Cell Structure and FunctionCell Structure and Function(Ch. 7)(Ch. 7)

Movement through the Membrane Overview: http://programs.northlandcollege.edu/biology/biology1111/animations/passive1.swf

Osmosis: http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

Diffusion: http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html

Facilitated Diffusion: http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html

Active Transport: Sodium/ Potassium Pump: http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.htmlCell Signaling: Bacteria Talks TED Talk: http://www.ted.com/talks/bonnie_bassler_on_how_bacteria_communicate

• The invention of the microscope in the The invention of the microscope in the 16001600’’s made possible for cells to be s made possible for cells to be discovered.discovered.– Robert HookeRobert Hooke – examined cork saw many – examined cork saw many

boxes.boxes.– Anton van LeeuwenhoekAnton van Leeuwenhoek - discovered that - discovered that

pond water contained many tiny living pond water contained many tiny living organisms.organisms.

LIFE IS CELLULARLIFE IS CELLULARThe cell – basic unit of life, all living things are made of a The cell – basic unit of life, all living things are made of a cell (cell (unicellularunicellular) or more than one cell () or more than one cell (multicellularmulticellular).).

Cell TheoryCell Theory

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

2.2. In organisms, cells are the basic units of In organisms, cells are the basic units of structure and function.structure and function.

3. New cells are only produced from other 3. New cells are only produced from other existing cells.existing cells.

Cells Are SmallCells Are Small

• A meter is not useful for measuring A meter is not useful for measuring cells.cells.

• Scientists uses a unit called a Scientists uses a unit called a micrometer (micron) to measure cells.micrometer (micron) to measure cells.– 1 micrometer=1/1000 of a millimeter.1 micrometer=1/1000 of a millimeter.

• There are 1000 microns in a mm.There are 1000 microns in a mm.

All cells All cells have a cell membrane, have a cell membrane, genetic material, and cytoplasmgenetic material, and cytoplasm

• The The cell membranecell membrane (aka plasma membrane) (aka plasma membrane) is a flexible, thin barrier that:is a flexible, thin barrier that:– Separates the cell from its surroundings.Separates the cell from its surroundings.– Regulates what moves in and out of the cell.Regulates what moves in and out of the cell.

• Genetic material Genetic material provides instructions that provides instructions that

control the cellcontrol the cell’’s activities.s activities.

• The The cytoplasmcytoplasm is the material inside the cell is the material inside the cell

that supports the organelles.that supports the organelles.

Prokaryotic CellProkaryotic Cell• What is a What is a prokaryoteprokaryote??

– Single celled organisms that lack a nucleus and Single celled organisms that lack a nucleus and

other internal membrane-bound organelles.other internal membrane-bound organelles.

• Genetic material (DNA or RNA) is found free floating in Genetic material (DNA or RNA) is found free floating in

a cell, not in a compartment or nucleus.a cell, not in a compartment or nucleus.

– All bacteria (ex. E. Coli, Streptococcus) are All bacteria (ex. E. Coli, Streptococcus) are

prokaryotic.prokaryotic.

– Prokaryotes are Prokaryotes are unicellularunicellular..

Eukaryotic CellEukaryotic Cell

• What is a What is a eukaryoteeukaryote? (YOU are a eukaryote!)? (YOU are a eukaryote!)

– Have membrane bound organelles (specialized Have membrane bound organelles (specialized

organ-like structures).organ-like structures).

– Genetic material is found in a Genetic material is found in a nucleusnucleus..

– The Kingdoms Animal, Plant, Fungi, and Protista The Kingdoms Animal, Plant, Fungi, and Protista

are Eukaryotes.are Eukaryotes.

– Eukaryotes can be Eukaryotes can be unicellularunicellular or or multicellularmulticellular..

NucleusNucleus• What is the What is the nucleusnucleus??

– Often found in the center of the cell.Often found in the center of the cell.

– Largest and most easily seen organelle.Largest and most easily seen organelle.

– Surface is bound by a double lipid Surface is bound by a double lipid

membrane called the membrane called the nuclear envelopenuclear envelope..• Is a double membrane system.Is a double membrane system.

• Contains Contains nuclear pores nuclear pores - allow for protein and - allow for protein and

other molecules to pass through.other molecules to pass through.

– Genetic materialGenetic material, or , or DNA,DNA, is found here is found here

(in the form of (in the form of chromsomeschromsomes) in eukaryotic ) in eukaryotic

organisms only!organisms only!

NucleolusNucleolus• The The nucleolusnucleolus is… is…

– Structure found inside the Structure found inside the

nucleus.nucleus.

