Lecture 26: Eukaryotic Cell Growth And Death

Question 1

Cells- all have same genome yet differ from each other

Answer 1

Individual cells differ in structure and function by using only some of their genes in a process called cellular differentiation

Question 2

What is the function of cell division?

Answer 2

• is the basis of reproduction
• enables growth to adult size
• replaces worn out or damaged cells

Question 3

Stem cells- divide and self renew

Answer 3

Stem cells have two characteristic not found in more differentiated cells.
Stem cells are able to divide indefinitely and they self-renew
Stem cells give rise to a wide range of mature cell types

Question 4

Cellular differentiation

Answer 4

Cells progressively divide through a series of steps from stem cell to stages of intermediate cell types until the final functional cell type is produced
The final cell types are ‘terminally differentiated’ and do not divide further

Question 5

The cell cycle

Answer 5

The cell cycle is an ordered set of events in life of a call and is divided into periods called mitosis and interphase. Most of cells life is spent at interphase.
3 stages of interphase:
1. G1 (Gap 1): cell grows in size and increases it supply if protein and number of organelles.
2. S phase: DNA is replicated (synthesised) ready for cell division, two copies if each chromosome are made in prep for cell division.
3. G2 (Gap 2): cell grows in size; a time of metabolic activity of the cell
Cell division at mitosis:
Cells divide at mitosis to produce 2 daughter cells. The daughter cells must contain exactly the same genetic information as the parent cells.
Cell cycle control points:
Cell cycle checkpoints are regulatory pathways that control the order and timing of cell cycle transitions eg G1 to S. They ensure that critical events such as DNA replication and chromosome segregation are completed correctly before letting the cell progress further.

Question 6

What are the features of growth of a normal eukaryotic cell?

Answer 6

1. Exhibit mortality: a cell cannot divide indefinitely. Cells reach senescence after 20-60 generations, after which division ceases
2. Density dependant inhibition: growth is inhibited by high cell density or crowding
3. Anchorage dependant: most eukaryotic cells need a surface to grow upon.

Question 7

Cell death

Answer 7

Cells may die in either of two distinct processes: apoptosis (programmed cell death) or necrosis (unexpected cell death)
1. Apoptosis:
-apoptosis removes unwanted cells in a controlled way
A) during apoptosis the genome if the cell is broken down
B) the cellular contents are fragmented into smaller pieces
C) the debris is consumed by nearby phagocytic cells that clean up the cell fragments
D) during apoptosis, cellular contents are not releases and inflammation does not occur

2. Necrosis
   - physical or chemical insults can lead to the lethal disruption of cell structure and activit
   - as necrotic cells begin to die they swell- eventually holds appear in the plasma membrane and intracellular Martians spill out into surrounding environment and inflammation may occur

Question 8

Cancer

Also what are the features of growth for cancer cells

Answer 8

Cancer is cells growing out of control
-cancer is a disease of the cell cycle. Cancerous cells do not have a properly functioning cell cycle control system, they divide excessively and invade other body tissue

Features if growth for cancer cells:

1. Immortal-can divide indefinitely if enough nutrients (never reach senescence)
2. Not inhibited- by high cell density or crowding
3. Anchorage independant- ie dint need a surface to grow on