7.3 Eukaryotic Cell Structures

p. 179 - 187

The Cell TheoryThe Cell Theory

•Cell is the smallest / basic unit of living organisms

•Unicellular organisms are made of one cell only

•The cells of multicellular organisms are specialized to perform different functions

Eukaryotic cell

Prokaryotic cell

Notice the structures in the eukaryote

Two Main Types of Two Main Types of Eukaryotic CellsEukaryotic Cells

Plant Cell

Animal Cell

OrganelleOrganelless

• Very small size

• Can only be observed under a microscope

• Have specific functions

• Found throughout cytoplasm

Plasma membrane = maintains homeostasis

Golgi apparatus = sorts & transports

Nucleus = control center

Mitochondrion = transforms energy

Endoplasmic reticulum = responsible for chemical reactions

vacuole

Free ribosomes

cytoplasm

lysosomecytoskeleton

centriole

nucleolus

ribosomes

A Typical Animal Cell

Cell MembraneCell Membrane

• Gate keeper or a skinny bouncer

• Controls what comes in and out of the cell.

Plasma membranePlasma membrane

• Boundary between the cell and its external environment

• Helps maintain homeostasis

• Allows cell to vary shape as needed

• Controls movement of materials that enter and exit cell

• A continuous double layer of phospholipid molecules

•Lies immediately against the cell wall

•Made of protein and phospholipids

•Selectively permeable

Cell membrane

Cell MembraneCell Membrane

•Living layer

•Controls the movement of materials into and out of the cell

Cell membrane

Cell MembraneCell Membrane

•The protector•Dead layer•Large empty spaces present between cellulose fibers

•Freely permeable

Cell wall

Plant Cell ~ Cell WallPlant Cell ~ Cell Wall

Plant Cell ~ Cell WallPlant Cell ~ Cell Wall

•Made of cellulose which forms very thin fibers

•Strong and rigid•Only found in plant cells

Cell wall

• Protect and support the enclosed substances (protoplasm)

• Resist entry of excess water into the cell

• Give shape to the cell

Cell wall

Plant Cell ~ Cell WallPlant Cell ~ Cell Wall

Controls the normal activities of the cell

•Bounded by a nuclear membrane

•Contains chromosomes - blueprints

NucleusNucleus

•Each cell has fixed number of chromosomes that carry genes.

•Humans have 23 pairs of chromosomes.

•Genes control cell characteristics

Nucleus

NucleusNucleus

nucleusnucleus

• Manages cell functions

• Stores hereditary material

• Includes chromatin and the nucleolus, which produces ribosomes

• Involved in protein synthesis

NucleolusNucleolus

• Cell may have Cell may have 1 to 31 to 3 nucleoli nucleoli• Inside nucleusInside nucleus• DisappearsDisappears when cell divides when cell divides• Makes ribosomesMakes ribosomes that make that make

proteinsproteins

RibosomesRibosomes

•Ribosomes are protein makers

•Jelly-like substance enclosed by cell membrane that contains organelles

•Provides a medium for chemical reactions to take place

Cytoplasm

Cytoplasm / Cytoplasm / cytosolcytosol

•Contains organelles to carry out specific jobs

•Examples: chloroplast & mitochondrion

Cytoplasm

CytoplasmCytoplasm

Cytosol

• The cytosol is the "soup" within which all the other cell organelles reside and where most of the cellular metabolism occurs.

• Though mostly water, the cytosol is full of proteins that control cell metabolism including signal transduction pathways, glycolysis, intracellular receptors, and transcription factors.

Cytoplasm

• This is a collective term for the cytosol plus the organelles suspended within the cytosol.

Smooth & Rough Smooth & Rough Endoplasmic Endoplasmic

ReticulumReticulumSmooth ER lacks ribosomes & makes proteins USED In the cell

Rough ER has ribosomes on its surface & makes proteins to EXPORT

Endoplasmic reticulumEndoplasmic reticulum• Provides a large surface

area on which chemical reactions can take place

• Site for lipid synthesize• Is cell’s delivery system,

providing materials for ribosomes as they synthesize proteins

• Is connected to the nuclear envelope providing a pipeline between the nucleus and the cytoplasm.

Smooth Endoplasmic Smooth Endoplasmic ReticulumReticulum

•Smooth tubes

•no ribosomes

•Makes lipids

•Metabolizes carbohydrates & calcium

•Works in some poison & drug detoxification

•It is important in the creation and storage of steroids.

Rough Endoplasmic Rough Endoplasmic ReticulumReticulum

•bumpy tube or channels

•has ribosomes on its surface

•Attached to the nuclear membrane

•Works with the golgi bodies to export protein to outside cell

Golgi apparatus / golgi Golgi apparatus / golgi bodiesbodies

•Like UPS•Packaging and shipping•Wrap & export proteins

Golgi apparatusGolgi apparatus

• Receives newly synthesized proteins and lipids from the ER and distributes them to the plasma membrane and other cell organelles

• Chemically modifies proteins & lipids (fats), then repackages them for distribution to final destination outside the cell.

