Inside a Cell

Notes Page 16

Very early on, the people studying Very early on, the people studying cellscells knew knew that cells have a great diversity of sizes and that cells have a great diversity of sizes and shapes. As shapes. As microscopesmicroscopes were improved, were improved, scientists could see more and more details of scientists could see more and more details of cells. What they saw was that the inside of cells. What they saw was that the inside of one cell could be very different from the inside one cell could be very different from the inside of another cell. of another cell.

Every cell has a Every cell has a boundaryboundary that separates the that separates the inside of the cell from the outside. That inside of the cell from the outside. That boundary is the cell boundary is the cell membranemembrane, a protective , a protective covering that encloses the entire cell. Any covering that encloses the entire cell. Any material coming material coming intointo or or out out of the cell must of the cell must pass through the cell membrane. Contained pass through the cell membrane. Contained inside the cell membrane is a gelatin-like inside the cell membrane is a gelatin-like material called the material called the cytoplasmcytoplasm. Most of the . Most of the work of the cell is carried out in the work of the cell is carried out in the cytoplasm. cytoplasm.

Scientists separate cells into two broad Scientists separate cells into two broad categories based on one key difference: the categories based on one key difference: the locationlocation of the genetic material cells need to of the genetic material cells need to reproduce and function. In a eukaryotic cell, reproduce and function. In a eukaryotic cell, the genetic material is in a structure called the the genetic material is in a structure called the nucleusnucleus. The nucleus in enclosed by its own . The nucleus in enclosed by its own membrane. Scientists use the word membrane. Scientists use the word organelleorganelle to describe any part of a cell that is to describe any part of a cell that is enclosed by a membrane.enclosed by a membrane.

In a In a prokaryoticprokaryotic cell, there is no separate cell, there is no separate compartment for the genetic material. compartment for the genetic material. Instead, it is in the cytoplasm. Most Instead, it is in the cytoplasm. Most unicellularunicellular organisms are prokaryotic cells. organisms are prokaryotic cells. Almost all multicellular organisms are Almost all multicellular organisms are eukaryoticeukaryotic. .

Check Your Notes

What is the function of a cell membrane?What is the function of a cell membrane?

To protect the cell and control what enters and leaves To protect the cell and control what enters and leaves the cell.the cell.

What is the difference between a prokaryotic cell What is the difference between a prokaryotic cell and an eukaryotic cell?and an eukaryotic cell?

Eukaryotic Cell: NucleusEukaryotic Cell: Nucleus

Prokaryotic Cell: No NucleusProkaryotic Cell: No Nucleus

Plants and animals have eukaryotic cells.

Plant and animal cells, like all eukaryotic cells, Plant and animal cells, like all eukaryotic cells, are divided into are divided into twotwo main compartments. The main compartments. The nucleus, usually the nucleus, usually the largestlargest organelle, is the organelle, is the compartment that stores the instructions the compartment that stores the instructions the cell needs to function. cell needs to function.

Surrounding the nucleus is the Surrounding the nucleus is the cytoplasmcytoplasm. . The cell membrane is the boundary between The cell membrane is the boundary between the cytoplasm and the outside of the cell. the cytoplasm and the outside of the cell. Plant cells also have cell Plant cells also have cell wallswalls. A cell wall is a . A cell wall is a tough outer covering that lies just outside the tough outer covering that lies just outside the cell membrane. The cell wall cell membrane. The cell wall supports and supports and protectsprotects the cell. Having a cell wall is one the cell. Having a cell wall is one important way in which plant cells differ from important way in which plant cells differ from animal cells.animal cells.

Structures That Process Information

The nucleus is often the largest organelle in a The nucleus is often the largest organelle in a cell. It contains information that the cell cell. It contains information that the cell needs to needs to functionfunction. Some of the information is . Some of the information is translated by translated by ribosomesribosomes, tiny structures , tiny structures located in the cytoplasm and endoplasmic located in the cytoplasm and endoplasmic reticulum. Ribosomes use the information to reticulum. Ribosomes use the information to build important molecules called build important molecules called proteinsproteins. .

Organelles that provide energy

No cell can stay alive without No cell can stay alive without energyenergy. Cells . Cells need energy to perform all the activities of need energy to perform all the activities of life. Plants get their energy directly from the life. Plants get their energy directly from the SunSun. Within plant cells are . Within plant cells are chloroplastschloroplasts, , organelles in which the energy from sunlight is organelles in which the energy from sunlight is used to make used to make sugarsugar. Palnts use some of the . Palnts use some of the sugar immediately, to keep their cells sugar immediately, to keep their cells functioning. The rest of the sugar is functioning. The rest of the sugar is stored stored in in their cells.their cells.

