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Light Microscope and Electron Microscope Comparison

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Light Microscope

Electron Microscope (EM)

How it works

The stage of the microscope holds slides containing specimens. You can adjust the stage adding further light or move it allowing different layers of the object to be in focus. The user then looks through the microscope eyepiece, where amirrorat the bottom of the microscope redirects light rays reflecting the object through a hole in the stage, magnifying the image. Both dead and live specimens can be seen. Preparation is simple and can take a few minutes to hours.

A high-voltage electricity supply powers the cathode.

This produces a beam of electrons. An electromagnetic coil focuses the electrons into a more powerful beam.

Another electromagnetic coil focuses the beam onto a certain part of the specimen which produces an image of it, which is magnified.

The image can be viewed directly or on a TV monitor which is attached to an image intensifier. Only dead or dried specimens can be seen. Preparation time is more complex and can take a few days.

Uses

Schools, colleges and universities

Medical Facilities and Laboratories

Resolution

Low resolution power, due to the wavelength of light, can cause low clarity.

High resolution power leading to high clarity.

Magnification

Usually between 500x to 1500x

Direct magnification of up to 160,000x and photographic magnification of 1000,000x plus

2b)

Organelle

Function of Organelle

Chromatin

In a cell, chromosomes are compressed into the nucleus as chromatin.

The main function of chromatin is:

  • to compress DNA to fit in the cell,
  • to strengthen DNA to permit mitosis,
  • to avoid DNA damage,
  • to control gene expression and DNA replication.

Lysosome

The Main function of lysosome is to break down waste materials and worn out organelle

Lysosome contains acid hydrolase enzymes. Once unwanted waste is inside the cell, the lysosome attaches itself to the waste material and releases their enzymes. The enzymes break down the molecules ready for excretion.

Nucleus

The Nucleus of a cell is the control point for gene expression and the replication of DNA. The Nucleus also controls the hereditary characteristics of an organism. it stores chromatin, proteins and RNA.

Mitochondria

The main function of Mitochondria is to convert energy into forms that are usable by the cell through cellular respiration.

Flagella

The flagellum has two functions. Its structure allows it to assist movement and to test the temperatures and chemical balances in their environment.

Giolgi Appartus

The main function is to carry out processing of proteins generated in the endoplasmic reticulum.

This is completed by breaking down proteins into small, active fragments.

As well as directing lipids within cells and production of lysosomes, carbohydrates and proteins, needed by the body, to their proper destination.

Ribsome

The main function is to assemble amino acids to create specific proteins, which are essential for carrying out the cell's activities. This is known as protein syntheses. During Protein Synthese, Ribsomes reads the code represented by RNA, from the cells main DNA, allowing synthese to occur. All new proteins are formed from the ribsomes.

Smooth Endoplasmic

Has a wide variety of functions:

  • carbohydrate and lipid synthesis.
  • Transports Endoplasmic Reticulum
  • products to specific destinations, both produced in the smooth Endoplasmic and rough Endoplasmic.
  • Produces emxymes in the liver that helps removes certain compounds
  • aids in the contraction of muscle cells
  • In the brain cell it combines male and female hormones
  • The rough Endoplasmic is usually interconnected to Smooth endoplasmic and the proteins and membranes made by the rough ER move into the smooth ER to be transferred to other locations.

Rough Endoplasmic

Has a wide variety of functions:

  • Manufactures membranes and secretion of proteins.
  • In some white blood cells it produces antibodies.
  • In pancreatic cells, the rough ER produces insulin.

2C)

The main function of Erthrocytes is the transportation of oxygen to the bodies cells and tissues and expulsion of carbon monoxide to the lungs. Its bi-concave shape increases the surface area which increases the speed of diffusion, enabling it to receive and release oxygen more effectively. Their small size and ability to change shape helps them fit through the various blood vessels, all of these structures aid Erthocytes to complete their function.

