B2.3 Cell specialisation Flashcards
What are the stages of human development in order?
Gametes, zygote, embryo, fetus, infant, adult
Cell differentiation
Some of the genes in the cell are switched off or switched on during different stages of cell divisions according to their destined role.
Cell signalling
The process of information being transferred from the surface to the nucleus of a cell. It controls gene expression and therefore differentiation.
Morphogens
Signal molecules that control cell differentiation.
Different concentrations (gradients) of signalling molecules cause…
Different genes being expressed in different parts of the embryo and .˙. different parts of the embryo developing different features.
Stem cells
Cells that are able to continually divide and differentiate into any type of cell. They are not specialised cells.
Where can stem cells be found?
In the meristematic tissue of root and stem tips.
Stem cell niches
The areas within tissues such as bone marrow, skin, muscle and liver that house stem cells.
What do daughter cells of stem cells become?
Either:
1. More stem cells (.˙. self renewing the population
2. Differentiate to a different cell type (can no longer differentiate)
Totipotent
Only exist in early stages of embryo development. They can: continually divide, produce any tissue in the organism, form a complete organism.
Pluripotent
Come from totipotent cells and only exist in the early embryonic stage. Mature into almost all of the different cell types in an organism. Cannot produce a complete organism
Multipotent
Only form a limited number of cell types. Make up bone marrow tissue produces different types of blood cells. Occur later in embryo development and remain for the organisms life.
Unipotent
Only forms a single cell type, such as sperm in mammals. Form late in the embryonic stage and exist in the functioning organism.
Where are striated muscle fibres found?
skeletal muscle
what do the striations (bands) across striated muscle fibres allow?
muscle contraction
What is the advantage of cells being small and having a large surface area
They can use diffusion as an effective method to transport material (such as gases and water) into the cell
As cells get larger their surface area:volume ratio gets…
Smaller, causing diffusion into and out of cells to become inefficent
What are three things larger cells need?
- Some means of support
- Enough DNA to support the protein needs of the cell
- An efficient transport system
Why have many organisms become multicellular?
To overcome the restrictions of small cell sizes
What happens when cells get larger?
Their surface area:volume ratio decreases. The rate of diffusion stays the same, causing the extent to be less.
What are the 5 adaptations larger cells may have to overcome the problems of their size?
- Changes in cell shape
2.Cellular projections into and out of cells - Being located close to nutrients
- Methods of transporting waste
- The position of cells with respect to each other
What is the name of the shape of a red blood cell, and what is its advantage?
Biconcave disc shape, this allows them to be flexible and fit through the small capillaries
What are four adaptations of the cells that line the proximal convoluted tubule of the kidney?
- Closely stacked and cube shaped (space efficient)
- Microvilli (inc surface area, and .˙. absorption)
- Large numbers of mitochondria
- Channels at the base of cells to allow effective transport
Type 1 pneumocytes (alveoli)
- extremely thin (short diffusion distance .˙. more efficient, max rate)
- cover 95% of alveolar surface
- allow gas exchange between alveoli and capillaries
Type 2 pneumocytes (alveoli)
-5% of cells on alveolar surface
- produce pulmonary sulfactant (keeps alveoli from sticking together and collapsing)
Adaptations of type 2 pneumocytes (alveoli)
- cube shaped
- large area of cytoplasm (contains many organelles to produce the surfactant incl secretory vesicles)
- microvilli towards alveolar air space to inc surface area and surfactant secretion
- able to transform into type 1 pneumocytes if needed
How are cardiac muscle fibres connected?
Through specialised branched connections called intercalated discs (allows contractions to spread more quickly across the chambers of the heart)
How many nuclei do striated muscle fibres have?
multiple
How many nuclei do cardiac muscles have?
one
What is a feature of striated muscle cells membrane?
Nerve impulses can travel through it
What are the four adaptations of sperm?
- Haploid Nucleus (containing 23 instead of 46 chromosomes)
- Acrosome (containing enzymes to aid entry into egg through zona pellucida)
- Many mitochondria (aid movement)
- Flagellum (movement)
What are the 6 adaptations of eggs?
- Haploid Nucleus
- Fin stage of meiosis after fertilization
- Zona pellucida
- Vesicles/cortical granules
- cytoplasm rich in nutrients
- Follicle cells to nourish and protect egg
What do the haploid nuclei of both the sperm and egg form when fused?
A diploid zygote
Zona pellucida
A jelly like layer that hardens after a sperm has entered it to prevent polyspermy (more than one sperm fertilizing the egg)
Cortical granules (egg)
Release digestive enzymes into zona pellucida to prevent polyspermy
