Cell Membrane example essay topic

SECTION 3.1 WHERE LIFE HAPPENS 1. Living things can be either uni-cellular (one cell) or multi cellular. A bacteria is one type of unicellular. 2.

About 8000 of the smallest bacteria could fit inside one of your red blood cells. 3. The longest cells are the thin nerve cells found in large animals and they can be more than a meter long. 4. The cell with the greatest volume is an unfertilized ostrich egg 5.

A cell's shape is related to its function. For example, a long nerve cell is long and it carries messages from your spine to your toes. The contraction and relaxation of muscle tissue is responsible for the movement in animals. A SMALL NEW WORLD 1. In the 1600's people only knew about organisms they could see with the unaided eye. 2.

A trio of Dutch eyeglass makers invented the microscope in the late 1500's. It consisted of a tube with lenses ground from rock crystal, and it magnified objects up to 9 times their actual size. 3. In 1665 the British scientist Robert Hooke published a set of drawings illustrating what he had observed with a microscope. 4.

In the early 1670's Anton van Leeuwenhoek, a Dutch fabric-store owner, began to grind lenses as a hobby. He used handheld microscopes to examine materials such as pond water and blood. BIOLOGISTS BUILD A THEORY 1. By the 1830's many biologists were using the microscope as their chief investigative tool 2. Mathias Schleiden was a botanist, a scientist that studies plants.

He found that plant parts he examined were made out of cells. In 1838 Schleiden made the generalization that all plants are made of cells. 3. Theodor Schwann was studying and animals. His microscopic investigations of animal parts led him to generalize that all animals were made of cells. 4.

In 1858, a German doctor named Rudolf Virchow disputed the idea of spontaneous generation. Virchow reasoned that new plant cells arise only from existing plant cells, and new plant animal cells arise only from existing animal cells. 5. The cell theory consists of three principles: Cells are the basic units of all life. All organisms are made of one or more cells. All cells arise from the existing cells.

SEEING SMALLER 1. One of the most important tools used by biologists is the microscope. 2. Until the 1950's microscopes were light microscopes-instruments that use either sunlight or artificial light to view objects. With the advantage of this it can magnify many microscopic objects while they are alive. 3.

Light microscopes can magnify objects such as tiny organisms up to about 1000 times their actual size. If a larger magnification is tried then it will distort the image. 4. One way to increase the contrast is using dyes to stain or color a specimen.

Dyes improve contrast by selectively staining certain parts of the specimen. The stained are becomes more visible, but it tends to kill the specimen. 5. Another way to increase contrast is by manipulating light. 6. Since the 1950's biologists have been using electrons instead of light.

Electron microscopes can magnify objects up to a million times their actual size. However, before a specimen can be viewed the microscope must be tuned up. They work in two ways to produce images. Some pass electrons through the specimen and others scan the organism. 7.

There is a new microscopic technique that has been recently developed. It uses some of the principles of the light microscope, but has the potential to allow imaging of single atoms. SECTION 3.2 CONTROLLING THE FLOW 1. The cells of all organisms are surrounded by a cell membrane. The cell membrane is a thin layer of lipid and protein that separates the cell's contents from its environment.

It controls whatever enters or leaves the cell. 2. Membranes are made up of mostly of and that is a type of lipid made from glycerol, two fatty acids and a phosphate group. 3. The two ends of the molecule have different properties in water. The phosphate head of a is hydrophilic meaning water loving.

The phosphate head dissolves easily in the water. The lipid tails of the molecule are hydrophobic meaning water fearing, so the lipid tails do not dissolve in water. 4. When dropped in water, phospholipids will form two layers, called a lipid bi layer. The phosphate heads on both sides of the bi layer face the water.

The lipid tails of each layer will face each other. 5. The phospholipids in the cell membrane are constantly being formed and broken down by chemical reactions in living cells. 6. Protein molecules are embedded in the lipid bi layer and about 30% of the proteins attached to one side of the membrane.

Some of these proteins help move materials in and out of the cell. INSIDE THE GREAT MEMBRANE 1. The cytoplasm is a semifluid substance made primarily of water and organic compounds. Various structures called organelles are located in the cytoplasm. 2. The is a network of protein fibers and tubes extending throughout the cytoplasm.

The network gives the cell support and helps it to maintain or change its shape. 3. Materials are transported throughout the cell on the. Also the enables the cell itself to move. CHROMOSOME KEEPER 1. The nucleus contains most of the cell's genetic material.

A double membrane called the nuclear envelope surrounds it. 2. Like the outer membrane of a cell, each membrane of the nuclear envelope is a lipid bi layer. Together the two membranes separate the nucleus from the cytoplasm.

3. A cell's genetic information is kept in structures called chromosomes. The nucleic acid in the chromosomes carries the genetic information. 4. Another identifying structure of the nucleus is the nucleolus and there are ribosomes found there.

Ribosomes help make proteins. NUCLEUS OR NOT? 1. Organisms whose cells that have no definite nucleus are called prokaryotes. 2.

Organisms whose cells have a nucleus surrounded by a nuclear membrane called eukaryotes. 3. Most prokaryotic cells are tiny-about one tenth the width and one thousandth the volume of eukaryotic..