CELL ORGANELLESMS. GAYNOR

AP BIOLOGY / CHAPTER 6 (PART 2)

ORGANELLESORGANELLESVery smallPerform various functions for cellFound in the cytoplasmMay or may not be membrane-

bound

BASIC ANIMAL BASIC ANIMAL CELL ORGANELLESCELL ORGANELLES

Nucleolus

Nucleus

Nuclear envelope

Ribosome (attached)Ribosome (free)

Cell Membrane

Rough endoplasmic reticulum

Golgi apparatus

Mitochondrion

Smooth endoplasmicreticulum

Centrioles

BASIC PLANT CELL BASIC PLANT CELL ORGANELLESORGANELLES

CELL OR PLASMA CELL OR PLASMA MEMBRANEMEMBRANE

STRUCTURE Made of double layer (bilayer) of:

phospholipids and proteins Surrounds outside of ALL cellsFUNCTION (JOB) Controls what enters or leaves the cell

Outsideof cell

Insideof cell(cytoplasm)

Cellmembrane

Proteins

Proteinchannel Lipid bilayer

Carbohydratechains

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PHOSPHOLIPIDSPHOSPHOLIPIDSHeads contain glycerol &

phosphate and are hydrophilic (attract water)

Tails are made of fatty acids and are hydrophobic (repel water)

Make up a bilayer where tails point inward toward each other

Can move laterally to allow small molecules (O2, CO2, & H2O to enter)

CELL MEMBRANE IN CELL MEMBRANE IN PLANTSPLANTS

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ADDITIONAL FUNCTION IN PLANTS:

• Pushes out against

the cell wall to maintain cell shape and protect

Cell membrane

CELL WALLCELL WALLSTRUCTURE• Found in:• plants

• Made of cellulose• Fungi

• Made of chitin• Bacteria

• Made of peptidoglycan

FUNCTION (JOB)• Protect• Maintain shape

Cell wall

PLANT CELL WALLPLANT CELL WALL

Two layers of cell wallTwo layers of cell wallPrimary Cell WallPrimary Cell Wall

(Outer )(Outer )CelluloseCellulose onlyonly

Secondary Cell WallSecondary Cell Wall (Inner)(Inner)Cellulose & LigninCellulose & Lignin

Cell membrane is Cell membrane is innermost layerinnermost layer

CYTOPLASM OF A CYTOPLASM OF A CELL CELL

STRUCTURE• Jelly-like substance• Mostly water

• aqueous solutionFUNCTION (JOB)• Provides a solution

for chemical reactions to take place in

• Holds organelles in place

cytoplasm

NUCLEUSNUCLEUSSTRUCTURE• Contains the DNA in

chromosomes• Bounded by a

nuclear envelope (membrane) with pores

• Usually the largest organelle

FUNCTION (JOB)• Controls the normal

activities of the cell

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NUCLEAR ENVELOPENUCLEAR ENVELOPEDouble membrane

surrounding nucleusAlso called nuclear membraneContains nuclear pores for

materials to enter & leave nucleus

Connected to the rough ER

Nuclear pores

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INSIDE THE NUCLEUS The genetic material (DNA) is

found

DNA is spread out And appears as

CHROMATINin non-dividing cells

(NOT TIGHTLY COILED)

DNA is condensed & wrapped around proteins forming

as CHROMOSOMES in dividing cells

(TIGHTLY COILED)

WHAT DOES DNA DO?WHAT DOES DNA DO?DNA is the hereditary

material of the cell

Genes that make up the DNA molecule code for different

proteins

NUCLEOLUSSTRUCTUREInside nucleusInside nucleusCell may have Cell may have 1 to 31 to 3

nucleolinucleoliDisappearsDisappears when cell when cell

dividesdividesFUNCTION (JOB)Makes ribosomes Makes ribosomes

(ribosomal subunits)(ribosomal subunits) 15

CYTOSKELETONCYTOSKELETONSTRUCTURE Made of proteins Microfilaments are

threadlike & made of ACTIN Microtubules are tubelike &

made of TUBULIN

FUNCTION (JOB) Network of fibers that help

cell maintain cell shape Also help move organelles

around

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Table 6.1

STRUCTURE Bean shapeDOUBLE membrane Has its own DNA Folded inner membrane

called CRISTAE (increases surface areafor more chemical reactions)

Interior called MATRIX

MMITOCHONDRIONITOCHONDRION(PLURAL = (PLURAL =

MITOCHONDRIA)MITOCHONDRIA)

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FUNCTION (JOB)“Powerhouse” of cellMakes cellular energy

(ATP)More active cells like

muscle cells have MORE mitochondria

Site of CELLULAR RESPIRATION (burning glucose)

MITOCHONDRION (CON’T)MITOCHONDRION (CON’T)

INTERESTING FACT INTERESTING FACT ------

Mitochondria Come from cytoplasm in the EGG cell during fertilization

Therefore …You inherit your

mitochondria from your mother!