The function of Spematozoa is to fertilise a female ovum during/after sexual intercourse. A pointed tip in the head of the sperm allows it to effectively enter the ovum. The middle of the sperm, is very short and after ejaculation, it releases mitchondria to give the spermatozoa bursts of energy. The tail, moves the sperm by using whip-like, movements, allowing speed/movement necessary due to it's.short life span. If a sperm is successful in reaching an ovum, the cell divides, disposing of the tail. All of these structures aid Spermatozoa to try and complete their purpose.

Cilliated epithelial cells are tiny hair like structures on the surface of a cell, their function is for transportation. The structure allows the hairs to produce a synchronised swaying motion, transporting fluids or unwanted particles such as mucus to the back of the throat to be disposed of.

TAQ 3)

Cell membranes consist of a Phospholipid Bilayer, this forms the initial shield of the cell. Due to the various components of a membrane they are referred to as mosaic. Within the Bilayer there are both lipids and proteins. At body temperature, Phosolipids have a consistency of an oil like substance that allows plasma membranes to be flexible and fluid. They can attach and detach to cells. Phosolipids have a hydrophillic head and a hydrophobic tail and in each cell the head forms the outer layer of the membrane, while the tail is wedged in-between the cell to form the bilayer. Intrinsic proteins, cover the complete span of the Bilayer and Extrinsic proteins are partial embedded within the bilayer. Cholesterol lipids also help strengthen the bilayer, while regulating the activity of some integral proteins. Therefore, it can correctly be said that a cell membrane is a fluid mosaic model made up of lipids and proteins molecules.

4) Active transport of molecules is when carrier proteins transport specific dissolved molecules from a lower concentration to a higher concentration through the cell membrane.

Diffusion is when feely moving molecules spread from an area of high concentration to an area of low concentration through the cell membrane.

Osmosis is the transportation of water through the permeable membrane, from a level of high concentration solution to a low concentration solution.

 

Active transportation

Diffusion

Osmosis

Use of energy

Yes – The use of transportation proteins require the use of cellular energy, normally ATP to actively pump substances into or out of the cell.

No— Does not require cellular energy. Uses kinetic energy which provides heat which enables the continuous movement of the molecules.

No – uses kenetic energy.

Gradient

Moves from an area of lower to a higher concentration.

Moves from an area of high concentration to a low concentration

Moves from a less concentrated solution to a more concentrated solution.

Is the transportation assisted?

Assisted by carrier proteins, which contains ions and nutrients. These proteins, bind themselves to the molecule transporting them across the epithelial layers. They would otherwise be blocked and unable to enter the cell.

Emzymes provide a chemical pump using ATP which provides energy for the carrier proteins.

Only facilitated diffusion through the help of ion channel proteins and carrier proteins.

No – solute spreads out and doesn’t require assistance as it is water based.

Example of when it can occur?

During Digestion - Carbohydrates are broken down into glucose, which is absorbed and actively transport into the bloodstream and taken around the body.

During Respiration - oxygen diffuses across the alveolar walls into the blood, which is picked up by red blood cells and distributed around the body.

In the cell - Water molecules pass from the pure water into the dilute solution than back through the permeable membrane, until there is an even concentration of water, and the system is in equilibrium.

5)

Type of tissue

Describe how the structure of the tissue is linked to function

Nerve Tissue

Nervous tissue is responsible for sensing stimuli and transmitting signs to and from different parts of an organism.

Nerve tissue consists of two main types of cells: Neurone and neuroglia.

Each neurone consists of perikaryon which contains the nucleus of the cell. They have dendrites that extend away from the cell body receiving nerve impulses.

Neuroglia functions depend on the specific type of neuroglia. For example Astrogilia, are star-shaped cell and extends from the cell body into the surrounding network of nerve fibres. Its main purpose is that of transportation, Supply of nutrients to neurons. Neuroglia does not receive nerve impulses.

Muscle Tissue

There are three types of muscle tissues: Skeletal, Cardiac and Smooth Muscle Tissue.

