Showing posts with label Biology 11 University. Show all posts
Showing posts with label Biology 11 University. Show all posts
Monday, February 7, 2011
1.2 Apoptosis: Cell Suicide
1) What are the two common causes of cell death?
- mechanical forces or toxic chemicals
- eliminate cells harmful to the organism
2) Describe the changes that occur during apoptosis.
- shrinking
- disintegration of mitochondria and nucleus
- breakdown of the cell into several membrane-bound fragments
- intake of cell fragments by other cells
3) Describe the three triggers of apoptosis.
- The formation of protein clusters called apoptosomes within the cell.
- The attaching of cell death activator molecules to the outer surface of the cell membrane.
- The formation of reactive oxygen molecules such as hydrogen peroxide in the cell.
4) Why do researchers assume that apoptosis is responsible for the decrease in the number of T-helper cells in AIDS?
When the T-helper cells are infected with HIV, they die by apoptosis.
5) Most cancer drugs used today attempt to slow down the rate of cell division (mitosis). Using the internet and other resources, discover how research on apoptosis might be used to produce new cancer drugs.
Cells commit apoptosis by disintegrating its organelles. This could help scientist because it they can find a way to target specific cells that are considered cancerous and duplicate their apoptosis process to rid the body of an excess amount of mutated cells.
Why should we learn about cells?
- Protects cells to prevent infection and other harmful effects
- Observe cells to diagnose diseases
- Treat cells to heal illness
- Stop harming cells through our choices and actions
Types of cells:
Eukaryotes (true cells):
- cells with a nuclear membrane surrounding the nucleic acid
- e.g. plant and animal cell
Prokaryotes:
- Cells with no nuclear membrane
- e.g. bacteria and cyanobacteria (blue-green)
By breaking an intermolecular bond, you create a different state of matter (e.g. two water molecules broken apart by heat would create water vapor).
The DNA in a bacteria is called a Plasmid. Viruses don't have the ability to reproduce itself therefore is not considered a cell. They reproduce by injecting DNA into a host cell which then explodes - killing the host cell - releasing all new born viruses.
Incubation period: time for a virus to reproduce (e.g. when you're contagious)
The most contagious time is usually before symptoms start to show.
The functions of a cell:
- to grow
- to repair and heal
- to go through cell division and reproduce
For one cell birth there has to be one cell death. Older cells make more mistakes which is why older people have more diseases.
Do cells live forever?
- No, after a certain number of cell divisions all cells die by committing suicide (apoptosis).
When a cell is not functioning properly and cannot be fixed, the cell releases the enzymes in the lysosome to sacrifice itself for the overall health of the organism. It disintegrates all organelles within the cell.
- Cells also die by injury caused by mechanical forces or toxic chemicals.
Reasons for apoptosis:
- To eliminate cells that threaten the overall health of a multicellular organism
- Part of normal development
Plant cells have very defined, boxy shapes because of the cell wall. The cell wall is made of cellulose. Glucose helps you absorb waste much easier. Vacuoles in plant cells are very large to store water, nutrients, etc.
Cytoplasm: water, any other fluid, waste, etc. inside of the cell wall.
Turgor Pressure: when the fluids push up against the cell wall to keep it up-right so it doesn't wilt.
Mitochondria: turns everything into a usable source of energy.
Ribosomes are not membrane bound and carry protein. They sit on top of the endoplasmic reticulum. They just store energy and are the smallest organelle in a cell. The endoplasmic reticulum with ribosomes on top make it "rough".
Chloroplast gives plants its colour.
RNA: ribonucleic acid. (inside nucleolus)
DNA has to be protected at all times. (deoxyribonucleic acid)
mRNA: messenger inside the nucleolus that tells the cell to produce proteins. It's a strand of code.
rRNA: comes to translate and read the code, calls out tRNA.
tRNA: carries a specific amino acid to come hook up the message. It's like a taxi, it picks up the amino acid, drops it off, then goes to get another one.
Our body can have up to 20 amino acids. 12 are produced by our bodies and 8 come from our diets.
Only animal cells have lysosomes and centrioles. Double layers are all membrane bound.
Microscopes
Use a microscope to:
- study chemical reactions
- how a cell works
- study cells
- see organelles
- see DNA replicate
Insulin is used to re-harvest genes. Sophisticated microscopes are used.
Biopsy: a sample of a tumor looked at under a microscope.
Tissues: multiple cells put together.
Oil immersion lens is used specifically to look at a specimen with a drop of oil on it to give a very high resolution magnification. Field of view changes with your change of magnification.
You can move the stage up, down and sideways.
The diaphragm controls the amount of light. Only use lens paper to clean the lens.
Tissues put together make organs, organs put together make systems. Skin is the largest organ, second largest is the liver.
Chapter One: Cell Biology
1938, James Hillier and Albert Prebus at U of T produced the first functional electron microscope. Scientists able to view viruses and sub cellular parts with great resolution. Viruses are measured in microbes.
Resin: solidified cube of a cell.
The three types of Microscopes:
1) Transmission Electron Microscope (TEM)
- Beam of electron passes through very thin slices of specimen
- Two dimensional view
- Time consuming to prepare specimen
- View dead specimen only
- Not portable
2) Scanning Electron Microscope (SEM)
- Electron scans across the surface of the sample
- Secondary electron releases by the sample to form a 3-D image
3) Scanning Tunneling Microscope (STM)
- A minuscule electron probe is placed near the sample
- The created image is converted to a topographic image by the computer
- Can manipulate molecules and atoms
- Study biology at the atomic level
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