Biology Chapter 4 - Stem Cells Flashcards

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Questions and Answers

What are differentiated cells?

Specialized cells that carry out specific functions.

How are stem cells different from differentiated cells?

Stem cells can become any other cell type, whereas differentiated cells do not become other cells.

In human development, what happens to the initial embryonic stem cells to make them become other kinds of cells?

They receive chemical signals that inactivate genes that cause the cell to differentiate.

What does the ectoderm become?

Skin and nervous system. Signup and view all the answers

What does the mesoderm become?

Blood vessels, bone, muscle. Signup and view all the answers

What does the endoderm become?

Digestive tract, respiratory system, glands like pancreas and liver. Signup and view all the answers

How many different cell types are there?

About 250. Signup and view all the answers

What are somatic stem cells?

Adult stem cells. Signup and view all the answers

What role do somatic stem cells play in adults?

Help repair the body and replace damaged cells. Signup and view all the answers

How are somatic stem cells different from embryonic stem cells?

Somatic stem cells can only become a few types of cells, whereas embryonic stem cells can become many types of differentiated cells. Signup and view all the answers

Where are somatic stem cells found in the body?

Surrounded by niche cells in the brain, blood, heart, teeth, liver. Signup and view all the answers

Is cell differentiation final and irreversible?

False (B) Signup and view all the answers

How is the DNA arrangement different in a stem cell compared to a differentiated cell?

DNA in stem cells is not tightly wrapped, while in differentiated cells it's tightly wrapped. Signup and view all the answers

How does DNA tightening affect gene expression?

DNA tightening inactivates or turns off genes. Signup and view all the answers

How many genes are needed to convert a somatic cell back to a stem cell?

As few as 4. Signup and view all the answers

What is an iPS cell?

Induced pluripotent stem cells; it is a cell that has been converted from a differentiated cell back to a stem cell. Signup and view all the answers

What do niche cells do for stem cells?

Protect and keep stem cells from differentiating. Signup and view all the answers

What activates the stem cell?

Chemicals from the environment called signals. Signup and view all the answers

What do these signal chemicals do to the DNA?

Activate or turn on genes that make different types of cells from stem cells. Signup and view all the answers

Match the following cell niches with the differentiated cells produced:

Blood = Red blood cells Bone = Bone cell/Osteoblasts Intestine = Intestinal absorptive cells Hair = Hair follicle cells Brain = Neurons, Glial Cells Signup and view all the answers

What is the function of red blood cells?

Carries oxygen throughout the body to all the cells. Signup and view all the answers

What is the function of bone cells?

Builds and repairs bones by excreting collagen. Signup and view all the answers

What is the function of intestinal absorptive cells?

Absorb nutrients from the intestine into the blood. Signup and view all the answers

What do hair follicle cells do?

Make hair fibers. Signup and view all the answers

What is the function of neurons?

Send signals. Signup and view all the answers

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Study Notes

Stem Cells Overview

Differentiated cells are specialized cells that perform specific functions.
Stem cells are unique in their ability to become any other cell type, while differentiated cells are limited to their specific roles.

Embryonic Development

Initial embryonic stem cells differentiate into various cell types through chemical signals that deactivate certain genes.
Three primary germ layers arise during development:
- Ectoderm: develops into skin and the nervous system.
- Mesoderm: forms blood vessels, bones, and muscles.
- Endoderm: becomes the digestive tract, respiratory system, and glands like the pancreas and liver.

Cell Types and Stem Cells

The human body contains approximately 250 different cell types.
Somatic stem cells, also known as adult stem cells, are responsible for repairing tissues and replacing damaged cells.
Somatic stem cells have limited differentiation potential compared to embryonic stem cells, which can develop into a wider variety of cell types.

Location and Differentiation

Somatic stem cells are found in niche environments throughout the body, including the brain, blood, heart, teeth, and liver.
Cell differentiation is not necessarily irreversible, allowing potential reversion to a previous state.

DNA Structure and Gene Expression

In stem cells, DNA is loosely arranged, enabling gene expression. In contrast, tightly wrapped DNA in differentiated cells restricts gene activation.
DNA tightening during differentiation may silence genes, preventing the cell from reverting to a stem state.

Induced Pluripotent Stem Cells

Induced Pluripotent Stem (iPS) cells are created by reprogramming differentiated cells back into a stem cell state using a minimum of four genes.

Role of Niche Cells

Niche cells provide protection and ensure that stem cells remain undifferentiated, regulating their development through environmental signals.

Functional Cell Niches

Blood niche: produces red blood cells, which carry oxygen using hemoglobin; no organelles are present.
Bone niche: generates osteoblasts, crucial for building and repairing bones; secretes collagen.
Intestinal niche: forms intestinal absorptive cells with microvilli that enhance nutrient absorption.
Hair niche: gives rise to hair follicle cells that synthesize strong hair fibers via keratin.
Brain niche: produces neurons (signal transmission) and glial cells (support neuron function), featuring long dendrites for communication.