Essay on biology revision

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Pages: 10
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Patterns in Nature
CELL
What is cell theory?
Cell theory is a scientific theory which describes the properties of cells. Cells are the building blocks of which all living things are made. Cells are the smallest units of life.
Contribution of scientists to cell theory
Robert Hooke- the first person to see cells and name them. He was looking at a piece of cork and saw tiny boxes like the rooms and compartments.
Anton van Leeuwenhoek- used microscope and saw living microorganism swimming around in a drop of water.
Robert Brown- Brown was the first to discover and describe the nucleus inside plant cells.
Rudolf Virchow- where cell exists there must have been a preexisting cell
Evidence supporting the cell theory
1590- Hans and Zacharias constructed the first compound microscope using 2 lenses inside a tube.
1665- Robert Hooke observed cork with compound microscope
1676- Anton van Leeuwenhoek saw microorganisms under the microscope when he viewed a few drops of pond water.
1831- Robert Brown observed that the nucleus was present in both animal and plant cells.
1839- Matthias Schleiden and Theodor Schwann formulated the cell theory that all living matter is composed of small units called cells.
1858- Rudolf Virchow stated that where a cell exists there must have a pre-existing cell.
20th century- continued development of light microscopes and their uses
1933-present- Ernst Ruska built the first electron microscope
How has technology supported the development of the cell theory
Staining techniques- 1800s Joseph von Gerlach. Colour is produced by a variety of stains to create a contrast between the transparent material and its background. Heavy metals may be used to stain tissue for viewing under the electron microscope.
Light microscope- a light microscope passes a focus beam of light through the specimen. The specimen tested needs to be very thin so that the light can pass through. Improvements to the light microscope continued and in the 1870’s, oil immersion lenses were introduced by Zeiss and Abbe, enabling a good image up to 1500x magnification to be seen.
Electron microscope- the fine structure of the cell can only be viewed by using an electron microscope. The electron microscope was developed in the 1930’s and uses beam of electro instead of light as a source of energy.
Identify cell organelles that can be seen with light microscope and electron microscope
Organelle
Light microscope
Electron microscope
Cell membrane

Cell wall

Large vacuole

Mitochondria
Only with high power

Chloroplasts

Nucleus

Endoplasmic Reticulum

Ribosomes

Cells structure and organelles
CELL COMPONENT
DETAILS
PRESENT IN
VISIBLE

Name: Cell Membrane
Location: Surrounding the cell
Function: gives the cell shape & protection.
Regulates the movement of substances in and out of cell

Plant cells
Animal cells

Yes
Yes
Yes

Name: Ribosome
Location: Endoplasmic Reticulum
Function: Protein synthesis

Yes
Yes
Yes

Name: Mitochondria
Location: Cytoplasm
Function: Takes in nutrients, breaks them down and create energy rich molecules for the cell. It is called the cellular repiration.
Yes
Yes
Yes
Only in high magnification

Name: Golgi body
Location: near the endoplasmic reticulum near the cytoplasm
Functions: Final processing of food, liquids uses for storage and packaging
Yes
Yes
No

Name: Endoplasmic reticulum
Location: throughout the cytoplasm
Function: transport substances. Site of production of proteins. Rough: protein synthesis Smooth: lipid synthesis

Yes
Yes
No

Name: Chloroplast
Location: cytoplasm
Function: converts the light energy of sun into sugars that can be used by the cell.

Yes
No
Yes

Name: centrioles
Location: in the cytoplasm on the either side of the nucleus
Function: It helps the cell divide
Very rare
Yes
No

Name: cilia and flagella
Location: cell membrane
Function: help move the cell
Very rare
Yes
Very rare

Name: cell wall
Location:
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