Golgi BodiesGolgi Bodies

• Stacks of Stacks of flattened sacsflattened sacs• Have a shipping side & a Have a shipping side & a

receiving sidereceiving side• Receive & Receive & modify modify

proteinsproteins made by ER made by ER• Transport vesiclesTransport vesicles with with

modified proteins pinch modified proteins pinch off the endsoff the ends

Transport

vesicle

• Huge space

• Plants have a large central vacuole

• Contains cell sap… sugars, proteins, minerals, wastes, & pigments

VacuoleVacuole

Vacuole

• In animal cells, the vacuoles are much smaller if there at all.

• There may be more than one in an animal cell.

• The vacuoles are also not found in the center but near the edges.

VacuoleVacuole

Vacuole

LysosomesLysosomes

•Digests & gets rid of wastes•Garbage disposal •Recycling center•They are bacteria killers

LysosomeLysosome

• Contain digestive enzymesContain digestive enzymes• Break down food and worn Break down food and worn

out cell parts for cells out cell parts for cells • Programmed for cell death Programmed for cell death

(lyse & release enzymes to (lyse & release enzymes to break down & recycle cell break down & recycle cell parts)parts)

•Contain the green pigment chlorophyll

•Traps sunlight to make to make sugars (food)

•Process called photosynthesis

Plant Cell ~ Plant Cell ~ ChloroplastChloroplast

Chloropla

st

PlastidsPlastids

• Plant organelles that store starches or lipids or that contains pigments

• Chloroplasts contain pigment so they are plastids

MitochondriaMitochondria

• The “powerhouse” of the cell

• Breaks down food molecules to release energy, which is then stored in other molecules that can power cell reactions easily

•Power plant•Rod shape•Site of Cellular respiration

MitochondriaMitochondria

Mitochondrion( mitochondria )

•Active cells like muscles have more mitochondria•Burn sugars to produce energy ATP

MitochondriaMitochondria

Mitochondria

Different kinds of plant Different kinds of plant cellscells

Onion Epidermal Cells

Root Hair Cell

root hair

Guard Cells

mitochondrion

nucleus

glycogen granule

cell membrane

cytoplasm

Animal cellAnimal cell

•No cell wall or chloroplast

•Stores glycogen in the cytoplasm for food energy

vacuole

Animal Cell ~ CentrioleAnimal Cell ~ Centriole

• Microtubule organizer• Near the nucleus• Paired structures• Help cell divide

Different kinds of animal Different kinds of animal cellscells

white blood cell

red blood cell

cheek cells

sperm

nerve cell

muscle cell

Amoeba

Paramecium

CytoskeletonCytoskeleton

• Provides support for organelles

• Also helps maintain cell shape

• Includes microtubules and microfilaments

Microtubules & Microtubules & Intermediate filamentsIntermediate filaments

* Centrosomes* Centrosomes

• The centrosome, or MICROTUBULE ORGANIZING CENTER (MTOC), is an area in the cell where microtubles are produced.

• Plant and animal cell centrosomes play similar roles in cell division, and both include collections of microtubules, but the plant cell centrosome is simpler and does not have centrioles.

* Peroxisome* Peroxisome • Peroxisomes are membrane-bound packets of

oxidative enzymes.

• In plant cells, peroxisomes play a variety of roles including converting fatty acids to sugar and assisting chloroplasts in photorespiration.

• In animal cells, peroxisomes protect the cell from

its own production of toxic hydrogen peroxide.

• As an example, white blood cells produce hydrogen peroxide to kill bacteria.

• The oxidative enzymes in peroxisomes break down the hydrogen peroxide into water and oxygen.

* Secretory vesicles* Secretory vesicles

• Cell secretions - e.g. hormones, neurotransmitters - are packaged in secretory vesicles at the Golgi apparatus.

• The secretory vesicles are then transported to the cell surface for release.

Similarities between Similarities between plant cells and animal plant cells and animal

cellscellsBoth have a cell membrane surrounding the cytoplasm

Both have a nucleus

Both contain mitochondria

Differences between Differences between plant cells and animal plant cells and animal

cellscells

Animal cells Plant cells

Relatively smaller in

sizeIrregular shape

No cell wall

Relatively larger in size

Regular shapeCell wall present

Animal cells Plant cells

Vacuole small or absent

Glycogen as food storage

Nucleus at the center

Large central vacuole

Starch as food storage

Nucleus near cell wall

Differences between Plant Differences between Plant Cells and Animal CellsCells and Animal Cells