– Responsible for making Responsible for making

ribosomesribosomes which will function which will function

in protein synthesis.in protein synthesis.• Remember that proteins regulate Remember that proteins regulate

cellular processes and make you cellular processes and make you

you!you!

Cellular boundaries

• What is the What is the cell wallcell wall??– Found in many organisms like plants, Found in many organisms like plants,

fungi, algae, and nearly all prokaryotes.fungi, algae, and nearly all prokaryotes.– Not found in animal cells.Not found in animal cells.– Function is to support, provide strength, Function is to support, provide strength,

and protect the cell.and protect the cell.– Composed of the polysaccharide cellulose.Composed of the polysaccharide cellulose.– Are porous and allow water, oxygen, CO2, Are porous and allow water, oxygen, CO2,

and other substances to pass through.and other substances to pass through.

Cellular boundaries• All cells contain a All cells contain a cell membranecell membrane

– Composed of a Composed of a phospholipid bilayerphospholipid bilayer– Regulates what enters and leaves the cellRegulates what enters and leaves the cell– Protects and supports the cellProtects and supports the cell

Organelles that build proteinsOrganelles that build proteins

• What is a What is a ribosomeribosome??

– Protein manufacturer.Protein manufacturer.• Makes proteins to be used within Makes proteins to be used within

the cell or be exported out of the the cell or be exported out of the

cell to be used in other places.cell to be used in other places.

– Are composed of RNA and Are composed of RNA and

protein.protein.

– Produced by the nucleolus Produced by the nucleolus

within the nucleus.within the nucleus.

Organelles that build proteinsOrganelles that build proteins

• The The endoplasmic reticulumendoplasmic reticulum

is…is…

– Found in eukaryotic cells.Found in eukaryotic cells.

– Structure is an extensive system Structure is an extensive system

of internal of internal membranesmembranes..

– Location where lipid Location where lipid

components of the cell components of the cell

membrane are assembled, membrane are assembled,

proteins are exported.proteins are exported.

Organelles that build proteinsOrganelles that build proteins• Rough ERRough ER

– Ribosomes Ribosomes found on the surface.found on the surface.

– Functions to make proteins and transport proteins that will Functions to make proteins and transport proteins that will

be released/secreted from the cell.be released/secreted from the cell.

– Also functions to make proteins destined for lysosomes or Also functions to make proteins destined for lysosomes or

other locations in the cell.other locations in the cell.

• Smooth ERSmooth ER

– Does NOT have ribosomes.Does NOT have ribosomes.

– Contains enzymes for making lipids, detoxification of drugs.Contains enzymes for making lipids, detoxification of drugs.

Organelles that build proteinsOrganelles that build proteins• What is the What is the Gogi apparatusGogi apparatus::

– Receives Receives vesiclesvesicles (transport vacuoles) from (transport vacuoles) from

the RER that contains proteins.the RER that contains proteins.

– Structure in eukaryotic cells that is a stack of Structure in eukaryotic cells that is a stack of

flattened flattened membranesmembranes..

– Modifies molecules that it receives, Modifies molecules that it receives,

packages, and distributes molecules into packages, and distributes molecules into

vesiclesvesicles..• Marks the molecules inside the vesicle to Marks the molecules inside the vesicle to

determine what their final destination will be.determine what their final destination will be.

• Destination is often storage in a vacuole or Destination is often storage in a vacuole or

release to the outside of the cell.release to the outside of the cell.

Organelles that store, clean-Organelles that store, clean-up, and supportup, and support

• What is a What is a lysosomelysosome??

– Organelle filled with digestive Organelle filled with digestive

enzymes.enzymes.

– Digests and recycles the used Digests and recycles the used

components of a cell for reuse.components of a cell for reuse.

– Destroy bacterial cells.Destroy bacterial cells.

– Found in animal cells and Found in animal cells and

specialized plant cells.specialized plant cells.

Organelles that store, clean-up, Organelles that store, clean-up, and supportand support

• What is the role of the What is the role of the vacuolevacuole??

– Store waste products, large amounts of Store waste products, large amounts of

water and nutrients.water and nutrients.

– Help plant cells hold their shape.Help plant cells hold their shape.

– Plant cells have large vacuoles; animal Plant cells have large vacuoles; animal

cells have very small vacuoles.cells have very small vacuoles.

– VesiclesVesicles are transport vacuoles found in are transport vacuoles found in

eukaryotic cells.eukaryotic cells.

• Move materials between organelles Move materials between organelles

and to and from the cell surface.and to and from the cell surface.

