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Define what a stem cell is.
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Define what a stem cell is.
A stem cell is a cell that can divide (by mitosis) an unlimited number of times and has the potential to remain a stem cell or to develop into a specialised cell.
What are the properties of stem cells?
Stem cells have the capacity to divide endlessly and differentiate along different pathways.
What is cell differentiation?
Cell differentiation is the development of unspecialised cells (following fertilisation) into specialised cells.
What is the importance of the stem cell niche?
The stem cell niche can maintain cells or promote their proliferation and differentiation.
Give two examples of the location of stem cell niches in adult humans.
Two examples of the location of stem cell niches in adult humans are bone marrow and hair follicles.
What is meant by totipotency in stem cells?
Totipotent stem cells are stem cells that can differentiate into any cell type found in an embryo and can become cells that make the placenta.
What are pluripotent stem cells?
Pluripotent stem cells are embryonic stem cells that can differentiate into any cell type found in an embryo but are not able to differentiate into the cells of the placenta.
True or False?
Multipotent stem cells are adult stem cells that can differentiate into any cell type.
False.
Multipotent stem cells are adult stem cells that can differentiate into closely related cell types, for example, stem cells in bone marrow.
What type of stem cells are those found in cells in early-stage animal embryos?
Cells in early-stage animal embryos are totipotent.
How can a surface area to volume relationship be modelled? (NOS)
Surface area to volume relationship can be modelled using cubes of different side lengths.
Compare cell surface area with cell volume in relation to the exchange of materials.
The exchange of materials across a cell surface depends on its surface area whereas the need for exchange depends on cell volume.
As cells in size their surface area to volume ratio (SA:V) .
As cells increase in size their surface area to volume ratio (SA:V) decreases.
How is the size of male gametes (sperm cells) adapted to their function?
Male gametes are long and narrow to allow for streamlined movement/swimming toward the egg.
How is the size of red blood cells adapted to carry out their function?
Red blood cells are small to allow movement through narrow capillaries.
How is the size of muscle cells adapted for their function?
Muscle cells are larger than normal cells, and their longer length and diameter are designed to exert force during muscle contraction.
True or False?
Maximising the surface area to volume ratio is crucial for cells that require the movement of substances across the membrane.
True.
Maximising the surface area to volume ratio is crucial for cells that require movement of substances across the membrane.
Name two examples of cells that must have a large surface area to volume ratio.
Two examples of cells with large surface area to volume ratio are:
Red blood cells/erythrocytes
Proximal convoluted tubules
These are the examples given in the specification, however there are other correct example such as root hair cells and epithelial cells that line the small intestine.
Define the term biconcave.
Biconcave means having a shape that is concave on both sides, like a red blood cell.
Name two adaptations of a proximal convoluted tubule cell that increase the surface area to volume ratio of the cell.
Two adaptations of a proximal convoluted tubule cell are:
Microvilli
Invaginations
What is the definition of microvilli?
Microvilli are small hair-like projections found on the apical membrane of proximal convoluted tubule cells in the kidney, as well as other types of cell.
True or False?
The alveolar epithelium is only one cell thick, which provides a short diffusion distance.
True.
The alveolar epithelium is only one cell thick, which provides a short diffusion distance.
What is the main function of type I pneumocytes?
The main function of type I pneumocytes is to maximise the rate of gas exchange by providing a short diffusion distance.
Define the term "pulmonary surfactant".
Pulmonary surfactant is a solution produced by type II pneumocytes that contains hydrophobic tails and hydrophilic heads, forming a monolayer that reduces surface tension in the alveoli.
What is the role of pulmonary surfactant in the alveoli?
Pulmonary surfactant helps maintain the shape of the alveoli and prevents them from sticking together, as well as aiding gas exchange.
What are the properties of cardiac muscle?
Cardiac muscle is myogenic, can contract continuously without fatigue, and has specialised branched connections (intercalated discs) to allow rapid contraction across the heart.
What is the purpose of the transverse system tubules (T-tubules) in skeletal muscle fibres?
The T-tubules run close to the sarcoplasmic reticulum and allow signals to be conveyed to all parts of the muscle fibre at once.
What is the significance of the haploid nucleus in sperm cells?
The haploid nucleus in sperm cells can fuse with the haploid nucleus of an ovum to form a diploid zygote.
What is the role of the acrosome in sperm cells?
The acrosome in sperm cells contains digestive enzymes that help the sperm penetrate the zona pellucida of the ovum.
What is the purpose of the zona pellucida surrounding the ovum?
The zona pellucida can harden after fertilisation to prevent polyspermy (penetration by more than one sperm).
What is the function of the cortical granules in the ovum?
The cortical granules in the ovum contain digestive enzymes that are released into the zona pellucida to prevent polyspermy.