B2.3 Cell Specialisation Flashcards
Which of the following are roles of stem cells in living organisms?
I. Growth of new organs
II. Replacement of damaged cells
III. Production of cells which could differentiate
IV. Produce new stem cells by mitosis
- All of the above
- I, II, and III only
- II and IV only
- II, III, and IV only
1
Which of the following correctly describe the differentiated cells in an individual plant such as the golden barrel cactusbarrel (Echinocactus grusonii) show in image B2.3.1?
- There are different organelles in different differentiated cells.
- There are different genes in each type of differentiated cells.
- The differentiated cells have identical genes in every cell type.
- The differentiated cells produce the same proteins in every cell type
3
What are essential properties of stem cells?
1. They are specialised and can divide by meiosis
2. They are specialised and can divide by mitosis
3. They can divide by mitosis and differentiate.
4. They can divide by meiosis and differentiate.
3
What is the cause of stem cells differentiated along different pathways to produce a variety of differentiated cells?
1. The genome of the cells is different
2. The differentiated cells produce the same proteins
3. Gene expression varies between different kinds of differentiated cells
4. Gene expression varies within identical cell types.
3
Use Graph in image B2.3.2 to estaimte the volume of a liver cell.
2000 vol/μm^3
Image B2.3.3 shows some cardiac muscle tissue
Cardiac muscle cells (image) have a mean length of 100 μm and an estimated volume of 8000 μm^3.
Explain why cell length and volume ratios are not constant for all cell types
Cell shape is not constant.
Cell shape is related to function.
Some cells have a structure that increases surface area.
For example, Ovum is more spherical and so has the smallest volume (for its mass) compared to other shapes. Cardiac muscle cells are long and branching tubes.
Suggest one reason why a human ovum has specialised to have a large volume.
Nutrient storage.
Sufficient nutrients for early growth after fertilisation/before embedding in uterine wall.
Sufficient organelles for growth/in early embryo mitosis occurs without growth.
Estimate the mean lengh of a cell with a volume of 1000 μm^3 using the trend line on graph in image B2.3.1
18μm
The horizontal error bars in B2.3.2 represent standard deviation. Suggest what the standard deviation signifies.
The variation /standard deviation is the length of the cell type.
The measurement error in measurements.
Simplified models are commonly used to investigate scientific phenomena. Outline the limitations in the use of a sphere to model surface area to volume ratio in cells.
Allows a (general) calculation of surface area to volume.
Cell shape is complex/exact calculations are difficult/cells of the same type vary in size and shape.
Cells are not spherical.
Cells have adapted shapes for example to increase surface area.
Using examples from human tissues, distinguish between pluripotent, totipotent, and multipotent stem cells.
Totipotent stem cells can differentiate and produce all cell types in an organism including all types of placental tissue. Example - (apical) meristem, zygote/early embryonic stem cells/blastula.
Pluripotent cells can produce all cell types except some embryonic tissues/(foetal) placental tissue.
Example - later embryonic tissue/morula cells/induced stem cells.
Multipotent cells can give rise to limited number of specilalised cell types.
Example - stem cell niches/example such as bone marrow/skin stem cells.
Explain the role of stem cells in a multicellular organism.
Stem cells retain the ability to divide.
Stem cells divide by mitosis
The cells produced by stem cells can differentiate
Division of stem cells produces new tissues
It can replace tissues or damaged cells.
Division of stem cells is important for growth.
A cell can be modeled on a sphere. Increasing cell size decreases the surface area to volume ratio for a sphere in the following manner (figures to 1 decimal place):
(Table in image B2.3.4)
a. Explain why a large surface area to volume ratio can increase cell efficiency.
b. Describe, using two specific examples, how cell adaptation can increase the surface area to volume ratio in a specialised cell.
a. Materials/metabolites are exchanged across the (cell) surface.
As the surface area to volume ratio decreases exchange (of materials become less efficient (or converse)
A large surface area allows fo efficient exchange/converse.
A large volume requires a greater amount of metabolites/relatively lower surface area to exchange them.
b. Microvilli
Thin/flat (rather than spherical) shape
Invagination (max 2 marks)
Examples - renal tubule cells, intestinal mucosa/lining, capillary wall, palisade cells, root hair cells or other relevant example
Many tissues found in plants are compound tissues, such as phloem tissue shown in B2.3.5. Phloem tissue transports organic nutrients from their site of production (often the leaf) to sites of storage or metabolism (often flowers or roots).
Compound tissues consist of several different cell types, simple tissues of only one cell type.
Outline why many tissues in multicellular organisms have more than one cell type in the tissue
Each cell type has a specific function.
Different types of cell are needed for the function of a tissue/ one cell type (generally) has 1 function.
Tissues may have several functions so need more than one cell type. (The idea that more than one cell type is needed for different tissue functions must be clear)
Credit for an example e.g. rods and cones of the retina/neurones and glial cells in the CNS.