Animal cells do not contain chloroplasts. As a Animal cells do not contain chloroplasts. As a result, animals are not able to use the energy result, animals are not able to use the energy of the sun of the sun directlydirectly. Instead, animals get their . Instead, animals get their energy from energy from foodfood. Much of the food an . Much of the food an animal uses for energy comes from the animal uses for energy comes from the sugarsugar that plant cells have stored. Animals get this that plant cells have stored. Animals get this energy by eating energy by eating plantsplants or by eating or by eating animalsanimals that have eaten plants.that have eaten plants.

Check your Notes

How can a chloroplast, a structure found in How can a chloroplast, a structure found in plant cells, but not in animal cells, provide plant cells, but not in animal cells, provide energy for both plants and animals? energy for both plants and animals?

An animal can eat a plant or eat an animal that An animal can eat a plant or eat an animal that has eaten a plant.has eaten a plant.

 Plants use their chloroplasts to create sugars, which animals eat to get energy

Both plant cells and animal cells must be able Both plant cells and animal cells must be able to use energy to do to use energy to do workwork. The energy is . The energy is made available by organelles found in all made available by organelles found in all eukaryotic cells. eukaryotic cells. MitochondriaMitochondria are the are the organelles that use oxygen to get energy from organelles that use oxygen to get energy from processing food. processing food.

Organelles that Process and Transport

You know that plant and animal cells get their You know that plant and animal cells get their energy from the sugars that the organism energy from the sugars that the organism make or consume. Sugars are also an make or consume. Sugars are also an important part of the starting materials that important part of the starting materials that cells use to maintain themselves and cells use to maintain themselves and growgrow. . The job of making cell parts is divided among The job of making cell parts is divided among a number of cell parts in the cytoplasm. a number of cell parts in the cytoplasm.

The endoplasmic reticulum is a system of The endoplasmic reticulum is a system of twisting and winding membranes. Some of twisting and winding membranes. Some of the endoplasmic reticulum contains the endoplasmic reticulum contains ribosomesribosomes, which manufacture proteins. The , which manufacture proteins. The endoplasmic reticulum manufactures parts of endoplasmic reticulum manufactures parts of the the cell membrane.cell membrane.

The endoplasmic reticulum is also part of the The endoplasmic reticulum is also part of the cellular transport system. Portions of the cellular transport system. Portions of the endoplasmic reticulum break off to form small endoplasmic reticulum break off to form small packages called packages called vesiclesvesicles. The vesicles . The vesicles transport processed materials to the Golgi transport processed materials to the Golgi apparatusapparatus (body). The folded membranes of (body). The folded membranes of the Golgi apparatus takes the materials the Golgi apparatus takes the materials manufactured by the endoplasmic reticulum manufactured by the endoplasmic reticulum and finishes processing them.and finishes processing them.

Organelles for Storage, Recycling, and Waste

Cells store water, sugar, and other materials, Cells store water, sugar, and other materials, which they use to which they use to functionfunction. Cells must also store . Cells must also store waste materials until they can be removed. Inside waste materials until they can be removed. Inside plant and fungus cells are sacs called plant and fungus cells are sacs called vacuolesvacuoles. . Vacuoles are enclosed by a membrane and can Vacuoles are enclosed by a membrane and can hold water, waste, and other materials. Vacuoles hold water, waste, and other materials. Vacuoles function with the cell membrane to move materials function with the cell membrane to move materials either into or out of the cell. A plant cell has a either into or out of the cell. A plant cell has a large large central central vacuole in which water and other vacuole in which water and other materials can be stored. materials can be stored. WaterWater in the vacuole in the vacuole provides support for smaller plants. provides support for smaller plants.

Most animal cells do not have central Most animal cells do not have central vacuoles. What animal cells do have are vacuoles. What animal cells do have are similar structures called lysosomes. similar structures called lysosomes. LysosomesLysosomes are vesicles that contain are vesicles that contain chemicals that break down materials taken chemicals that break down materials taken into the cell, as well as old cell parts. into the cell, as well as old cell parts. Remember that animals, unlike plants, take in Remember that animals, unlike plants, take in foodfood. Nutrients brought into the cell need to . Nutrients brought into the cell need to be broken down as well as contained. be broken down as well as contained.

Check your notes

Compare and contrast lysosomes and central Compare and contrast lysosomes and central vacuoles. vacuoles.