CHLCHLOORROOPLAPLASTSSTS

STRUCTUREBean shapeDOUBLE membraneSacs (“coins”) called

ThylakoidsThylakoids stack called

Granum (pl. =grana)Stroma – gel in middleHas its own DNA

FUNCTION (JOB)Found only in autotrophsCarries out

photosynthesis

RIBRIBOSOMESOSOMESSTRUCTUREMade of PROTEINS and rRNAFUNCTION (JOB)Make proteinsamino acids to make proteinsProcess called TRANSLATION

RIBOSOMES (CON’T)RIBOSOMES (CON’T)

Can be attached to Rough ER (proteins made

exit cell)

OR

Be free (unattached) in the

cytoplasm

(proteins made stay INSIDE cell)

ROUGH ENDOPLASMIC ROUGH ENDOPLASMIC RETICULUM (RER)RETICULUM (RER)

STRUCTUREHas ribosomes on

its surfaceFUNCTION (JOB) Helps to make

proteins for export out of cell

SMOOTH ENDOPLASMIC SMOOTH ENDOPLASMIC RETICULUM (SER)RETICULUM (SER)

STRUCTUREHas NO ribosomes on

its surfaceUsually attached to RERFUNCTION (JOB)Makes lipids

(membranes)Regulates calcium

(muscles)Destroys toxins (Liver) 25

ENDOMEMBRANE SYSTEM

Includes nuclear membrane connected to ER connected to cell membrane

(transport)

GOLGI APPARATUS GOLGI APPARATUS (BODIES)(BODIES)

STRUCTUREStacks of flat sacsLooks like pancakes

with syrup drips“Pankcakes” NOT

connectedFUNCTION (JOB)• Modify• Sort• Package • molecules from ER for

storage OR transport in in transport vesiclestransport vesicles

Transport vesicle

“syrup bubble”

GOLGI BODIESGOLGI BODIESflattened sacsflattened sacsHave a reHave a recceiving eiving

side (side (ccis face) & a is face) & a shipping or shipping or ttransporting side ransporting side ((ttrans face)rans face)Receive proteins Receive proteins

made by ERmade by ERTransport vesicles Transport vesicles

with modified with modified proteins pinch offproteins pinch off

Transport

vesicle

CIS

TRANS

Membrane proteins and lipidsAre synthesized in the ER and Golgi apparatus

ER

Figure 7.10

Transmembraneglycoproteins

Secretoryprotein

Glycolipid

Golgiapparatus

Vesicle

Transmembraneglycoprotein

Membrane glycolipid

Plasma membrane:Cytoplasmic face

Extracellular face

Secretedprotein

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1

2

3

CILIA & FLAGELLACILIA & FLAGELLAFUNCTION (JOB) of FlagellaMoves WHOLE cells

FUNCTION (JOB) of CiliaMoves fluids or small particles across cell surface

CILIA & FLAGELLACILIA & FLAGELLASTRUCTUREMade of protein

tubes called microtubules

Cilia Shorter more numerousFlagella Longer fewer (usually 1-3)

CENTRIOLESCENTRIOLES

STRUCTURE Found only in animal cells

inside CENTROSOMES Paired structures near

nucleus (“t” shape” Made of microtubules

FUNCTION (JOB) Appear during cell division Help to pull chromosome

pairs apart to opposite ends of the cell

CENTRIOLES & THE MITOTIC CENTRIOLES & THE MITOTIC SPINDLESPINDLE

**Made of MICROTUBULES (Tubulin)

LYSOLYSOSOMESSOMESSTRUCTURE They have a low pH Contain Contain hydrolytichydrolytic

digestive enzymesdigestive enzymes

FUNCTION (JOB) Break down Break down food, bacteria &food, bacteria &

old cell partsold cell parts Lyse & Lyse & release enzymesrelease enzymes to to

break down/recycle cell break down/recycle cell partsparts

Programmed forProgrammed for cell death cell death (APOPTOSIS)(APOPTOSIS)

Think= “Think= “LysoLysol” cleanerl” cleaner (a) Phagocytosis: lysosome digesting food

1 µm

Lysosome containsactive hydrolytic

enzymes

Food vacuole fuses with lysosome

Hydrolyticenzymes digestfood particles

Digestion

Food vacuole

Plasma membraneLysosome

Digestiveenzymes

Lysosome

Nucleus

VACUOLESVACUOLESSTRUCTUREFluid filled sacks

for storageSmall or absent

in animal cellsPlant cells have

a large Central Vacuole

Surrounded by a membrane called a TONOPLAST

No vacuoles in bacterial cells

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VACUOLES VACUOLES (CON’T)(CON’T)

FUNCTION (JOB)In plants, vacuoles

store Cell SapIncludes storage of

sugars, proteins, minerals, lipids, wastes, salts, water, and enzymes

CONTRACTILE VACUOLECONTRACTILE VACUOLESTRUCTUREFound in FRESHWATERunicellular protists like

parameciaFUNCTION (JOB)Regulate water intake by

pumping out excess (homeostasis)

Keeps the cell from lysing (bursting)

PEROXISOMESFUNCTION (JOB) Produce hydrogen peroxide (H2O2) and convert it to water H2O2 is also toxic to a cell, and an enzyme made by the

peroxisome can break down H2O2

ChloroplastPeroxisome

Mitochondrion

1 µm

Figure 6.19

INTRACELLULAR JUNCTIONS

ANIMALS: Tight junctions: btw

neighboring cells; prevents leakage between cells

Desmosomes: riveted, anchoring junction; strong sheets of cells

Gap junctions: cytoplasmic channels; allows passage of materials or current between cells

INTRACELLULAR JUNCTIONSPLANTS: Plasmodesmata: cell wall “holes”; water

and solute passage in plants Similar to GAP JUNCTIONS in animals

NOW…LET’S PRACTICE

LIMITS Diffusion limits cell size

Movement from higher [ ] to lower [ ]Larger the distance, slower the diffusion rateA cell 20 cm would require months for

nutrients to get to the centerDNA limits cell size

larger cells need more DNA…Needs more of everything!

Most cells have just one nucleolus

Surface area to volume ratio limits sizeVolume increase

more rapidly than surface area.

Cell size doubles, 8x as much volume, but

only 4x as much surface area