Cell Structure & Cell Structure & Function = Ch 4-5Function = Ch 4-5

Cells= Ch 4Cells= Ch 4• A A cellcell is the smallest unit that can carry is the smallest unit that can carry

on all of the processes of lifeon all of the processes of life• Discovery of CellsDiscovery of Cells

–Hooke Hooke discovered cells in slices of discovered cells in slices of cork.cork.

–Leeuwenhoek Leeuwenhoek first to observe living first to observe living cells in organismscells in organisms

Cell TheoryCell Theory• All living things are composed of 1 All living things are composed of 1

or more cells (uni- vs. multi)or more cells (uni- vs. multi)

• Basic units of structure and Basic units of structure and function in an organismfunction in an organism

• Come only from existing cellsCome only from existing cells

Cell shapeCell shape• Reflects its functionReflects its function

• Cells are DIFFERENTIATED!Cells are DIFFERENTIATED!

Cell SizeCell Size• Although varied, Although varied,

basically all similar in basically all similar in structure & sizestructure & size

• 10 ‑30 micrometers10 ‑30 micrometers• Largest cell = Largest cell = eggseggs

Cells must be small b/c:Cells must be small b/c:• Surface to volume ratio Surface to volume ratio needs to be needs to be highhigh

– LOTS of materialsLOTS of materials need to pass need to pass through cell membrane through cell membrane

• DiffusionDiffusion only works well across very only works well across very short distancesshort distances

• Nucleus Nucleus can only handle so much info at can only handle so much info at once ‑would “short out” if cells were once ‑would “short out” if cells were much largermuch larger

Cellular OrganizationCellular Organization• Multicellular eukaryotes are Multicellular eukaryotes are

organized into:organized into:

• cells→ tissues → organs → cells→ tissues → organs → organ systems → organismsorgan systems → organisms

Two Types of CellsTwo Types of Cells• Prokaryotes Prokaryotes

(only bacteria)(only bacteria)–NO Nucleus NO Nucleus

• Eukaryotes (all Eukaryotes (all other cells)other cells)

–DO Have nucleusDO Have nucleus

• Have cell membrane + cell wallHave cell membrane + cell wall

• NoNo membrane-bound organelles membrane-bound organelles

• NONO NUCLEAR MEMBRANE NUCLEAR MEMBRANE

–DNA in loop in mid-cellDNA in loop in mid-cell

PROKARYOTES (bacteria)PROKARYOTES (bacteria)

EUKARYOTESEUKARYOTES• More More complexcomplex• Contain Contain membrane-bound organellesmembrane-bound organelles

• Includes ALL Includes ALL animals, animals, plants, plants, protists, & protists, & fungifungi

Cell MembraneCell Membrane• Maintain Maintain

homeostasishomeostasis

• Allows interior of Allows interior of cell to differ from cell to differ from its surroundingsits surroundings

• Selectively Selectively Permeable-certain Permeable-certain things allowed things allowed in/outin/out

• Support & protectSupport & protect

Cell MembraneCell Membrane• Phospholipid bi-Phospholipid bi-

layerlayer

“ “Heads” = Heads” = hydrophillic (love water)hydrophillic (love water)

“ “Tails” =Tails” = hydrophobic (fear water)hydrophobic (fear water)

Fluid Mosaic ModelFluid Mosaic Model• Phospholipids Phospholipids

move around - not move around - not staticstatic

Cell MembraneCell Membrane• Embedded with Embedded with proteins, has proteins, has

cholesterol, lipidscholesterol, lipids–Regulate passageRegulate passage of of

materials in & out of cellmaterials in & out of cell

Proteins associated with Proteins associated with the membranethe membrane

• Peripheral: inside or outside Peripheral: inside or outside membranemembrane– Markers that identify cell typeMarkers that identify cell type– Receptors/Carrier Protein that recognize and bind to specific Receptors/Carrier Protein that recognize and bind to specific

BIG substancesBIG substances

• Integral: Extends throughout the Integral: Extends throughout the membranemembrane– Channels/Transport proteins that allow passage of Channels/Transport proteins that allow passage of

materials into/out of cellmaterials into/out of cell

How do the proteins stay in How do the proteins stay in the membrane?the membrane?

