A WebQuest for High School Biology

This Activity enable students to create a time line about the history and the beginning of life:

Click the link below to open the website for this activity.

The Cell Theory: A Historical Perspective

Tenets of Cell Theory (past - modern)

The Cell Theory

Ø All living things are made of cells.

Ø Cells are the basic units of life.

Ø Cells come only from other cells.

Types of cells:

Ø Prokaryotes - cells with no nucleus or organelles with membranes.
Bacteria and blue-green bacteria are prokaryotic cells.

Ø Eukaryotes - cells that contain a nucleus and organelles surrounded by a membrane.
The cells of protozoa, algae, fungi, plants, and animals are eukaryotic cells.

Classical interpretation of Cell Theory:

1. All organisms are made up of one or more cells.
2. Cells are the fundamental functional and structural unit of life.
3. All cells come from pre-existing cells.
4. The cell is the unit of structure, physiology, and organization in living things.
5. The cell retains a dual existence as a distinct entity and a building block in the construction of organisms.

Modern interpretation

The generally accepted parts of modern cell theory include:

1. The cell is the fundamental unit of structure and function in living things.
2. All cells come from pre-existing cells by division.
3. Energy flow (metabolism and biochemistry) occurs within cells.
4. Cells contain hereditary information (DNA) which is passed from cell to cell during cell division
5. All cells are basically the same in chemical composition.
6. All known living things are made up of cells.
7. Some organisms are unicellular, i.e., made up of only one cell.
8. Others are multicellular, composed of a number of cells.
9. The activity of an organism depends on the total activity of independent cells.

CELLS ARE THE STARTING POINT

CELLS ARE THE STARTING POINT

All living organisms on Earth are divided in pieces called cells. There are smaller pieces to cells that include proteins and organelles. There are also larger pieces called tissues and systems. Cells are small compartments that hold all of the biological equipment necessary to keep an organism alive and successful on Earth.

A main purpose of a cell is to organize. Cells hold a variety of pieces and each cell has a different set of functions. It is easier for an organism to grow and survive when cells are present. If you were only made of one cell, you would only be able to grow to a certain size. You don't find single cells that are as large as a cow. Also, if you were only one cell you couldn't have a nervous system, no muscles for movement, and using the internet would be out of the question. The trillions of cells in your body make your life possible.

One Name, Many Types

There are many types of cells. In biology class, you will usually work with plant-like cells and animal-like cells. We say animal-like because an animal type of cell could be anything from a tiny microorganism to a nerve cell in your brain. Plant cells are easier to identify because they have a protective structure called a cell wall made of cellulose. Plants have the wall; animals do not. Plants also have organelles like the chloroplast (the things that make them green) or large water-filled vacuoles.

We said that there are many types of cells. Cells are unique to each type of organism. Humans may have hundreds of types of cells. Some cells are used to carry oxygen (O₂) through the blood (red blood cells) and others might be specific to the heart. If you look at very simple organisms, you will discover cells that have no defined nucleus (prokaryotes) and other cells that have hundreds of nuclei (multinucleated). The thing they all have in common is that they are compartments surrounded by some type of membrane.

cells

Plant cell

The cell is the basic unit of life. Plant cells (unlike animal cells) are surrounded by a thick, rigid cell wall.

The following is a glossary of plant cell anatomy terms.

amyloplast - an organelle in some plant cells that stores starch. Amyloplasts are found in starchy plants like tubers and fruits.

ATP - ATP is short for adenosine triphosphate; it is a high-energy molecule used for energy storage by organisms. In plant cells, ATP is produced in the cristae of mitochondria and chloroplasts.

cell membrane - the thin layer of protein and fat that surrounds the cell, but is inside the cell wall. The cell membrane is semipermeable, allowing some substances to pass into the cell and blocking others.

cell wall - a thick, rigid membrane that surrounds a plant cell. This layer of cellulose fiber gives the cell most of its support and structure. The cell wall also bonds with other cell walls to form the structure of the plant.

centrosome - (also called the "microtubule organizing center") a small body located near the nucleus - it has a dense center and radiating tubules. The centrosomes is where microtubules are made. During cell division (mitosis), the centrosome divides and the two parts move to opposite sides of the dividing cell. Unlike the centrosomes in animal cells, plant cell centrosomes do not have centrioles.

chlorophyll - chlorophyll is a molecule that can use light energy from sunlight to turn water and carbon dioxide gas into sugar and oxygen (this process is called photosynthesis). Chlorophyll is magnesium based and is usually green.
chloroplast - an elongated or disc-shaped organelle containing chlorophyll. Photosynthesis (in which energy from sunlight is converted into chemical energy - food) takes place in the chloroplasts.

