Unit 7 Lesson 7: How Cells Are Used in the Body

Question 1

every cell in the human body is replaced every

Answer 1

seven years

Question 2

mitosis

Answer 2

a type of cell division in which a parent cell copies itself, resulting in two identical daughter cells. Mitosis is the form of cell division used in all cell growth except sexual reproduction.

Question 3

What does the parent cell do to divide

Answer 3

To divide, the parent cell first copies all the genetic information in its chromosomes.

Question 4

To divide, the parent cell first copies all the genetic information in its chromosomes. What are the copies called

Answer 4

Those copies are called sister chromatids.

Question 5

How do 2 sister chromatids form

Answer 5

The sister chromatids are then pulled apart and transported to different ends of the cell. The cell divides at its center, forming two daughter cells, each with a single set of chromosomes.

Question 6

prolilferation –

Answer 6

the increase in number of cells by replication

Question 7

Proliferation, in the cell cycle, simply means

Answer 7

growth

Question 8

During proliferation an organism’s cells

Answer 8

multiply over and over, giving that organism added mass and causing it to grow bigger.

Question 9

Growing organisms do not only add identical cells to become larger but also

Answer 9

specialize functions of cells to perform specific tasks.

Question 10

Multicellular organisms are made of many different kinds of tissue. To make all those tissues, an organism’s cells must also undergo

Answer 10

Differentiation

Question 11

differentiation

Answer 11

an increase in the specialization of a cell; Differentiation is the process by which less specialized cells become more specialized to fulfill specific functions.

Question 12

The chromosomes of every cell holds all its

Answer 12

genetic information.

Question 13

The chromosomes of every cell holds all its genetic information. That information is coded into the cell’s

Answer 13

deoxyribonucleic acid, or DNA.

Question 14

The DNA is made of t

Answer 14

two strands of nucleotides twined in a double helix.

Question 15

Nucleotides

Answer 15

. Nucleotides are a special type of molecule made of a ribose or deoxyribose sugar linked with a phosphate atom.

Question 16

DNA strands are like a cellular recipe book; elaborate

Answer 16

DNA strands are like a cellular recipe book in that they contain instructions for everything the organism needs to grow and develop. Each job a cell might do is coded onto part of its DNA strand.

Question 17

gene expression

Answer 17

the process in which instructions in DNA are used to produce a protein or other functional product

Question 18

Gene expression is the process by which a cell

Answer 18

reads a specific section of DNA’s nucleotides and becomes differentiated.

Question 19

What happens during gene expression

Answer 19

In gene expression, the cell creates a copy of some portion of a DNA strand’s nucleotides. The copy is made of ribonucleic acid (RNA). This copy will be read by the cell’s ribosomes which will then form the proteins it needs to carry out the specific function called for by that DNA segment.

Question 20

Not every cell can differentiate. Those that can are called

Answer 20

stem cells

Question 21

What are stem cells

Answer 21

Stem cells are unspecialized cells capable of unlimited proliferation (bounded only by their life span).

Question 22

What kind of cell can give rise to more specialized cells through gene expression

Answer 22

Stem cells can also give rise to more specialized cells through gene expression.

Question 23

How do stem cells produce different proteins which allow the cells to specialize.

Answer 23

By turning on or off the parts of the DNA script that are read, stem cells produce different proteins which allow the cells to specialize.

Question 24

What can affect a cell’s specialization

Answer 24

Scientists believe that environmental influence, nearby cells, and chemical signs can affect the cell’s specialization, known as the cell fate.

Question 25

cell fate

Answer 25

the outcome of the specialization of a cell based on environmental factors, chemical signs, and nearby cells

Question 26

Depending on its what, each stem cell differentiates into different cell types.

Answer 26

Depending on its cell fate, each stem cell differentiates into different cell types.

Question 27

Depending on its cell fate, each stem cell differentiates into different cell types.In humans, those include

Answer 27

In humans, those include bone cells, blood cells, epithelial cells (which line your skin, blood vessels, and organs), fat cells, muscle cells, nerve cells, immune cells, and skin cells. Each of those cell types has a specific function. These differentiated cells form the bones, blood, and other tissues of the growing organism.