• Proteins are made of Proteins are made of different types of amino different types of amino acids (some polar, some not)acids (some polar, some not)

• Non-polar a.a. are in the Non-polar a.a. are in the center part (tail region), and center part (tail region), and the polar a.a. are in the the polar a.a. are in the outside (head region)outside (head region)

NucleusNucleus• Control Control center of the center of the

cellcell

• Contains Contains DNA/genetic DNA/genetic infoinfo

NucleusNucleus• The nucleus is surrounded by a membrane called The nucleus is surrounded by a membrane called

the the nuclear envelope.nuclear envelope.

NucleolusNucleolus• WITHIN the nucleusWITHIN the nucleus• where DNA is concentrated when it is in the where DNA is concentrated when it is in the

process of making ribosomal RNA.process of making ribosomal RNA.

CytoplasmCytoplasm• Space Space between between

cell membrane + cell membrane + nuclear nuclear membranemembrane

• CytosolCytosol is fluid is fluid• Contains Contains

organellesorganelles

CytoskeletonCytoskeleton• Made of protein Made of protein

fibersfibers• Helps cell move & Helps cell move &

maintain shape.maintain shape.• Includes Includes

microtubulesmicrotubules, , microfilamentsmicrofilaments, , intermediate intermediate filamentsfilaments..

CentriolesCentrioles• Two short cylinders of Two short cylinders of

microtubules microtubules

• Involved in animal cell division. Involved in animal cell division.

MitochondriaMitochondria• PowerhousePowerhouse of the of the

cellcell– Converts sugar to Converts sugar to

ATPATP–# varies depending # varies depending

on cell type on cell type

MitochondriaMitochondria• Double membraneDouble membrane• Own DNAOwn DNA

• Previously a prokaryote?Previously a prokaryote?

RibosomesRibosomes• Assembly siteAssembly site for proteins; made for proteins; made

of of rRNArRNA and and proteinsproteins• Free= protein used in cellFree= protein used in cell

• Attached= proteins for exportAttached= proteins for export

Endoplasmic ReticulumEndoplasmic Reticulum

• Transport systemTransport system of the cell of the cell• Amount of E.R. varies with cell activityAmount of E.R. varies with cell activity

• ROUGH E.R.ROUGH E.R. - -

ribosomes ribosomes assemble/produce assemble/produce proteins prepares for export or proteins prepares for export or insertion into the cell membrane.insertion into the cell membrane.

• SMOOTH E.R.SMOOTH E.R. – –

– Builds lipids and participates Builds lipids and participates in detoxification of toxins.in detoxification of toxins.

Golgi ApparatusGolgi Apparatus• Packaging & SecretingPackaging & Secreting• Membrane-bound Membrane-bound storage sacsstorage sacs that pinch off that pinch off

vesiclesvesicles to send products to the cell's to send products to the cell's membrane/surfacemembrane/surface

VesiclesVesicles• Include: Include: lysosomeslysosomes (digestive enzymes) (digestive enzymes)

and and peroxisomesperoxisomes (detoxification (detoxification enzymes)enzymes)

• Classified by their contents.Classified by their contents.• Protein SynthesisProtein Synthesis

– Rough ER, Golgi apparatus, and vesicles work Rough ER, Golgi apparatus, and vesicles work together to transport proteins to their together to transport proteins to their destinations in/out of cell.destinations in/out of cell.

Flagella (few) & Cilia (many)Flagella (few) & Cilia (many)• Hair-like, extend from cellHair-like, extend from cell

• Used for movement, prey captureUsed for movement, prey capture

Cell ComponentsCell ComponentsAnimal CellAnimal Cell

Plant CellPlant Cell

•Cell WallCell Wall•Central Central VacuoleVacuole•PlastidsPlastids

Cell WallCell Wall• RigidRigid

• Provides support and Provides support and protectionprotection

• Outside the Plasma membrane

VacuolesVacuoles• Membrane‑bound space filled Membrane‑bound space filled

with water + with water + dissolved dissolved solutes; solutes; provides provides support in support in plant cells plant cells

• Store enzymes & metabolic wasteStore enzymes & metabolic waste

PlastidPlastid• Store starch and pigments. Store starch and pigments.

