Studied by 3 people
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Specialised cell examples (humans)
Muscles
Lungs
Eggs
Sperm
Specialised cell examples (plants)
Root cells
Stem cells
Versatile, unspecialised cells within an organism that can either specialise or remain stem cells to facilitate development of new cells
Stem cells plants example
Meristematic tissue - found in buds and stems, can differentiate into any type of tissue
Cell reproduction allows
Growth, replacement of dead/damaged cells
Zygote development + specialisation
The cells are initially unspecialised but differentiate quickly, which is a result of genes being expressed. Every cell contains all the genetic information needed to create the whole organism.
Cell signalling
Process of information being transferred from cell surface to nucleus. Signalling controls gene expression and thereby differentiation.
Morphogens
Signal molecules that control cell differentation - found in gradients in different regions of early embryos. The concentration of them dictates regional development within the embryo. The gradient of them results in different parts of the embryo developing different features.
Specialised cell reproduction
Some cells partially or entirely lose the abolity to reproduce when they become specialised (nerve and muscle cells) while others retain the ability, reproducing the same type of cells (skin and epithelial cells)
Stem cells self-renewal
The ability of stem cells to reproduce more stem cells and continue reproduction indefinitely
When do cells become differentiated?
When cell signalling ensures that specific genes are expressed in the cell
Stem cell niche examples humans
Hair follicles and bone marrow
What do stem cell niches have in common?
Signalling factors that bring about both self-renewal and differentiation
Totipotent cells
Only exist in very early embryonic stages. Capable of continuous division, can produce any tissue in the organism. Can form a complete organism
Pluripotent cells
Also only exist in early embryonic stages. Can mature into almost all cell types within an organism, but cannot form a complete organism.
Multipotent cells
Able to differentiate into several cell types, but only in closely related areas. I.e hair follicle cells, which are associated with oil glands, hair, skin and nail reproduction, etc.
Unipotent cells
Form in the late embryonic stage, only forms a single cell type (i.e sperm cells)
Are stem cells visibly distinguishable by their appearance?
No, only by their behaviour
How could stem cells help cure certain diseases/illnesses?
By replacing depleted differentiated cells lost to injury or disease (such as brain or muscle cells)
What determines cell size?
Cell function, cell division apparatus
Smallest human cell?
Sperm cell - all they do is carry genetic material to form a zygote
Largest human cell?
Nerve cell
Red blood cell adaptations
Concave shape - increases surface area
Contain haemoglobin which can bind with/release oxygen
No nucleus or mitochondria
Smaller, can travel through narrow capillaries
Why are white blood cells larger?
Neccesity for nucleus, granules, and organelles, as well as more enzymes which break down pathogens
Axons
Long fibres in nerve cells which carry impulses up and down the body pver long distances
Why are nerve cells so long?
To efficiently transmit impulses from the brain throughout the body
Functions of (dependent on) cell volume
Rate of heat and waste production
Rate of resource production
Function of (dependent on) surface area
Movement of materials in and out of cells
Why are cells so small?
Cells are limited by the size they can reach and still (efficiently) carry out functions of life. Therefore, larger organisms have more rather than larger cells.
