The Cell Overview
Objectives
List the scientists who contributed to our knowledge of the cell
List the 3 components of the cell theory
Compare prokaryote to eukaryote cells
Label a plant and animal cell
Know the functions of all cell organelles
Early Contributions
Robert Hooke - The first person to see cells, he was looking at cork and noted that he saw "a great many boxes. (1665)
Anton van Leeuwenhock - Observed living cells in pond water, which he called "animalcules" (1673)
Theodore Schwann - zoologist who observed that the tissues of animals had cells (1839)
Mattias Schleiden - botonist, observed that the tissues of plants contained cells (1845)
Rudolf Virchow - also reported that every living thing is made of up vital units, known as cells. He also predicted that cells come from other cells. (1850 )
The Cell Theory
1. Every living organism is made of one or more cellss.
2. The cell is the basic unit of structure and function.
3. All cells arise from pre-existing cells.
*Why is the Cell Theory called a Theory and not a Fact?
Cell Features
Ribosomes - make protein for use by the organismCytoplasm - jelly-like goo on the inside of the cell
DNA - genetic material
Cytoskeleton - the internal framework of the cell
Cell membrane - outer boundary of the cell, some stuff can cross the cell membrane.
Types of Cells
Prokaryotic Cells
Prokaryotes are very simple cells, probably first to inhabit the earth.
Prokaryotic cells do not contain a membrane bound nucleus.
Bacteria are prokaryotes.
DNA of bacteria is circular.
The word "prokaryote" means "before the nucleus"
Other features found in some bacteria:
Flagella - used for movement
Pilus - small hairlike structures used for attaching to other cells
Capsule - tough outer layer that protects bacteria, often associated with harmful bacteria
Eukaryotic Cells
Eukaryotic cells are more advanced cells. These cells are found in plants, animals, and protists (small unicellular "animalcules").
The eukaryotic cell is composed of 4 main parts:
cell membrane - outer boundary of the cell
cytoplasm - jelly-like fluid interior of the cell
nucleus - the "control center" of the cell, contains the cell's DNA (chromosomes)
organelles - "little organs" that carry out cell functions
Cell Structures
The Nucleus
- Usually found at center of cell
- Has a nuclear membrane ;nuclear pores
-
Contains cell's DNA in one of 2 forms
- chromatin- DNA bound to protein (non-dividing cell)
- chromosomes- condesed structures seen in dividing cell
- Also contains an organelle called nucleolus - which makes the cell’s ribosomes
Mitochondria
Energy center or "powerhouse" of the cell. Turns food into useable energy (ATP)
Ribosome - make protein, located on the rough endoplasmic reticulum and throughout the cytoplasm
Golgi Apparatus - processing, packages and secretes proteins; proteins are transported in vesicles
Lysosome - contains digestive enzymes that can break things down, also called a "suicide sac" because the rupturing of the lysosome will cause the cell to destroy itself
Endoplasmic Reticulum - Transport, "intracellular highway". Ribosomes are positioned along the rough ER, protein made by the ribosomes enter the ER for transport.
Smooth ER - no ribosomes
Rough ER - contains ribosomes
Cytoskeleton - helps maintain the cells shape; supports the cell and aids in cell movement\
microtubules / microfilaments / centrioles
microtubules are used to build cilia and flagella
Vacuole - storage area for water and other substances, plant cells usually have a large central vacuole
Protein Production
The cell is like a factory. Its product is protein which goes to body to serve different functions.
- DNA has instructions to build; protein
- These instructions are sent to ribosomes
- The ribosomes build protein and send it through ER
- The proteins are delivered to& golgi where they are completed and tagged for export outside the cell
Plant Cell
Has all the components of animal cells with some additional structures.