ChloroplastChloroplast• Double-membranedDouble-membraned

• For photosynthesis & storageFor photosynthesis & storage

Comparing CellsComparing Cells

Homeostasis & TransportHomeostasis & TransportChapter 5Chapter 5

Cellular TransportCellular Transport• Cells transport substances into Cells transport substances into

and out of the cell to maintain and out of the cell to maintain homeostasishomeostasis

• Two categories of transportTwo categories of transport–Passive (no energy required)Passive (no energy required)–Active (energy required)Active (energy required)

Diffusion (passive Diffusion (passive transport)transport)

• Mixing of two substances by random Mixing of two substances by random movement of molecules (kinetic movement of molecules (kinetic energy) from an area of HIGH energy) from an area of HIGH concentration to a LOW concentration concentration to a LOW concentration

• ““DownDown” a ” a concentration gradientconcentration gradient

• DiffusionDiffusion

–Eventually reaches Eventually reaches EQUILIBRIUMEQUILIBRIUM

–equilibrium = no concentration equilibrium = no concentration gradientgradient

Diffusion across Diffusion across membranesmembranes

• Ability depends on:Ability depends on:

–size size

–solubility solubility

–nature of membrane nature of membrane

OsmosisOsmosis

OsmosisOsmosis• Diffusion of Diffusion of WATERWATER

through a cell through a cell membrane, from membrane, from areas of areas of highhigh water water concentrationconcentration to to area of area of lowlow water water concentrationconcentration

Water PotentialWater Potential• HypotonicHypotonic = More water, LESS = More water, LESS

SOLUTE – outside cellSOLUTE – outside cell

• HypertonicHypertonic = less water, MORE = less water, MORE SOLUTE – outside cellSOLUTE – outside cell

• IsotonicIsotonic = equal water, EQUAL = equal water, EQUAL SOLUTESOLUTE

Osmosis in Plant CellsOsmosis in Plant Cells• Water constantly flows into plants Water constantly flows into plants

(hypotonic) b/c water is absorbed by roots (hypotonic) b/c water is absorbed by roots and presses against the cell wall…it will not and presses against the cell wall…it will not burst b/c of burst b/c of turgor pressureturgor pressure

• Plants will wilt via Plants will wilt via plasmolysisplasmolysis because there because there is not enough water and water rushes out is not enough water and water rushes out (hypertonic(hypertonic))

Facilitated Diffusion Facilitated Diffusion (passive transport)(passive transport)

• Uses integral (carrier) Uses integral (carrier) proteins move stuff proteins move stuff in/outin/out

• Proteins are specific for Proteins are specific for moleculesmolecules

• Stops when equilibrium Stops when equilibrium is reachedis reached

Ion Channels (passive Ion Channels (passive transport)transport)

• Proteins (carrier) in the membrane that Proteins (carrier) in the membrane that transport ionstransport ions

• Protein is specific for ionProtein is specific for ion

• May be “gated” or always openMay be “gated” or always open

Active TransportActive Transport• Requires energyRequires energy• Protein Protein pumpspumps pass molecules in pass molecules in

only one directiononly one direction• Enables a cell to “stockpile” stuffEnables a cell to “stockpile” stuff• Goes Goes upup concentration gradient concentration gradient

–From LOW to HIGH concentration= From LOW to HIGH concentration= uphilluphill

Important Protein PumpsImportant Protein Pumps• 1. Sodium-Potassium Pump—this allows Na1. Sodium-Potassium Pump—this allows Na+ +

and Kand K++ into and out of cells….important in into and out of cells….important in nerve and muscle cells to keep this “firing” nerve and muscle cells to keep this “firing” and sending messages!and sending messages!

• 2. Proton Pump—in photosynthesis…pumps 2. Proton Pump—in photosynthesis…pumps HH++ (from water splitting) across chloroplast (from water splitting) across chloroplast membrane to make ATP for plant processesmembrane to make ATP for plant processes

Pumps in your bodyPumps in your body

• Sodium - Sodium - potassium: Move potassium: Move sodium out and sodium out and potassium inpotassium in

• 3 Na3 Na+ + out 2 K out 2 K ++ in in• ATP drives pumpATP drives pump

Sodium-potassium pumpSodium-potassium pump• Creates charge gradient to Creates charge gradient to

conduct electrical impulses - conduct electrical impulses - impt. For nervous systemimpt. For nervous system

What about extra large What about extra large particles? How do they get particles? How do they get

into and out of cell?into and out of cell?

Endocytosis - ingestionEndocytosis - ingestion• Uses vesicles to ingest Uses vesicles to ingest

macromolecules, external macromolecules, external fluidfluid

• PinocytosisPinocytosis – – cellular cellular drinkingdrinking

• PhagocytosisPhagocytosis – – cellular eatingcellular eating

Exocytosis - excretionExocytosis - excretionExcrete proteins, waste, toxins