Skeletal Muscle cells are long and cylindrical in shape. It consists of layers of Epimysium, which protects the muscle from friction, connects the muscle to muscle tendons. This makes it possible for people to flex and move their skeleton.

Cardiac Muscle, is the heart. Cardiac muscle like skeletal muscle is striated. The cells are short, branched and interconnected and contains a nucleus. The ends are interconnected which allows signals to be transmitted, for example, if a person is nervous, signals are transmitted which can speed up the heart rate.

Smooth Muscle Tissue contains myofibrils which are randomly placed unlike other muscle tissues which are strategically placed. It is located in the walls of organs and is responsible for digestion through peristalisi, constriction of blood vessels etc

Connective Tissues

Connects different types of tissue to each other. They are various types for example: Dense Connective Tissue, which is very strong and connects muscle to bones, it consists of cells, which are organised in one direction so that pulls allowing for example a knee to flex. It is made up of parallel collagen fibers, some elastic fibers and fibroblast.

Loose Connective tissue - Adipose tissue which is a fatty tissue and protects organs and aids in maintaining body temperature. Found mainly in the breasts and under the skin.

Epithelial tissues

Covers a body surface or lines a body cavity for example: The lining of the mouth, lung alveoli and kidney tubules all are made of epithelial tissue. It is supported by a layer of connective tissue. Its function is to protect cells and tissues underneath and therefore it is solid with no intercellular space.

6)

The main function of the heart is to pump blood and oxygen around the body. The mass portion of the heart is made up of Cardiac muscle which pumps the heart, making it beat to circulate the blood flow. It also contains nervous tissue which stimulates the heart through electrical impulses to make it contract. Epithelium tissues supplies the heart muscle with oxygen and nutrients mainly supplied by blood vessels and contains fatty tissue which protects the heart, as well as offers an emergency supply of energy if needed.

The main function of the lungs is to transport oxygen into the bloodstream, and to dispose of carbon dioxide from the bloodstream.The lungs are two sacs, which expands with air when a person inhales and deflates when a person exhales. The most common types of tissues found within the lungs are stratified squamous, simple cuboida and Pseudostratified columnar.

Both the heart and the lungs interact and play a crucial role in the respiration and cardiovascular system. During respiration, oxygenated blood, which is inhaled from the lungs is passively diffused to the heart which then pumps it out to the rest of the body. It is absorbed into tissues and cells. De-oxygenated blood returns to the heart, after which it is sent back to the lungs to get further oxygen and to release carbon dioxide through exhaling. Due to the lungs tissues being thin, it allows easier diffusion to the blood and therefore smoother respiration. Although the cardiovascular system mainly involves the heart and blood , as oxygen from the lungs is transported via the blood stream, both organs also play a vital roles within it, in order to maintain life.

References

Websites

BBC. (2014). Cells. Available: http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/cells/cells3.shtml. Last accessed 28th sep 2014

Ningthoujam Sandhyarani. (2012). Ribosomes Function. Available: http://www.buzzle.com/articles/ribosomes-function.html. Last accessed 24th sep 2014.

Shashank Nakate. (2013). Golgi Apparatus Function. Available: http://www.buzzle.com/articles/golgi-apparatus-function.html. Last accessed 24th sep 2014.

wise geek health . (2014). What Is the Normal Size of Red Blood Cells?. Available: http://www.wisegeekhealth.com/what-is-the-normal-size-of-red-blood-cells.htm. Last accessed 24th sep 2014.

Books

Alberts B, Bray D, Lewis J, Raff M, Roberts K, Watson JD (1994). Molecular Biology of The Cell. 3rd ed. New York: Garland Publishing. p 4 -39, p 89-98, p139-141, p223, p195-196, p508-523, p655,

Kratz R, Siegfried D (2010). Biology for Dummies. 2nd ed. Indiana: Wiley. p47-63, p277-293, p221-239, p81-82


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