Stem Cells Flashcards
What is a Stem Cell?
A cell which can divide (by mitosis) an unlimited number of times.
What does each new cell have the potential to do?
To remain a stem cell or to develop into a specialised ell by differentiation.
What is potency?
The ability of stem cells to differentiate into more specialised types.
What is Totipotency?
Totipotency stem cells can differentiate into any cell type found in an embryo as well as extra-embryonic cells.
What is Pluripotency?
Pluripotent stem cells are embryonic stem cells that can differentiate into any type of cell found in an embryo but not into extra-embryonic stem cells and are no longer pluripotent.
What is Multipotency?
Multipotent stem cells are adult stem cells that have lost some of the potency associated with embryonic stem cells and are not longer pluripotent.
What happens as tissue, organs and organ systems develop?
Cells become more and more specialised.
What happens, specifically to adult cells, when they have differentiated and specialised to fulfil particularly roles?
Most adult cells gradually lose the ability to divide until they are no long able to divide.
What remains to produce new cells? An for what processes?
Small number of stem cells (adult) remain to produce new cells or the essential process of growth, cell replacement and tissue repair.
How many times can adult stem cells divide and what types do they produce?
By Mitosis and unlimited number of times, only able to produce a limited number of times-Multipotent.
There is research into stem cell therapy. What is this?
The introduction of adult stem cells into damaged tissue to treat diseases and injuries.
Where are stem cells found?
-Bone Marrow
What type of cells is bone marrow?
Multipotent adult stem cells
What can these cells differentiate into?
Only erythrocytes (RBC), monocytes, neutrophils and lymphocytes
What are Erythrocytes?
Red Blood Cells
What is the main function of Erythrocytes?
Transport of oxygen around the body as well as the transport of carbon dioxide.
Why are new Erythrocytes constantly being formed from bone marrow stem cells?
As RBC lack a nucleus so cannot divide so new erythrocytes are made to maintain the RBC count
What is the first stage in Erythropoiesis?
The cell is Multipotent: It divides to form Proerythrocytes.
What is the second stage in Erythropoiesis?
Change have occurred and this cell can now only form and erythrocyte.
What is the third stage in Erythropoiesis?
Haemoglobin builds up in cytoplasm.
What is the fourth stage in Erythropoiesis?
Nucleus is ejected.
What is the fifth stage in Erythropoiesis?
Further changes form a mature erythrocyte.
What does this mature erythrocyte look like from above?
-No nucleus-room for haemoglobin.
-Cell is full of haemoglobin pigment which absorbs oxygen
What does this mature erythrocyte look like from the side?
Biconcave shape giving a greater surface area for oxygen absorption.
What happens during Erythropoiesis which allow it to function as an erythrocyte?
Changes occur that adapt the structure of the original stem cell.
What are some of these adaptations?
-Changing to biconcave shape
-Elastic Membrane-
-Ejection of nucleus and other organelles
-Building up of haemoglobin in cytoplasm.
What does the adaptation to the biconcave shape allow?
Large surface area allowing more oxygen to be absorbed through cell surface.
What does the adaptation an elastic membrane allow?
Change shape and get through narrow capillaries.
What does the adaptation of the ejection of the nucleus and other organelles allow?
-more room for haemoglobin
-increases oxygen capacity
What does the adaptation of the building up of haemoglobin in cytoplasm allow?
Haemoglobin binds with oxygen and only release when oxygen concentrations decrease to low.
How are neutrophils formed?
The same stem cells that form erythrocytes.
What are neutrophils?
A type of white blood cell.
What are the main changes as stem cells differentiate into neutrophils?
-Indentation form the nucleus, giving it a lobed structure.
-Granules accumulate; are lysomes that contain hydrolytic enzymes.
Neutrophils are WBC. What is the first step in the function they play?
Are the first WBC to arrive at the infection site or in the body.
Neutrophils are WBC. What is the second step in the function they play?
Exit the blood through tiny gaps in the capillary walls and collect around foreign bodies.
Neutrophils are WBC. What is the third step in the function they play?
Destroy foreign bodies by engulfing them by phagocytosis and digesting them using their hydrolytic enzymes.
What are some of the adaptation of neutrophils?
-Flexible shape and flexible nuclear membrane
-Contains many lysomes
What does a flexible shape and flexible nuclear membrane allow?
Neutrophils to fit between cell walls to form pseudopodia
What do many lysomes contain and therefore do?
Contain hydrolytic enzymes which destroy invading cells.
What form the transport system in plants?
-Xylem Vessels
-Phloem Sieve Tissues
Where are Xylem Vessels and Phloem Sieve Tissues found?
In plants roots and stems
Where are Xylem and Phloem formed?
From stem cells found in the tissue between them.
What is the tissues between them known as?
Cambium
What is Cambium?
A meristem
What is a meristem?
The term given to to any undifferentiated cell in a plant which has the ability to give rise to new cells.
Give an example of meristems.
Meristems located at tips of shoots and roots that provide new cells to these growing parts of the plant.
At the roots and shoots of plants, what do the stem cells at the inner edge of the cambium differentiate into?
Xylem cells
At the roots and shoots of plants, what do the stem cells at the outer edge of the cambium differentiate into?
Phloem cells.
What happens when they differentiate into xylem?
-lose cytoplasm
-deposit lignin in their cell walls
-lose their end cells walls
What happens when they differentiate into phloem?
-lose some cytoplasm and organelles
-develop sieve plates at the end of the cells
What is this cambium cell differentiation stimulated by? And how does it work?
By hormones- the balance of hormones determine if xylem or phloem.
What are the 4 sources of stem cells?
-Embryonic stem cells
-Umbilical chord
-Adult stem cells
-Induced pluripotent stem cells
Where are embryonic stem cells present?
In an early embryo formed when the zygote begins to divide
Where are umbilical chord stem cells present?
In umbilical chord blood
Where are adult stem cells found?
Developed tissues amongst the differentiated cells which act as a repair system.
Where are induced pluripotent stem cells developed?
In labs by reprogramming differentiated cells to switch on certain genes and become undifferentiated.
What are 4 uses of stem cells in research an medicine?
-Bone marrow transplant
-Drug research
-Developmental biology
-Repair of damaged tissues or replacement of lost tissues.
Explain the use of stem cells in a bone marrow transplant.
-Treat disease of the blood and immune system.
-Restore blood system after types of cancer
Explain the use of stem cells drug research.
If stem cells can develop types of human tissues, new drugs can be tested on that.
Explain the use of stem cells in developmental biology.
Can be used and enable a better understanding of how multicellular organisms develop, grow and mature.
Explain the use of stem cells in the repair of damaged tissues or replacement of lost tissues
-Treat mice with type 1 diabetes
-Bone marrow into liver cells to treat liver disease
-Into nerve tissue to treat Alzheimer’s
-Regenerative medicine