Question 28

Cell differentiation and mitosis are used for more than growth. Elaborate

Answer 28

Cell differentiation and mitosis are used for more than growth. When an organism is injured or damaged, mitosis repairs it by replacing the damaged cells.

Question 29

What are platelets

Answer 29

Platelets, a kind of blood cell, respond to a signal from a damaged blood vessel.

Question 30

What do Platelets do when there a wound

Answer 30

They rush to the wound site to form a blood clot, which stops the bleeding.

Question 31

What do platelets do when they reach the wound

Answer 31

While they are there, the activated platelets continue to send out their distress signals, telling proliferating stem cells that more blood cells are needed.

Question 32

What do the blood cells do macrophages and neutrophils when they get to the wound

Answer 32

The other blood cells, macrophages and neutrophils, send out similar signals, stimulating more development.

Question 33

What is the role of basal cells and fibroblasts in the wound

Answer 33

The basal cells and fibroblasts that work to repair the skin and damaged blood vessels do the same. These newly specialized cells work together, filling in the wound and replacing damaged tissue until the organism is repaired.

Question 34

Do all cells have the same life spans

Answer 34

All cells have their own life spans. Some cells become senescent faster than others, but no cell lives forever.

Question 35

senescent

Answer 35

process in which cells exit the cell cycle and no longer divide but still carry out their function

Question 36

What are the properties of a senescent cell

Answer 36

A senescent cell is one that can no longer divide.

Question 37

What are cells like in complex organisms

Answer 37

In complex organisms, cells are constantly growing senescent and dying.

Question 38

life span of skin cells

Answer 38

Skin cells, for instance, live for 2–3 weeks.

Question 39

life span of colon cells

Answer 39

Colon cells last only four days.

Question 40

life span of bone cells

Answer 40

Some bone cells can live for up to 50 years.

Question 41

Some cells are not typically replaced by mitosis. Elaborate on heart cells

Answer 41

Heart cells never replicate inside an organism. They live as long as the organism.

Question 42

Some cells are not typically replaced by mitosis. Elaborate on brain tissue

Answer 42

In humans, brain tissue only replicates under very specific circumstances.

Question 43

Some cells are not typically replaced by mitosis. Elaborate on somes cells in the liver and pancreas

Answer 43

Some cells in the liver and pancreas can be replaced, while others do not replicate.

Question 44

The number of times a cell can divide before it is no longer able to propagate is called its

Answer 44

Hayflick limit

Question 45

Hayflick limit

Answer 45

concept that describes the number of times a normal human cell will divide before becoming senescent

Question 46

In 1959, a scientist named Leonard Hayflick cultured different kinds of cells in his laboratory. What did he observe

Answer 46

. He observed that human cells do not divide infinitely but instead die after 40–50 cell divisions. He was able to link this death to a cell’s telomeres.

Question 47

What are Telomeres

Answer 47

Telomeres are proteins found on the ends of a cell’s chromosomes. They are, essentially, junk information because they are not read as a part of the cell’s DNA. Instead, they act as protection for the rest of the chromosome, keeping its nucleotides from a gradual loss of information.

Question 48

What did Hayflick notice when a cell divides

Answer 48

Hayflick noticed that when a cell divides, it does not replicate itself entirely. Instead, for each cell division, the end of the telomere is snipped off, leaving it shorter. When a telomere becomes too short, the cell can no longer divide.

Question 49

When iw telomerase most active

Answer 49

Telomerase is most active during early development.

Question 50

When does telomerase production slow down

Answer 50

Its production begins to slow down during adolescence, and by late adulthood, it ceases.

Question 51

What happens when telomerase productiton stops

Answer 51

. When telomerase production stops, cells eventually cease to replicate, become senescent, and die.

Question 52

Hayflick discovered that cells go through three phases during their lifetimes. What’s the first phase

Answer 52

. In the first phase, when telomeres are at their longest, mitosis is rapid and healthy.

Question 53

Hayflick discovered that cells go through three phases during their lifetimes. What’s the second phase

Answer 53

In the second, as the telomeres shorten, cell replication slows down.

