Cell OrganellesCell OrganellesChapter 7, page 174Chapter 7, page 174

Modified from an Modified from an original PPT of original PPT of

Beauchemin 2006Beauchemin 2006

Introduction to Cells

Inside a Cell

What is a cell?What is a cell?

A cell is a collection of living matter A cell is a collection of living matter enclosed by a barrier that separates the enclosed by a barrier that separates the cell from its surroundings.cell from its surroundings.

The cell is the basic unit of all forms of life.The cell is the basic unit of all forms of life.

Remember the three parts to cell theory:Remember the three parts to cell theory:

1.1.All living organisms are composed of one All living organisms are composed of one or more cells.or more cells.

2.2.The cell is the basic unit of structure, The cell is the basic unit of structure, function in all organisms.function in all organisms.

3.3.All cells come from preexisting, living cells.All cells come from preexisting, living cells.

(An (An organism is a living thing.)organism is a living thing.)

There are two main categories There are two main categories of cells:of cells:

Prokaryote (prokaryotic cells)Prokaryote (prokaryotic cells) BacteriaBacteria Have no membrane-bound nucleusHave no membrane-bound nucleus Nucleic acid is usually found in “loops” in the Nucleic acid is usually found in “loops” in the

cytoplasmcytoplasm Usually smaller than eukaryotesUsually smaller than eukaryotes Have fewer organelles than eukaryotesHave fewer organelles than eukaryotes

Eukaryotes (eukaryotic cells)Eukaryotes (eukaryotic cells) LargerLarger Have a membrane-bound nucleus where DNA Have a membrane-bound nucleus where DNA

is locatedis located More organellesMore organelles All organisms except bacteria are eukaryotesAll organisms except bacteria are eukaryotes

HomeworkHomework Read pages 174 to 181Read pages 174 to 181 Answer questions 1 to 4 on page 181Answer questions 1 to 4 on page 181 Be able to label both a plant and an animal Be able to label both a plant and an animal

cellcell(use your handouts for practice)(use your handouts for practice)

Cell Organelles in Cell Organelles in EukaryotesEukaryotes

OrganelleOrganelle means means““little organ”little organ”

CytoplasmCytoplasm is is everything inside the everything inside the cell membrane, cell membrane, except the nucleus except the nucleus

Cytosol or the intracellular fluid is the Cytosol or the intracellular fluid is the liquid found inside cells. liquid found inside cells.

Cell MembraneCell MembraneThe boundary of the cellThe boundary of the cell

Cell MembraneCell Membrane

Surrounds the cytoplasm and holds the Surrounds the cytoplasm and holds the shape of the cellshape of the cell

Protects the cellProtects the cell

Allows certain material to pass throughAllows certain material to pass through

((selectively permeable)selectively permeable)

Phospholipid BilayerPhospholipid Bilayer

For more information on the cell membrane, For more information on the cell membrane, please refer to your handout.please refer to your handout.

Cell WallCell Wall

A tough, flexible but A tough, flexible but sometimes fairly sometimes fairly rigid layer that rigid layer that surrounds some surrounds some types of cells. types of cells.

Located outside the Located outside the cell membrane cell membrane

Provides structural support and protection, Provides structural support and protection, sometimes preventing the cell from sometimes preventing the cell from bursting from water entering the cell.bursting from water entering the cell.

Found in plants, some bacteria, fungi, and Found in plants, some bacteria, fungi, and algae.algae.

NucleusNucleusControl center of the Control center of the cellcell

Contains Contains DNA DNA which which contains the coded contains the coded instructions for instructions for making proteins which making proteins which are the molecules that are the molecules that do “everything”.do “everything”.

Nucleus continuedNucleus continuedSurrounded by a Surrounded by a double membrane double membrane called the called the nuclear nuclear membrane membrane or or nuclear envelope.nuclear envelope.

Nuclear envelope has Nuclear envelope has thousands of pores thousands of pores which allow material which allow material to move into and out to move into and out of the nucleus.of the nucleus.

Usually one per cellUsually one per cell

(red blood cells do not have (red blood cells do not have nucleinuclei.).)

Usually the easiest organelle to see under a Usually the easiest organelle to see under a microscopemicroscope

Chromatin in the NucleusChromatin in the Nucleus

The thread-like material in The thread-like material in the nucleus is called the nucleus is called chromatinchromatin which is DNA which is DNA wrapped around protein.wrapped around protein.

Usually looks like this but Usually looks like this but as a cell prepares to as a cell prepares to divide, chromatin divide, chromatin condenses to form condenses to form chromosomeschromosomes..

ChromosomesChromosomes

NucleolusNucleolus

Small dense region Small dense region within the nucleuswithin the nucleus

The assembly of The assembly of ribosomes begins hereribosomes begins here

RibosomeRibosomeProteins are assembled Proteins are assembled by ribosomes, following by ribosomes, following instructions from DNA.instructions from DNA.

Ribosomes are found Ribosomes are found attached to rough attached to rough endoplasmic reticulum endoplasmic reticulum or floating free in or floating free in cytoplasmcytoplasm

Produced in a part of Produced in a part of the nucleus called the the nucleus called the nucleolusnucleolus

Endoplasmic Reticulum (ER)Endoplasmic Reticulum (ER)

The internal membrane The internal membrane system of the cell system of the cell

Connected to the nuclear Connected to the nuclear membranemembrane

Assembles lipid Assembles lipid components of the cell components of the cell membrane, proteins and membrane, proteins and other materials for export other materials for export from the cell.from the cell.

Rough Endoplasmic ReticulumRough Endoplasmic ReticulumStudded with Studded with ribosomesribosomes

Proteins that are Proteins that are being synthesized for being synthesized for export from the cell export from the cell and proteins that are and proteins that are to be used in the cell to be used in the cell membrane are made membrane are made on the these on the these ribosomes. ribosomes.