Organelles that store, clean-up, Organelles that store, clean-up, and supportand support

• What is the What is the cytoskeletoncytoskeleton??

– Mesh-like network that helps the cell keep its shape.Mesh-like network that helps the cell keep its shape.

– Supports the organelles of the cell.Supports the organelles of the cell.

– MicrotubulesMicrotubules – hollow protein tubes that form the – hollow protein tubes that form the ““trackstracks”” for the for the

organelles to move on.organelles to move on.• CentriolesCentrioles - special microtubules found in animal cells involved in cell - special microtubules found in animal cells involved in cell

division.division.

• CiliaCilia - short thread-like structures important for movement of unicellular - short thread-like structures important for movement of unicellular

organisms.organisms.

• FlagellaFlagella - whip-like microtubules that help unicellular organisms move. - whip-like microtubules that help unicellular organisms move.

– MicrofilamentsMicrofilaments – support the cell and function in helping – support the cell and function in helping

cytoplasm move through the cell.cytoplasm move through the cell.

Organelles that capture & Organelles that capture & release energy (release energy (plastidsplastids))

• What are What are chloroplastschloroplasts??

– Capture sunlight to make sugars – Capture sunlight to make sugars –

photosynthesisphotosynthesis..• Ultimately are the energy source for all Ultimately are the energy source for all

living things.living things.

– Are surrounded by two membranes.Are surrounded by two membranes.

– Contain the green pigment Contain the green pigment

chlorophyllchlorophyll..

– Are not found in animal cells.Are not found in animal cells.

– Contains its own DNA.Contains its own DNA.

Organelles that capture & Organelles that capture & release energy (release energy (plastidsplastids))

• What are What are mitochondriamitochondria??

– Convert the chemical energy stored in Convert the chemical energy stored in

food into useable compounds.food into useable compounds.• ATP is the energy molecule created by the ATP is the energy molecule created by the

cell.cell.

– Made of a double membrane (inner is Made of a double membrane (inner is

folded).folded).

– Also contains its own DNA (from Mom).Also contains its own DNA (from Mom).

– Present in nearly all eukaryotic cells.Present in nearly all eukaryotic cells.

Movement Through the Movement Through the MembraneMembrane

• All cells exist in a liquid environment.All cells exist in a liquid environment.

• The cell membrane functions as a The cell membrane functions as a barrier but must let certain materials in barrier but must let certain materials in and out of the cell.and out of the cell.

Structure of the Plasma/Cell Structure of the Plasma/Cell MembraneMembrane

• Plasma Membranes consist of 2 types of Plasma Membranes consist of 2 types of

molecules – molecules – phospholipidsphospholipids and and proteins.proteins.

• A A phospholipidphospholipid has 2 regions – head and tail. has 2 regions – head and tail.

– Polar head region with a phosphorus group.Polar head region with a phosphorus group.

• Remember, water is polar.Remember, water is polar.

– Non-polar 2 tail region composed of long carbon Non-polar 2 tail region composed of long carbon

chains (fatty acids).chains (fatty acids).

Structure of a phospholipid

Diagram of a PhospholipidDiagram of a Phospholipid

• Polar head Polar head attracts water attracts water molecules molecules ((hydrophilichydrophilic), ), nonpolar tails nonpolar tails repel water repel water molecules molecules ((hyrdrophobichyrdrophobic).).

Phospholipid bilayerPhospholipid bilayer• Due to the hydrophobic Due to the hydrophobic

and hydrophilic nature of and hydrophilic nature of the phospholipid, a double the phospholipid, a double layer is formed where the layer is formed where the heads protect the tails heads protect the tails from the water. from the water. – This is called the This is called the

phospholipid bilayerphospholipid bilayer. . – The bilayer is fluid, not a The bilayer is fluid, not a

hard shell.hard shell.

Structure of phospholipid bilayerStructure of phospholipid bilayer

• The phospholipid bilayer is called The phospholipid bilayer is called semi-semi-

permeable permeable oror selectively permeable selectively permeable – it – it

allows some materials through and blocks allows some materials through and blocks

others.others.

• Polar (head) portion is the true boundary Polar (head) portion is the true boundary

between a cell and its surroundings. between a cell and its surroundings.

Proteins are Embedded Within Proteins are Embedded Within the Bilayer the Bilayer

• ProteinsProteins act as passageways for nonpolar act as passageways for nonpolar

(hydrophobic) molecules to pass through.(hydrophobic) molecules to pass through.

