2 A&P I The Cell 10

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BIO 110 UNIT II - THE CELLSTRUCTURE & FUNCTION

Chap. 3 pp. 61 - 95

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I. Cell TheoryA. History 1. Robert Hooke - 1668

British scientist - microscope exhibit Thin slice of cork - outer bark of tree Coined the term “cell”

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2. Different scientists examined many different plants and animals for the next 200 years - always found CELLS

B. Cell Theory - 1850s Theory - based upon fact and many observations

1. The cell is the basic unit of structure of all living things

2. The cell is the basic unit of function of all living things

3. All cells come from other pre-existing living cells

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C. Form and Function 1. Something is built in a certain way, for the job it must do

Muscle cells contract - contain contractile proteins Bone cells support and protect - hard calcium

salts 1mm = 1000micrometers(um)

Most cells 40 to 70 um Surface - volume relationship

Surface increases as square of radius Volume increases as cube of radius Volume increases faster than surface area - what do

cells do???

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II. Cell Membrane Structure 1. Physical barrier or boundary around cell 2. Not just a barrier for blockage

Also a gateway for passage through 3a. Permeable membrane = all materials (in

question) can pass through 3b. Semi-permeable or selectively permeable =

some materials can pass through, but others cannot pass through

All biological/cellular membranes are semi permeable

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4. Interested in the chemicals that make up the cell membrane

Fluid Mosaic Model of the Membrane 1972 - Singer and Nicolson

Phospholipids or fats Proteins Carbohydrates Cholesterol

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5. Functions of chemicals

a) phospholipids & cholesterol: Strengthen membrane Increase permeability to other fats/oils Reduce permeability to water and water soluble

chemicals b) proteins: increase solubility to water soluble

chemicals Carriers for transport - aid other chemicals Membrane enzymes - control specific reactions Receptors - on outer surface to allow other

chemicals to react with cell

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5. Functions of chemicals (continued)

c) carbohydrates: Found only on outside surface of membrane Found associated with lipids = glycolipids Found associated with proteins = glycoproteins These chemicals allow the cell to be recognized

as belonging to that individual……and not as a foreign cell

Basis of our immune reactions

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6. Structural arrangement of chemicals

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QuickTime™ and aCinepak decompressorare needed to see this picture.

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20Fig.3.3

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Copyright © 2010 Pearson Education, Inc.

Figure 3.3 Structure of the plasma membrane according to the fluid mosaic model.

Integralproteins

Extracellular fluid(watery environment)

Cytoplasm(watery environment)

Polar head ofphospholipid molecule

Glycolipid

Cholesterol

Peripheralproteins

Bimolecularlipid layercontainingproteins

Inward-facinglayer ofphospholipids

Outward-facinglayer ofphospholipids

Carbohydrate of glycocalyx

Glycoprotein

Filament of cytoskeleton

Nonpolar tail of phospholipid molecule

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23Fig. 3.4

24Copyright © 2010 Pearson Education, Inc.

Figure 3.3 Structure of the plasma membrane according to the fluid mosaic model.

Integralproteins

Extracellular fluid(watery environment)

Cytoplasm(watery environment)

Polar head ofphospholipid molecule

Glycolipid

Cholesterol

Peripheralproteins

Bimolecularlipid layercontainingproteins

Inward-facinglayer ofphospholipids

Outward-facinglayer ofphospholipids

Carbohydrate of glycocalyx

Glycoprotein

Filament of cytoskeleton

Nonpolar tail of phospholipid molecule

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7. Cell membrane has channels or pores (doorway) to let other chemicals pass in

or out of the cell Lipid pore allows fats to easily pass

through Protein pores allows water soluble

materials to pass in or out of the cell Either pores can be open or closed

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8. Membrane is a dynamic structure - both in its chemical make-up and its functions

Constantly capable of change As chemical change, so does the

functions of that membrane/cell Pores opening or closing Solubility changes

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9. Micovilli - folds of the cell membrane to increase surface area

Volume of the cell does not change Surface area increases Pancreas cells during a fast - flat

surface Same cells following eating - look to left Increase transport across membrane


Figure 3.28 Microvilli.

Microvillus

Actinfilaments

Terminalweb

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9. Micovilli - folds of the cell membrane to increase surface area

Volume of the cell does not change

Surface area increases Pancreas cells during a

fast - flat surface Same cells following

eating - look to left Increase transport

across membraneCopyright © 2010 Pearson Education, Inc.


Microvillus

Actinfilaments

Terminalweb

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III. Passive Transport - cell does not expend any energy- is energy expended at all?

A. Diffusion

1. Movement of materials from one area to another

2. Movement - built in to all chemicals - energy of vibration (gases in air: O2 CO2 H2O N2 )

3. Factors influencing vibration Temperature Collisions Charge + or - Gas>liquid>solid

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4. Solute - a chemical (solid) that is mixed or dissolved in a liquid

Solvent - a liquid that a chemical or solute is dissolved in

Concentration - how much solute/solvent ratio 10% salt + 90% water = 100% solution 3% sugar + 97% water = 100% solution

5% sucrose solution in beaker & pool Which is more concentrated?