christae - (singular crista) the multiply-folded inner membrane of a cell's mitochondrion that are finger-like projections. The walls of the cristae are the site of the cell's energy production (it is where ATP is generated).

cytoplasm - the jellylike material outside the cell nucleus in which the organelles are located.
Golgi body - (also called the golgi apparatus or golgi complex) a flattened, layered, sac-like organelle that looks like a stack of pancakes and is located near the nucleus. The golgi body packages proteins and carbohydrates into membrane-bound vesicles for "export" from the cell.

granum - (plural grana) A stack of thylakoid disks within the chloroplast is called a granum.
mitochondrion - spherical to rod-shaped organelles with a double membrane. The inner membrane is infolded many times, forming a series of projections (called cristae). The mitochondrion converts the energy stored in glucose into ATP (adenosine triphosphate) for the cell.

nuclear membrane - the membrane that surrounds the nucleus.
nucleolus - an organelle within the nucleus - it is where ribosomal RNA is produced.

nucleus - spherical body containing many organelles, including the nucleolus. The nucleus controls many of the functions of the cell (by controlling protein synthesis) and contains DNA (in chromosomes). The nucleus is surrounded by the nuclear membrane

photosynthesis - a process in which plants convert sunlight, water, and carbon dioxide into food energy (sugars and starches), oxygen and water. Chlorophyll or closely-related pigments (substances that color the plant) are essential to the photosynthetic process.
ribosome - small organelles composed of RNA-rich cytoplasmic granules that are sites of protein synthesis.

rough endoplasmic reticulum - (rough ER) a vast system of interconnected, membranous, infolded and convoluted sacks that are located in the cell's cytoplasm (the ER is continuous with the outer nuclear membrane). Rough ER is covered with ribosomes that give it a rough appearance. Rough ER transport materials through the cell and produces proteins in sacks called cisternae (which are sent to the Golgi body, or inserted into the cell membrane).

smooth endoplasmic reticulum - (smooth ER) a vast system of interconnected, membranous, infolded and convoluted tubes that are located in the cell's cytoplasm (the ER is continuous with the outer nuclear membrane). The space within the ER is called the ER lumen. Smooth ER transport materials through the cell. It contains enzymes and produces and digests lipids (fats) and membrane proteins; smooth ER buds off from rough ER, moving the newly-made proteins and lipids to the Golgi body and membranes

stroma - part of the chloroplasts in plant cells, located within the inner membrane of chloroplasts, between the grana.

thylakoid disk - thylakoid disks are disk-shaped membrane structures in chloroplasts that contain chlorophyll. Chloroplasts are made up of stacks of thylakoid disks; a stack of thylakoid disks is called a granum. Photosynthesis (the production of ATP molecules from sunlight) takes place on thylakoid disks.

vacuole - a large, membrane-bound space within a plant cell that is filled with fluid. Most plant cells have a single vacuole that takes up much of the cell. It helps maintain the shape of the cell.

Animal Cell

The cell is the basic unit of life. All organisms are made up of cells (or in some cases, a single cell). Most cells are very small; most are invisible without using a microscope. Cells are covered by a cell membrane and come in many different shapes. The contents of a cell are called the protoplasm.

The following is a glossary of animal cell terms:

cell membrane - the thin layer of protein and fat that surrounds the cell. The cell membrane is semipermeable, allowing some substances to pass into the cell and blocking others.

centrosome - (also called the "microtubule organizing center") a small body located near the nucleus - it has a dense center and radiating tubules. The centrosomes is where microtubules are made. During cell division (mitosis), the centrosome divides and the two parts move to opposite sides of the dividing cell. The centriole is the dense center of the centrosome.

cytoplasm - the jellylike material outside the cell nucleus in which the organelles are located.
Golgi body - (also called the Golgi apparatus or golgi complex) a flattened, layered, sac-like organelle that looks like a stack of pancakes and is located near the nucleus. It produces the membranes that surround the lysosomes. The Golgi body packages proteins and carbohydrates into membrane-bound vesicles for "export" from the cell.

lysosome - (also called cell vesicles) round organelles surrounded by a membrane and containing digestive enzymes. This is where the digestion of cell nutrients takes place.
mitochondrion - spherical to rod-shaped organelles with a double membrane. The inner membrane is infolded many times, forming a series of projections (called cristae). The mitochondrion converts the energy stored in glucose into ATP (adenosine triphosphate) for the cell.