Question 54

Hayflick discovered that cells go through three phases during their lifetimes. What’s the third phase

Answer 54

The third phase is senescence. A cell which is senescent remains alive and functioning for a while, but eventually it dies. Cells can also die due to injury or poor health of the body.

Question 55

When most cells die, they are replaced by new cells. What does cell death indicate

Answer 55

Cell death acts as an internal signal to the stem cells to propagate and differentiate into the needed cell type. This replacement happens constantly throughout an organism’s body.

Question 56

But what about the cells that are never replaced?

Answer 56

Medical technologies using stem cells have successfully grown heart and brain tissue in the lab, but they are never replaced by mitosis within the organism.

Question 57

So, is your entire body replaced every seven years?

Answer 57

? No. Most of its cells may be, but some cells live much longer than seven years, and some are never replaced. You never get to become an entirely new person. The old story is interesting, but it is not true.

Question 58

If bone cells can live for up to 40 years, under what circumstances might your body make more of them before that amount of time?

Answer 58

Stem cells can diversify into bone cells to help an organism grow. Bone cells can also be replaced before their natural cell death if they become damaged. When you break a bone, the damaged cells are replaced as soon as the body can make them.

Question 59

Recent research into premature aging in mice has found that when telomerase from an outside source is added to a stem cell, telomere length can be reset, stopping the cell’s aging process. By adding telomerase from an outside source, there is a risk of uncontrollable replication. Leonard Hayflick opposes telomerase therapies. Consider what you have learned about proliferation and aging. What might cause a scientist to argue against the use of this kind of antiaging therapy?

Answer 59

By inducing a cell to replicate past its Hayflick limit, scientists could be said, essentially, to be creating the conditions for cancer. Since infinite replication opens up infinite possibility for harmful mutation, allowing a cell to continue replicating past the Hayflick limit virtually guarantees more instances of tumors and malignant overgrowth.

Question 60

Can cells differentiate without propagating? Explain why or why not.

Answer 60

No. In the cell cycle, differentiation happens after cells replicate. If a cell is fully grown, it no longer differentiates although it may still propagate.

Question 61

doctors treat snakebites with a serum called

Answer 61

antivenin

Question 62

How is antivenin made

Answer 62

To make antivenin, a captive snake is “milked” for its venom which is then used to synthesize antibodies that help a bite victim’s body fight the poison.

Question 63

Drawbacks of antivenin

Answer 63

Milking venomous snakes is dangerous and difficult. Each species of snake produces a different kind of venom, so a dose of antivenin only works for one specific kind of snake. Thus, the amount of venom available has always been small. With enough antivenin available, dying of a snakebite could be eliminated.

Question 64

Scientists have now invented a way to manufacture antivenin without milking snakes at all. Elborate on pluripotent cells

Answer 64

Pluripotent stem cells have been induced to differentiate into organ-specific cell types eventually developing simplified organs called organoids. After induced growth begins, organoids self-replicate and self-organize, growing into cultures that replicate the function of tiny livers, brains, or hearts without further input from the lab. Organoids simulate the organ’s function they replicate. For instance, gastrointestinal organoids can mimic digestion. Organoids can also be grown to mimic abnormalities. They have been used to study cancers.

Question 65

The journal Cell reports that researchers have now successfully grown snake gland organoids. Elbarote

Answer 65

The scientists take a small amount of coral snake tissue and nurture it in a dish . The snake stem cells grow into organoids that are, in this case, just one millimeter wide. The snake organoids produce the same toxins as the parent snake’s venom. Each tiny organoid can create a lot of venom, opening up the possibility that the world’s antivenin supply could, for the first time in history, meet the needs of all snakebite victims.

Question 66

The venom organoids being grown now come from coral snakes, but venomous snakes make different kinds of poisons. Why does culturing coral snake venom help in treating other kinds of snakebites?

Answer 66

Mitosis is a process that happens in all complex organisms. By culturing venom glands from coral snake stem cells, scientists have proven that venom glands can be grown, through mitosis and differentiation, for any kind of snake.