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5. Equilibrium

A B

10% salt 20% salt

90% H2O 80% H2O

permeable membrane A B

10% salt 20% salt A B

90% H2O 80% H2O A B

15% salt 15% salt

85% H2O 85% H2O EQUILIBRIUM = equal and opposite

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III. B. Facilitative Diffusion 1. no expenditure of cell energy

2. BY ITSELF -a chemical cannot penetrate the cell membrane Amino acids - glucose

3. Chemical plus protein carrier in the cell membrane - together - can move across the membrane

4. Combination of carrier + chemical net diffuses from area of high to area of lower concentration

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Facilitative Diffusion

(a) channel (b) revolving

door channel

See Fig. 3.7b-c in text

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C. Osmosis - passive transport(continued)

1. Osmosis - movement of solvent (water) across a semi-permeable membrane Why is it semi-permeable?

2. Net Osmosis - movement of solvent across a semi-permeable membrane from area of higher solvent concentration to lower solvent concentration

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Fig. 3.8aCopyright © 2010 Pearson Education, Inc.

(a) Membrane permeable to both solutes and water

Solute and water molecules move down their concentration gradientsin opposite directions. Fluid volume remains the same in both compartments.

Leftcompartment:Solution withlower osmolarity

Rightcompartment:Solution with greater osmolarity

Membrane

H2O

Solute

Solutemolecules(sugar)

Both solutions have thesame osmolarity: volumeunchanged

Figure 3.8a Influence of membrane permeability on diffusion and osmosis.

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Fig. 3.8b


(b) Membrane permeable to water, impermeable to solutes

Both solutions have identicalosmolarity, but volume of thesolution on the right is greaterbecause only water is free to move

Solute molecules are prevented from moving but water moves by osmosis.Volume increases in the compartment with the higher osmolarity .

Leftcompartment

Rightcompartment

Membrane

Solutemolecules(sugar)

H2O

Figure 3.8b Influence of membrane permeability on diffusion and osmosis.

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3a. Another example of osmosis

10% sucrose surrounded by 100% H2O

water Will sucrose move through membrane? Will water move through membrane?

Which direction or directions? Net osmosis has water moving into the cell

10% sucrose90% water

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3c. Another example of osmosis


water

after net osmosis into the cell/bag

before water

7+% sucrose93-% water


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3b. Another example of osmosis


waterWater enters due to Water leaves due toCONCENTRATION PRESSURE

INCREASEGRADIENT WITHIN BAG


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4. Osmotic pressure

Measure of the tendency for water to move into a solution due to osmosis

Pressure that develops (or can be calculated) due to net osmosis of water across a semi-permeable membrane

Pressure pushes water one way EQUAL to water moving other way due to concentration gradient = Equilibrium

At equilibrium, pressure does not change

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Figure 3.9 The effect of solutions of varying tonicities on living red blood cells.

Cells retain their normal size andshape in isotonic solutions (same

solute/water concentration as insidecells; water moves in and out).

Cells lose water by osmosis and shrink in a hypertonic solution

(contains a higher concentration of solutes than are present inside

the cells).

(a) Isotonic solutions (b) Hypertonic solutions (c) Hypotonic solutions

Cells take on water by osmosis untilthey become bloated and burst ( lyse )

in a hypotonic solution (contains alower concentration of solutes than

are present in cells).

NOTE - WE NAME THE SOLUTION, BUT IT IS CELL THAT CHANGES SIZE

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D. Passive Transport Summary

1. Diffusion is a slow process Narrow the space or gap for diffusion -

lungs and capillaries Artificially increase concentration gradient

to speed up net diffusion by compartmentalizing a chemical

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B

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•2. Protista - singled celled organism in a hypotonic environment - need a contractile vacuole to remove water that net osmosed into hypertonic cell

3. Plants Young plants hypertonic to environment Water enters Pressure increases inside - turgor pressure Aids in support and growth of young plant

since cell wall not yet rigid Problem with too much fertilizer????

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IV. Active transport

1. Cell expends energy ATP = cellular energy Cell must be alive to produce ATP

2. Carrier protein in membrane requires energy to work (not like facilitative diffusion)

3. Chemical movement from an area of LOW concentration to area of HIGHER concentration (push a rock uphill)

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4. Endocytosis - change in membrane structure to bring a chemical into the cell

a) Phagocytosis - engulfing solid materials

b) Pinocytosis - engulfing fluids / water and solutes dissolved in fluid

5. Exocytosis - release of wastes or secretions from the cell to the outside environment

52Fig. 3.12-13

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V. Internal Area of Cells

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A-B. Nucleus 1. Function - controls metabolism of cell

and its related activities - growth..development..reproduction

2. Nuclear Membrane - semi-permeable (double) membrane that separates nucleus from rest of cell (cytoplasm) Contain pores/breaks in the membrane to

increase permeability

57 Fig. 3.29Copyright © 2010 Pearson Education, Inc.

Figure 3.29 The nucleus.