• Without proteins embedded in the bilayer, Without proteins embedded in the bilayer,

essential molecules needed for communication, essential molecules needed for communication,

energy, etc., would not reach the interior of the energy, etc., would not reach the interior of the

cell.cell.

• CarbohydratesCarbohydrates are attached to the proteins. are attached to the proteins.

– Allow for cell recognition and communication.Allow for cell recognition and communication.

Proteins are Embedded Within Proteins are Embedded Within the Bilayer (continued)the Bilayer (continued)

• The model of the lipid bilayer with embedded The model of the lipid bilayer with embedded

proteins is called the proteins is called the Fluid Mosaic Model.Fluid Mosaic Model.

TWO Types of Transport TWO Types of Transport Through a Cell MembraneThrough a Cell Membrane

1.1. Passive TransportPassive Transport – the movement of – the movement of molecules through a cell membrane molecules through a cell membrane withoutwithout the expenditure of energy.the expenditure of energy.

1.1. Active TransportActive Transport – the movement of – the movement of molecules through a cell membrane molecules through a cell membrane usingusing energy.energy.

3 Types of 3 Types of Passive TransportPassive Transport1.1. DiffusionDiffusion - Movement of molecules from - Movement of molecules from

areas of high concentration to low areas of high concentration to low

concentration.concentration.

2.2. OsmosisOsmosis - Diffusion of water molecules - Diffusion of water molecules

from higher concentration of water to lower from higher concentration of water to lower

concentration of water.concentration of water.

3.3. Facilitated DiffusionFacilitated Diffusion - Diffusion through - Diffusion through

pores or channel proteins.pores or channel proteins.

DiffusionDiffusion• Molecules tend to move from areas where there is more of them (Molecules tend to move from areas where there is more of them (high concentrationhigh concentration) )

to where there is less (to where there is less (low concentrationlow concentration).).– This is called moving WITH the concentration gradient.This is called moving WITH the concentration gradient.

• Diffusion continues until Diffusion continues until equilibriumequilibrium is reached, or where molecules are equally is reached, or where molecules are equally distributed. distributed. – Once equilibrium is reached, particles will move at the same rate across the membrane in both Once equilibrium is reached, particles will move at the same rate across the membrane in both

directions.directions.

• If a membrane separates two regions of liquid the solutes within the liquid will move If a membrane separates two regions of liquid the solutes within the liquid will move from high to low. from high to low. – Some solutes will be able to move through when others will not.Some solutes will be able to move through when others will not.

Diffusion (continued)Diffusion (continued)

http://programs.northlandcollege.edu/biology/Biology1111/animations/transport1.html

Facilitated DiffusionFacilitated Diffusion

• Molecules like small lipids and alcohol can Molecules like small lipids and alcohol can diffuse directly through a membrane diffuse directly through a membrane (diffusion). (diffusion).

• Facilitated diffusionFacilitated diffusion occurs because the cell occurs because the cell membrane is semi-permeable and some membrane is semi-permeable and some molecules cannot diffuse through on their molecules cannot diffuse through on their own, they will need assistance (need own, they will need assistance (need facilitated). facilitated).

Facilitated DiffusionFacilitated Diffusion

• Membranes have Membranes have protein channels protein channels that are that are designed to fit specific solutes. When a difference designed to fit specific solutes. When a difference in concentration occurs, solute molecules will in concentration occurs, solute molecules will diffuse through these protein channels.diffuse through these protein channels.– Hundreds of proteins exist to help particles cross Hundreds of proteins exist to help particles cross

membranes.membranes.

• Solute must have a specific size, shape, or polarity Solute must have a specific size, shape, or polarity

in order to fit through the protein channel.in order to fit through the protein channel.

– Is fast and specific!Is fast and specific!

http://programs.northlandcollege.edu/biology/Biology1111/animations/transport1.html

Osmosis: an example of Osmosis: an example of facilitated diffusionfacilitated diffusion

• Water passes through cell membranes Water passes through cell membranes rapidly.rapidly.

• OsmosisOsmosis is a specialized form of facilitated is a specialized form of facilitated diffusion that moves water molecules through diffusion that moves water molecules through membranes via membranes via aquaporinsaquaporins..– AquaporinsAquaporins are special water channel proteins in are special water channel proteins in

membranes.membranes.

OSMOSISOSMOSIS

Types of SolutionsTypes of Solutions– A A hypertonic solution hypertonic solution is one in which the solute is one in which the solute

concentration is HIGHER in the solution than in the cell. concentration is HIGHER in the solution than in the cell. • Water will move out of the cell.Water will move out of the cell.