Chloroplast - Uses sunlight to create food, photosynthesis (only found in plant cells), contains green pigment chlorophyll
Cell Wall - outside the cell membrane of plants and some bacteria, the cell wall serves as support
Central vacuole - large water container, helps maintain a turgor (stiffness) in the plant
Animal Cell versus Plant Cell
ORGANELLES WITH DNA
- The Mitochondria and Chloroplasts have their own DNA
- ENDOSYMBIOSIS THEORY - eukaryotic cells evolved from the engulfing of bacteria cells, thus creating additional cell parts
CELL MEMBRANE
- Function: to regulate what comes into the cell and what goes out
- Composed of a double layer of phospholipids and proteins
| CELL STRUCTURE | LOCATION | DESCRIPTION | FUNCTION |
|
Cell Wall |
Plant, Fungi, & Bacteria, but not animal cells |
|
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Cell Membrane |
All cells |
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Nucleus |
All cells except prokaryotes |
|
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Nuclear membrane |
|
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Cytoplasm |
All cells |
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Endoplasmic reticulum (ER)  |
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Ribosome |
All cells |
|
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Mitochondrion |
All cells except prokaryotes |
|
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Vacuole |
Plant cells have a single, large vacuole |
|
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Lysosome |
Plant - uncommon |
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Chloroplast
|
Plants and algae |
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nucleolus |
All cells except prokaryotes |
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Golgi Apparatus |
All cells except prokaryotes |
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Cilia |
Animal cells, Protozoans |
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Flagellum |
Bacterial cells & Protozoans |
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Centrioles |
Animal cells |
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Cytoskeleton |
All cells |
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Cells |
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Animal Cell Coloring
I. Directions: Color each part of the cell its designated color.
Cell Membrane(light brown) |
Nucleolus (black) |
Mitochondria (orange) |
|
Cytoplasm (light yellow) |
Golgi Apparatus (pink) |
Lysosome (purple) |
|
Nucleoplasm (pink) |
Flagella (red/blue striped) |
Microtubules (dark green) |
|
Nuclear Membrane(dark brown) |
Rough Endoplasmic Reticulum (dark blue) |
Ribosome (red) |
|
Smooth Endoplasmic Reticulum( light blue) |
II. Briefly describe the function of the cell parts.
1. Cell membrane ______________________________________________
2. Endoplasmic Reticulum _________________________________________
3. Ribosome ____________________________________________________
4. Golgi Apparatus ____________________________________________________
5. Lysosome ____________________________________________________
6. Microtubule ____________________________________________________
7. Mitochondria ____________________________________________________
8. Nucleus ____________________________________________________
Plant Cell Coloring
|
Cell Membrane (orange) Nucleoplasm (yellow) Mitochondria (red) Vacuole (lt. Blue) Chromatin (gray) |
Cell Wall (dark green) Nucleolus (brown) Chloroplasts (light green) |
|
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Smooth Endoplasmic Reticulum (pink) Rough Endoplasmic Reticulum (pink) |
||
Analysis
1. Name two things found in a plant cell that are not found in an animal cell:
2. How does the shape of a plant cell differ from that of an animal cell?
3. What is the function of the chloroplasts?
4. What is the function of the vacuole?
Cell City Analogy
In a far away city called Grant City, the main export and production product is the steel widget. Everyone in the town has something to do with steel widget making and the entire town is designed to build and export widgets. The town hall has the instructions for widget making, widgets come in all shapes and sizes and any citizen of Grant can get the instructions and begin making their own widgets. Widgets are generally produced in small shops around the city, these small shops can be built by the carpenter's union (whose headquarters are in town hall).
After the widget is constructed, they are placed on special carts which can deliver the widget anywhere in the city. In order for a widget to be exported, the carts take the widget to the postal office, where the widgets are packaged and labeled for export. Sometimes widgets don't turn out right, and the "rejects" are sent to the scrap yard where they are broken down for parts or destroyed altogether. The town powers the widget shops and carts from a hydraulic dam that is in the city. The entire city is enclosed by a large wooden fence, only the postal trucks (and citizens with proper passports) are allowed outside the city.
Match the parts of the city (underlined) with the parts of the cell.
1. Mitochondria _______________________________________________
2. Ribosomes ________________________________________________
3. Nucleus ________________________________________________
4. Endoplasmic Reticulum ________________________________________________
5. Golgi Apparatus ________________________________________________
6. Protein ________________________________________________
7. Cell Membrane ________________________________________________
8. Lysosomes ________________________________________________
9. Nucelolus ________________________________________________
** Create your own analogy of the cell using a different model. Some ideas might be: a school, a house, a factory, or anything you can imagine**
Cell Project
Purpose: The purpose of this project is to make a 3D model of a cell in order to better understand the parts and workings of a cell.
