2-4 Looking 2-4 Looking Inside CellsInside Cells

Parts of the CellParts of the Cell• Cells (which you remember are the Cells (which you remember are the

smallest unit of structure and smallest unit of structure and function in the body) contain function in the body) contain smaller structures called smaller structures called organelles.organelles.

• Organelles carry out specific Organelles carry out specific functions in the cell much as functions in the cell much as organs like the heart and lungs organs like the heart and lungs carry out functions in your body.carry out functions in your body.

From Outside InFrom Outside In

• Plant cellsPlant cells (unlike animal cells) (unlike animal cells) have a rigid layer of non-living have a rigid layer of non-living material surrounding the cell called material surrounding the cell called a a cell wallcell wall. The . The cell wallcell wall acts like the acts like the plants skeleton giving it support.plants skeleton giving it support.

• Inside this plant cells have a Inside this plant cells have a cell cell membranemembrane. Animal cells outermost . Animal cells outermost layer is the cell membrane.layer is the cell membrane.

Cell MembraneCell Membrane

• All cells haveAll cells have cell membranes.cell membranes. It acts It acts like the skin of the cell.like the skin of the cell.

• TheThe main functionmain function of theof the cell membrane cell membrane is to control what substances come into is to control what substances come into and out of a cell.and out of a cell.

• Things cells need like oxygen, water, Things cells need like oxygen, water, and food enter through the cell and food enter through the cell membrane while waste products like membrane while waste products like carbon dioxide leave through it.carbon dioxide leave through it.

NucleusNucleus

• In the center of the cell is a large oval In the center of the cell is a large oval structure called a structure called a nucleusnucleus..

• The The nucleus acts likenucleus acts like the cells “brain”the cells “brain”- it is - it is the control center of the cell the control center of the cell directing all directing all of its activities like growth and of its activities like growth and reproduction.reproduction.

• It is filled with a substance called It is filled with a substance called chromatin.chromatin. Chromatin contains genetic Chromatin contains genetic material, the instructions that direct the material, the instructions that direct the functions of the cellfunctions of the cell. For example, it tells . For example, it tells the cell how to grow.the cell how to grow.

CytoplasmCytoplasmCytoplasmCytoplasm

• The region between the cell membrane The region between the cell membrane and the nucleus is filled with a jelly-like and the nucleus is filled with a jelly-like substance called substance called cytoplasm.cytoplasm.

• Most cell organelles are found floating Most cell organelles are found floating in the cytoplasm.in the cytoplasm.

• These organelles function to produce These organelles function to produce energy, build and transport needed energy, build and transport needed materials, and store and recycle wastes.materials, and store and recycle wastes.

MitochondriaMitochondria

• Mitochondria are bean-shaped organelles in the cell’s cytoplasm that are called the “powerhouse” of the cell because they produce most of the energy the cell needs to carry out its functions.

Endoplasmic ReticulumEndoplasmic Reticulum

• The E.R. is a maze-like collection of passageways surrounding the nucleus.

• They carry proteins and other materials from one part of the cell to another.

RibosomesRibosomes

• RibosomesRibosomes are small, round are small, round structures found throughout the structures found throughout the cytoplasmcytoplasm..

• They function as protein factoriesThey function as protein factories• They pass these proteins on to the They pass these proteins on to the

endoplasmic reticulum. From endoplasmic reticulum. From inside the e.r., they are inside the e.r., they are transported to the golgi bodies.transported to the golgi bodies.

• RibosomesRibosomes are small, round are small, round structures found throughout the structures found throughout the cytoplasmcytoplasm..

• They function as protein factoriesThey function as protein factories• They pass these proteins on to the They pass these proteins on to the

endoplasmic reticulum. From endoplasmic reticulum. From inside the e.r., they are inside the e.r., they are transported to the golgi bodies.transported to the golgi bodies.

Golgi BodiesGolgi Bodies

• Golgi BodiesGolgi Bodies are a flattened bunch are a flattened bunch of sacs and tubes.of sacs and tubes.

• Act like a mailroom. They receive Act like a mailroom. They receive proteins from the e.r. and proteins from the e.r. and distribute them to other parts of distribute them to other parts of the cell and even outside the cell.the cell and even outside the cell.

ChloroplastsChloroplasts

ChloroplastsChloroplasts are found only in are found only in

plantplant cells (and some bacteria).cells (and some bacteria). Their function is to capture the Their function is to capture the

sun’s energy and use it to produce sun’s energy and use it to produce food as energy.food as energy.

Their pigments make the plant Their pigments make the plant green.green.

VacuolesVacuoles

• VacuolesVacuoles are large sacs filled with are large sacs filled with water.water.

• They act as the cell’s water They act as the cell’s water storage tanks.storage tanks.

• Most plants have them, some Most plants have them, some animal cells do, some don’tanimal cells do, some don’t

LysosomesLysosomes

• LysosomesLysosomes are small round are small round structures containing chemicals structures containing chemicals that that break down food and old cell break down food and old cell parts.parts.

• They act like the cell’s cleanup They act like the cell’s cleanup crew.crew.

The other Cell Type:The other Cell Type:

BacteriaBacteria• BacteriaBacteria cells are much smaller than cells are much smaller than

most animal or plant cells.most animal or plant cells.• Bacteria Bacteria like plantslike plants, , do have cell walls do have cell walls

and cell membranes.and cell membranes. • But bacteria But bacteria do not have a nucleusdo not have a nucleus and and

except for ribosomes, none of the other except for ribosomes, none of the other organelles found in animal and plant organelles found in animal and plant cell.cell.

Prokaryotes and Prokaryotes and EukaryotesEukaryotes

• Cells (like bacteria) that have no

nucleus are called Prokaryotes Prokaryotes (which means “before the nucleus” (which means “before the nucleus” because its thought they evolved earlier because its thought they evolved earlier in time before more advanced cells).in time before more advanced cells).

• Cells that Cells that do have a nucleusdo have a nucleus (like plant (like plant and animal cells) are called and animal cells) are called

EukaryotesEukaryotes which means “has a which means “has a nucleus.”nucleus.”