B2.3 Cell Compartmentalisation Test Revision Flashcards
Explain the importance of the surface area to volume ratio as a factor limiting cell size. [7]
As size increases both surface area and volume increase, but volume increases
more / ratio of surface area to volume decreases as size of cell increases;
b. Rate of metabolism is a function of its mass to volume ratio;
c. Surface area limits / affects the rate at which substances can enter (or leave) the
cell;
d. Volume determines the rate at which material is produced / used;
e. Oxygen / nutrients / substances will take too long to diffuse into / out of the centre
of the cell if it is too big;
f. Excretory products would take too long to be eliminated;
g. Heat will take too long to be eliminated;
h. Example of cell adaptation to increase the ratio of surface area: volume e.g. root
hair cell / microvilli of intestinal epithelium;
Explain why female gametes are larger than male gametes? [3m]
The larger body of the egg allows it to store nutrients for the early development of the fertilized eggs, whereas the tiny body of the sperm only needs a head and a flagellum- the head stores the nucleus with genetic material and the flagella helps propulsion to swim to reach the egg for successfull fertilisation.
Explain why there is a range of cell sizes in humans. 4m
Each differentiated cell is specialised for a specific purpose, and its size is aiding part of that purpose. For instance, red blood cells are smaller than white blood cells because they need to be small enough to fit through narrow lumen of capillaries. Also, by being smaller, they have a larger surface area to volume ratio to allow for greater oxygen uptake and faster diffusion of oxygen in and out of the cell. However, white blood cells are larger than red blood cells because they need to large enough to engulf foreign pathogens such as bacteria and viruses or to produce antibodies that bind to the and kill them.
Explain why striated muscle fires are multinucleated? 2m
Striated muscle fibres are multinucleated cells that attachj to muscle to allow for movement. Instead of being made from any individual cells, muscles fibres are extended cellular structures which allow them to coordinate contraction and have a significant effect on muscle force generation.
Explain the effect of morphogens in cell specialisation. 3m
Morphogens are molecules which chemically transmit which genes to express. Occuring in the early-stages of embryo development, morphogenes are involved in gene expression. Morphogens are extracellular and occur on a gradient of concentrations. It is the gradient of concentrations which drives the process of differentiation of unspecialised stem cells into different cell types. Where there is a high concentration of morphogens, these cells will change differently to cells where there is a lower concentration of morphogens. Thus the inhibition or expression of a gene is a result of differing morphogen expressions. These morphogens also determine the next series of cascades/signals. Responses to these signals determines the direction and extent of cell growth and development, ultimately forming the tissues and organs of the body.
Distinguish between totipotent, pluripotent, multipotent and unipotent cells.
Totipotent cells have the ability to form an entirely new organism and are the least differentiated. Together with the pluripotent cells, they form embryonic stem cells. Totipotent cells can also form placental cells and are found in the first cells following fertilisation.
List the differences between embryonic and adult stem cells
While embryonic stem cells can give rise to all types of cells of an adult organism through continual cell division. Adult stem cells are undifferentiated cells capable of cell division but only give rise to a limited range of cells within a tissue. For instance, blood stem cells can only give rise to red,white blood cells and platelets only.
The emryonic stem cells also make up the bulk of the embryo as it begins development. However, adult stem cells, occuring within most organs and for the purpose of replacing damaged or dead cells, found on bone marrow, brain or liver.
Define the term stem cell niche
A stem cell niche is a specific microenvironment in the body that either maintains the stem cells or promotes their proliferation and differentiation.
Explain the function of stem cell niches
A stem cell niche is a specific microenvironment in the body that either maintains the stem cells or promotes their proliferation and differentiation. In hair follicles, the stem cell niches are located between the opening of the sebaceous gland and attachment site of hair erector muscle. They are known as bulge hair follicle stem cells. In the bone marrow, the bone marrow within the skeleton is the site of blood cell formation. In human adults, oseteoblasts and haemtopoietic stem cells are closely conneted in bone marrow. Haematopoietic cells produce red blood cells, white lood cells and platelets. Cells that give rise to mature skeletal cells are critical in teh regulation of HSCs.
Define the term totipotent
They can become any type of body cell. They can form more totipotent stem cells. They can form cells that make up the placenta
How do cell sizes correspond to function? (Female and male gamete, red and white blood cells, Neurons, striated muscle cells) 7m
What is determined a cell’s surface area?
The rate at which materials can enter and leave a cell depends on the surface area of the cell. Addotionally, the heat transfer between the cytoplasm and the environment is also determined by surface area.
Explain the effect of increasing cell size on the efficiency of diffusion in the removal of metabolic waste products from cell cytoplasm.
As cell size increases, efficiency of diffusion in removal of emtabolic waste products of cell cytoplasm decreases. Volume increases faster than surface area, so surface area to volume ratio falls. Hence with increasing cell size, less and less of the cytoplasm has access to the cell surface for exchange of gases, supply of nutrients and loss of metabolic waste products.
State the effect on the SA:Volume ratio as the cell increases in size