– A A hypotonic solutionhypotonic solution is one in which the solute is one in which the solute concentration is LOWER in the solution than in the cell.concentration is LOWER in the solution than in the cell.

• Water will move in to the cell.Water will move in to the cell.

– An An isotonic solutionisotonic solution is one in which there are EQUAL is one in which there are EQUAL solute concentrations in the solution and in the cell.solute concentrations in the solution and in the cell.• Water will move in and out of the cell at equal rates.Water will move in and out of the cell at equal rates.

http://programs.northlandcollege.edu/biology/Biology1111/animations/transport1.html

Osmosis: an example of Osmosis: an example of facilitated diffusionfacilitated diffusion

• Osmotic pressureOsmotic pressure –– the pressure that occurs when the pressure that occurs when more water molecules accumulate inside a cell.more water molecules accumulate inside a cell.– Caused by water moving into or out of a cell.Caused by water moving into or out of a cell.

Active processes expend energyActive processes expend energy

• Active transportActive transport is the use of energy to move is the use of energy to move molecules from LOW concentration to HIGH molecules from LOW concentration to HIGH concentration (concentration (against or opposite against or opposite thethe concentration gradient).concentration gradient).

• Some molecules exist in low amounts on one Some molecules exist in low amounts on one side of a membrane and need to be moved to side of a membrane and need to be moved to areas of high amounts.areas of high amounts.

• Cell membranes have mechanisms to move Cell membranes have mechanisms to move these molecules against their concentration these molecules against their concentration gradients.gradients.

http://programs.northlandcollege.edu/biology/Biology1111/animations/transport1.html

Types of Active TransportTypes of Active Transport

• Molecules can be carried through the membrane by Molecules can be carried through the membrane by membrane-associatedmembrane-associated protein pumpsprotein pumps..

– Na, K, Ca ions are transported in this manner.Na, K, Ca ions are transported in this manner.

• Cells have an ability to engulf large particles by Cells have an ability to engulf large particles by forming a vesicle around a particle in a process forming a vesicle around a particle in a process called called endocytosisendocytosis..

– If the particles have been partially broken down into a liquid If the particles have been partially broken down into a liquid of tiny dissolved molecules, it is called of tiny dissolved molecules, it is called pinocytosispinocytosis (cell (cell drinking).drinking).

– If the particles are cell fragments or organic matter, it is If the particles are cell fragments or organic matter, it is called called phagocytosisphagocytosis (cell eating).(cell eating).

Types of Active TransportTypes of Active Transport

• ExocytosisExocytosis is the process by which wastes is the process by which wastes or secretions (hormones) are brought to the or secretions (hormones) are brought to the cell membrane, packaged into vesicles and cell membrane, packaged into vesicles and sent out of the cell.sent out of the cell.

– It is the reverse of endocytosis.It is the reverse of endocytosis.

Unicellular vs. MulticellularUnicellular vs. Multicellular• Unicellular organisms – Unicellular organisms – single celled.single celled.

• Include both prokaryotes and eukaryotes.Include both prokaryotes and eukaryotes.• Maintain homeostasis by growing, responding to Maintain homeostasis by growing, responding to

the environment, transforming energy, and the environment, transforming energy, and reproducing.reproducing.

• Multicellular organisms – Multicellular organisms – many cells many cells working together to create an organism.working together to create an organism.

• Cells are Cells are specializedspecialized – different cell types play – different cell types play different roles.different roles.

• Ex. Move, respond, communicate, substance production.Ex. Move, respond, communicate, substance production.

• Cells communicate with one another to maintain Cells communicate with one another to maintain homeostasis for the organism.homeostasis for the organism.

Levels of organizationLevels of organization• Multicellular organisms have increasing Multicellular organisms have increasing

levels of organization:levels of organization:• OrganellesOrganelles• CellsCells• TissueTissue• OrgansOrgans• Organ systemsOrgan systems• Multi-cellular organismsMulti-cellular organisms

• The organization allows them to divide labor The organization allows them to divide labor in order to maintain homeostasis.in order to maintain homeostasis.

Cellular communicationCellular communication• Cells in large organisms must communicate Cells in large organisms must communicate

with one another in order to work together to with one another in order to work together to maintain homeostasis!maintain homeostasis!

• Occurs via chemical signals that influence the behavior of Occurs via chemical signals that influence the behavior of the cells receiving the signals.the cells receiving the signals.

• ReceptorsReceptors are often found on the outside of cells where are often found on the outside of cells where they bind chemical signaling molecules and influence they bind chemical signaling molecules and influence cellular activity.cellular activity.