Proteins synthesized on the ribosomes Proteins synthesized on the ribosomes on the RER enter the RER where they on the RER enter the RER where they may be chemically modified.may be chemically modified.

Smooth Endoplasmic ReticulumSmooth Endoplasmic ReticulumNo ribosomesNo ribosomes

Synthesizes lipidsSynthesizes lipids

Contains many Contains many enzymes which have enzymes which have specialized jobsspecialized jobs

Makes membrane Makes membrane lipids; carries lipids; carries proteins; detoxifies proteins; detoxifies drugsdrugs

Golgi ApparatusGolgi ApparatusLooks like a stack of Looks like a stack of platesplates

Modifies, sorts, and Modifies, sorts, and packages proteins packages proteins and other materials and other materials made in the ER for made in the ER for storage in the cell or storage in the cell or secretion from the secretion from the cell.cell.

Golgi Apparatus (continued)Golgi Apparatus (continued)

Vesicles Vesicles which which contain the contain the materials modified materials modified by the Golgi by the Golgi Apparatus pinch Apparatus pinch off the ends.off the ends.

LysosomesLysosomesClean-up crew Clean-up crew (sometimes called (sometimes called cannibals)cannibals)

Membrane-bound Membrane-bound sacks filled with sacks filled with enzymes that break enzymes that break down lipids, down lipids, carbohydrates and carbohydrates and proteins from food into proteins from food into smaller molecules that smaller molecules that the cell can use.the cell can use.

Which organelles do lysosomes work with?

Lysosomes (continued)Lysosomes (continued)

Also break down Also break down organelles that organelles that have outlived their have outlived their usefulness for usefulness for disposal.disposal.

VacuolesVacuolesStorage container for Storage container for water, food, water, food, enzymesenzymes, , wastes, pigments, etc.wastes, pigments, etc.

Large Large centralcentral vacuole vacuole in in plantplant cells cells

Many small vacuoles Many small vacuoles in in animalanimal cells cells

What type of microscope may have been used to take this picture?

ContractileContractileVacuoleVacuole

Mitochondria Mitochondria (singular = (singular = mitochondrion)mitochondrion)

““Powerhouse of the Powerhouse of the cell”cell”Convert the chemical Convert the chemical energy from food into energy from food into energy that can be energy that can be used by the cell.used by the cell.Enclosed by two Enclosed by two membranes---an outer membranes---an outer one and another that one and another that is folded up inside the is folded up inside the mitochondrionmitochondrion

Mitochondria (continued)Mitochondria (continued)

Cellular respirationCellular respiration occurs here to occurs here to release energy for the cell to userelease energy for the cell to use

Has its own strand of DNAHas its own strand of DNA

Our mitochondria are inherited from our Our mitochondria are inherited from our mothers via the eggs cell. mothers via the eggs cell.

ChloroplastChloroplastFound in plant cellsFound in plant cells

Contains the green Contains the green pigment pigment chlorophyll chlorophyll which captures the which captures the sun’s energy and sun’s energy and converts it into chemical converts it into chemical energy (glucose) in a energy (glucose) in a process called process called photosynthesis.photosynthesis.

CytoskeletonCytoskeletonA network of protein A network of protein filaments/tubes that filaments/tubes that helps the cell maintain helps the cell maintain its shape and which its shape and which helps move materials helps move materials around the cell.around the cell.

Cytoskeleton (cont’d)Cytoskeleton (cont’d)

Acts as Acts as skeletonskeleton and and musclemuscle

Provides shape and structureProvides shape and structure

Microfilaments (1 type of Microfilaments (1 type of cytskeleton)cytskeleton)

Thread-like structuresThread-like structures

Made of a protein called Made of a protein called actinactin

Make a tough, flexible Make a tough, flexible framework that framework that supports the cellsupports the cell

May also help the cell May also help the cell move by assembling move by assembling and disassemblingand disassembling

Microtubules (another type Microtubules (another type ofmicroskeleton)ofmicroskeleton)

Hollow structures Hollow structures made of proteins made of proteins known as tubulinsknown as tubulins

Perform different Perform different functions in different functions in different cells:cells: Critical to maintaining Critical to maintaining

shape of some cellsshape of some cells Form spindles in Form spindles in

mitosis mitosis

Form centrioles (animal cells only)Form centrioles (animal cells only) Build projections from cell’s surface such as Build projections from cell’s surface such as

flagella and cilia that enable some cells to flagella and cilia that enable some cells to “swim” “swim”

Some cells have them arranged so that they Some cells have them arranged so that they can be used to produce controlled movements can be used to produce controlled movements of the cell.of the cell.

CentriolesCentriolesAid in cell divisionAid in cell division

Found in pairs in animal cellsFound in pairs in animal cells

Made of microtubulesMade of microtubules

Cell WallCell WallFound in plant and Found in plant and bacterial cellsbacterial cells

Rigid, protective Rigid, protective barrierbarrier

Located Located outsideoutside of the of the cell membrancell membran

Made of cellulose Made of cellulose (sugar/fiber)(sugar/fiber)

Quick ReviewQuick ReviewWhich organelle is the control center of the cell? Which organelle is the control center of the cell? NucleusNucleus

Which organelle holds the cell together?Which organelle holds the cell together?Cell membraneCell membrane

Which organelles are not found in animal cells?Which organelles are not found in animal cells?Cell wall, central vacuole, chloroplastsCell wall, central vacuole, chloroplasts

Which organelle helps plant cells make food?Which organelle helps plant cells make food?ChloroplastsChloroplasts

What does E.R. stand for?What does E.R. stand for?Endoplasmic reticulumEndoplasmic reticulum