1.1 Introduction to Cells Flashcards
What is the magnification equation?
image size/real size
What are the three exceptions to the cell theory?
- Striated muscle - longer than most animal cells, in humans about 30mm. They have many, maybe several hundred nuclei.
- Aseptate hypha - In hypha normally the fungi structures are separated into sections by septa however in these there are no septa, so each structure is uninterrupted with many nuclei.
- Algae, can be giant ip to 100mm and only one cell, you would normally expect it to be more.
What are the functions of life?
M - metabolism R - reproduction S - sensitivity G - growth H - HOMEOSTATSIS E - excretion N - nutrition
What are cell limitations?
Surface area, reactants need to be absorbed and waste products excreted, this needs to happen over the surface area of the membrane. Also for heat loss.
Investigate functions of life in Paramecium and one named photosynthetic unicellular organism?
Paramecium -
M - Metabolic reactions take place in the cytoplasm
R - Nucleus reproduces asexually
S - Beating of the cilia moves the cell through the water in response to the environment
H - Contractile vacuole at each end of the cell fill up with water and then expel it.
G - It grows
E - Waste products diffuse through the membrane
N - Food vacuoles contain smaller organisms that the Paramecium has consumed.
CHLAMYDOMONAS
M - Metabolic reactions take place in the cytoplasm
R - Nucleus can reproduce sexually or asexually
S - Beating of two flagella moves it through the water, following a sensitive eyespot.
H - Contractile e vacuoles
G - Grows by photosynthesis
E - Cell wall freely permeable
N - Cell wall freely permeable
What are emergent properties?
Emergent properties arise from the interaction of the component parts of a complex structure. ‘The whole is greater than the sum of its parts’.
Cells in a multicellular organism differentiate, then they can carry out their role more efficiently than if they had many different roles. They can develop the ideal structure, with the enzymes needed to carry out all the chemical reactions associated with the function.
How do cells differentiate?
Each cell in our bodies, no matter of its job, have all the genes needed to specialise in every possible way. The development of a cell involves switching off all the genes that are not needed and then they are not expressed. Cell differentiation happens because a different sequence of genes is expressed in different cell types.
What are the cells called at the start of life?
A sperm fertilises an egg to form a zygote then it multiplies and forms an embryo.
What are stem cells?
These are extremely versatile cells that can differentiate along different pathways into any of the cell types found in that particular animal.
Why are stem cells useful?
- Because they can divide again and again to provide copious quantities of new cells. They are therefore useful for the growth of tissues or the replacement of cells that have been lost or damaged.
- They are not fully differentiated. They can differentiate in different ways, to produce different cell types.
We can use them to produce regenerated tissue, such as skin for people who have suffered burns. Or to heal diseases such as type 1 diabetes where a particular cell type has been lost or malfunctioning. Or perhaps to grow replacement organs.
To produce large amounts of meat for human consumption.
Where are stem cells in adults?
Bone marrow, skin and liver.
What is Stargardt’s disease?
Stargart’s macular dystrophy. It is a genetic disease that develops in most children between the ages of six and twelve. Most cases due to a recessive mutation of a gene called ABCA4. This causes a membrane protein used for active transport in retina cells to malfunction, as a result photoreceptive cells in the retina degenerate. These are the cells that detect light and so the vision becomes progressively worse.
We can now treat this by putting stem cells in the retina space and they will develop into retina cells.
What is Leukemia?
It is a type of cancer. It is a cancer of the white blood cells and involves the over production of them, no lump or tumour is produced, white blood cells are produced in the bone marrow, a soft tissue in the hollow centre of large bones such as the femur. They are then released into the blood.
To cure lukemia these over producing cells in the bone marrow must be killed perhaps with chemotherapy. But to remain healthy in the long term they will need to be able to produce white blood cells and so their white blood cells need to be replaced with stem cells.
You remove stem cell for somewhere in the body, usually the pelvis, then kill the cells in the bone mallow and then replace them with the stem cells.
Where are our three sources of stem cells?
- Embryonic stem cells, embryos can be deliberately created by fertilising egg cells with sperm and allowing the resulting zygote to develop for a few days until it has between four and sixteen cells.
- Cord blood stem cells - blood can be extracted from the umbilical chord of a new born baby. They can be frozen and used for later in the babies life.
- Adult stem cells - some adult tissues such as bone marrow.
Weight up the pros and cons of each way of getting stem cells?
EMBRYONIC STEM CELLS
- Ethical issues, can you create life just for our own use, it kills the embryo.
- Can differentiate into any type
- Unlimited growth potential
- Will be genetically different from adult and there is a greater chance of them becoming tumour cells.
CORD BLOOD CELLS
- Limited supply
- Limited capacity to differentiate, only really into blood cells
- Easily obtained and stored
- Does not kill embryo, is discarded anyway.
- Fully compatible with baby
ADULT STEM CELLS
- Difficult to obtain
- Limited supply
- Less growth potential
- Less chance of tumours and genetically the same.
- Limited capacity to differentiate
- Does not kill the adult.