Using household items make a three-dimensional model of a plant or animal cell that meets the criteria listed below. (Sample items: cereal, balloons, gummi worms, mints, fruit slices, dried fruit, matches, gum balls, peanuts, rope licorice, jelly beans, sesame seeds, other candies, toothpicks. Craft packages also may work: clay, beads, pipecleaners..etc)
Choose what type of cell you will build, a typical plant or animal cell. Include this label somewhere on your model.
Create a KEY or label in some way each part on your model and its function.
| Cell Project Rubric | ||||
| Category | Scoring Criteria | Excellent (3 pts) | Satisfactory (2 pts) | Minimal (1 pt) |
| Craftsmanship | Model is creative, shows effort | |||
| The model is 3 dimensional | ||||
| Model stays together, not too messy or difficult to move around | ||||
| Cell Parts | Key, legend, or labeling is easy to use to identify parts on the model | |||
| Functions of cell parts included (accurate) | ||||
| Appropriate material is used so that it looks like the cell part it is modeling | ||||
| Parts of organized within the cell in their appropriate places | ||||
| Written Word | Basic grammar, spelling on key and any other writing used in model | |||
Samples:
Do you have photos of cell models? I would love to include them in my gallery!
The Cell Study Guide
View the full size Free Cell Study Guide.
The Cell
The cell is possibly the most important concept in biology since it is the basic unit of life. Every living organism is made up of cells (or just one in the case of bacteria). Your body is composed of microsopic cells that are only visible if viewed under a microsocope. All the animals, trees and plants are made up of cells that share many similar characteristics. They all have cell membranes separating them from the outside environment, DNA to store information, RNA to pass this information to the ribosome- and ultimately protein that is translated from the RNA (mRNA to be specific). These common features make it possible to learn clues about how our own cells function by studying the cells of other model organisms like mice, fruit flies or nematodes. Most organisms that we are used to seeing are multicellular and have different types of cells that are suited for a particular function. Bacteria are composed of a single cell but also share the same characteristics just described. There are a few important differences though that will be explained below.
Organelles of the Cell
Eukaryotic cells (all organisms except bacteria and archaea (prokaryotes)) have complex organelles which are surrouned by their own membrane (similar to the cell membrane).
Nucleus – the nucleus is where DNA is stored and where RNA transcription occurs
Mitochondria – often refered to as the “powerhouse” of the cell, this is the organelle that generates ATP (the energy currency of the cell)
Endoplasmic reticulum – the system of membranes used for the folding and transport of proteins. Rough ER (endoplasmic reticulum) is covered by ribosomes while Smooth ER is not. Ribosomes are structures made of protein and rRNA (ribosomal RNA) where proteins are made (translated).
Golgi apparatus – used for modifying and packaging of proteins
Chloroplast – in plants this organelle is responsible for the reactions of photosynthesis
Cell Parts
There are other important components of the cell that are not considered organelles since they are not surrounded by their own lipid bilayer.
Ribosomes – the ribosome is a large complex made of RNA and protein that translates mRNA into protein.
Lysosomes – where the breakdown of nutrients can occur using enzymes
Cell Membrane – this is the structure composed of a lipid bilayer that separates the cell from the outside environment
Cell Wall – found only in plant and bacteria this structure is found outside the cell membrane and serves as a more rigid protective barrier
Differences Between Eukaryotes and Prokaryotes
Bacteria (and archaea which are seldomly mentioned) are prokaryotes. The term prokaryotes is derived from pro (before) and karya (nucleus): before-nucleus = pro-karya = prokaryote. This is because it is thought that bacteria are still very similar to their primitive ancestors which did not have a nucleus. So- bacteria (prokaryotes) do not have a nucleus, while all eukaryotic cells do have a nucleus (this is a popular question for exams- and a common mistake). Bacteria also lack all other membrane bound organelles.
Bacteria do not have:
organelles
nucleus
mitochondria
endoplasmic reticulum
golgi appartus
chloroplast
lysosomes
Bacteria do have:
ribosomes
cell membrane
cell wall (which eukaryotes don’t have)
Its also important to remember that while bacteria don’t have a nucleus they definitely still have DNA organized in a chromosome that is transcribed to mRNA and then translated to protein on a ribosome.
Download the free study guide:
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© 2012 Anthony D'Onofrio
