 16 totipotent cells, forming a solid ball without an internal fluid compartment. Leads to the differentiation of outer cells into trophoblasts and inner cells into progenitors.

Question 38

Blastocyst

Answer 38

Definition: An advanced stage in embryonic development characterized by a fluid-filled internal cell mass. The outer cells (trophoblasts) contribute to forming the placenta, while the inner cells give rise to the embryo. It’s the stage used for embryonic stem cell collection and typically for implantation in IVF.

Question 39

Embryonic Stem Cells

Answer 39

Definition: Pluripotent cells derived from the inner cell mass of the blastocyst, capable of differentiating into any cell type, thus holding potential for regenerative medicine and research.

Question 40

Endoderm

Answer 40

Definition: One of the three primary germ layers in the embryo that forms the innermost layer. Gives rise to the digestive tract, liver, pancreas, and other internal organs.

Question 41

Ectoderm

Answer 41

Definition: The outermost germ layer of the embryo. It develops into the skin, brain, nervous system, and other external tissues.

Question 42

SC differentiation def and causes

Answer 42

Process whereby stem cells become more specialized cell types and can perform new functions by expressing new genes, mRNA, and proteins.
(deactivation of some genes and the activation of a new set of genes)

Can be caused by a change in:
- basal nutrients
- cell’s environment
- stimulation, or a lack of stimulation of a signaling molecule
- new cell-to-cell interaction

Question 43

Where are embryonic vs tissue stem cells found

Answer 43

embryonic in the early blastocyst, tissue in fetus, baby and adult

Question 44

Whats homeostasis in terms of stem cells

Answer 44

requires the loss of cells to be accurately balanced by cell replacement.

Question 45

Stem cell proliferation

Answer 45

Proliferation of stem cells allows the single cell zygote—the ultimate stem cell—to grow into an adult organism.
* During this time, tissues and organ systems develop and become fully functional.