Chromatin (condensed)

Nuclear envelope Nucleus

Nuclear pores

Fracture line of outermembrane

Nuclear porecomplexes. Each pore is ringed by protein particles.

Surface of nuclear envelope.

Nuclear lamina. The netlike lamina composed of intermediate filaments formed by lamins lines the inner surface of the nuclear envelope.

Nucleolus

Cisternae of rough ER

(a)

(b)

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3. Nuclear Membrane basis of cell classification

Prokaryotic Cell - cells with NO nuclear membrane and no internal membrane structure

Eukaryotic Cell - cells with nuclear membrane plus complex cytoplasmic membranes

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•4. Chromosomes a) consist of DNA (Deoxyribonucleic acid)

& proteins

b) units of genetic information or heredity -”genes”

c) human cell has 46 chromosomes in every cell of the body, except the sex/germ cells

d) all cells have the same 46 chromosomes - how do you “make” a muscle cell vs. bone cell??? Different piano tunes with the same 88 keys Selectively turn genes on and off

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5. Nucleolus

a) 1 or more “balls” of DNA within nucleus

b) function - synthesis of Ribosomes c) ribosomes - make proteins in the

cytoplasm after leaving the nucleus

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Figure 3.2 Structure of the generalized cell.

Secretion beingreleased from cellby exocytosis

Peroxisome

Ribosomes

Roughendoplasmicreticulum

Nucleus

Nuclear envelopeChromatin

Golgi apparatus

NucleolusSmooth endoplasmicreticulum

Cytosol

Lysosome

Mitochondrion

CentriolesCentrosomematrix

Cytoskeletalelements• Microtubule• Intermediate filaments

Plasmamembrane

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C. Cytoplasm and its Organelles

1. Variety of chemicals that all interact, within an area between the cell membrane and the nucleus. Cytoplasm contains membrane bound organelles

2. Solvent water with solutes - Salts Sugars Amino acids Proteins Fats This combination of solutes gives cytoplasm an

interesting property -

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•3. Cytoplasmic Streaming a) sol = liquid/fluid properties

b) gel = semi-solid solute held in 3-D array c) cytoplasmic streaming = cyclosis

Amoeboid movement White blood cell movement

d) factors influencing cyclosis Temperature Pressure Salt concentration

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4. Endoplasmic Reticulum (ER) and Ribosomes

a) network of membranes within the cytoplasm

b) functions of ER: System of channels for transport within the

cell Channels can connect the cell membrane and

the nuclear region Area in cell where steroids (chemicals) are

produced (smooth ER)

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c) Ribosomes

(1) produced in the nucleus by the nucleolus

(2) function in protein synthesis by attaching amino acids together to produce proteins

(3)found in two places Free in cytoplasm = making proteins that stay in

the cell Ribosomes + ER = Rough ER - make proteins that

leave the cell and work extracellularly

67Fig. 3.18Copyright © 2010 Pearson Education, Inc.

Figure 3.18 The endoplasmic reticulum.

Nuclearenvelope

Ribosomes

Rough ER

Smooth ER

(a) Diagrammatic view of smooth and rough ER

(b) Electron micrograph of smooth and rough ER (10,000x)

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5. Golgi Bodies/Apparatus

a) Structure - stack of flatten membranes

b) Function of Golgi - after leaving the ER, many transport vesicles travel to the Golgi and are modified, sorted and shipped

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Figs. 3.20Copyright © 2010 Pearson Education, Inc.

Figure 3.19 Golgi apparatus.

Cis face—“receiving” side of Golgi apparatus

Secretoryvesicle

(a) Many vesicles in the process of pinching off from the membranous Golgi apparatus.

(b) Electron micrograph of the Golgi apparatus (90,000x)

Transport vesiclefrom the Golgi apparatus

Transportvesiclefromtrans face

Trans face—“shipping” side ofGolgi apparatus

New vesiclesforming

New vesicles forming

Cisternae

Transport vesiclefrom rough ER

Golgi apparatus

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Figure 3.22 The endomembrane system.

Golgiapparatus

Transportvesicle

Plasmamembrane

Vesicle

Smooth ER

Rough ER

Nuclear envelope

Lysosome

Nucleus

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b) Function continued

1) store proteins made in the ER 2) Some Golgi synthesize or modify carbohydrates

(previously synthesized) 3) combine carbohydrates to proteins (glycoproteins)

(or glycolipids) 4) package glycoproteins in vesicles 5) vesicle moves towards cell membrane and

releases glycoprotein outside the cell (Secretion) 6) vesicle can become part of the membrane

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Figure 3.20 The sequence of events from protein synthesis on the rough ER to the final distribution of those proteins.

Protein-containing vesicles pinch off rough ERand migrate to fuse with membranes ofGolgi apparatus.

Proteins aremodified withinthe Golgi compartments.

Proteins arethen packagedwithin differentvesicle types, depending ontheir ultimatedestination.

Plasmamem-brane

Secretion byexocytosis

Vesicle becomeslysosome

Golgiapparatus

Rough ER ERmembrane

Phagosome

Proteins incisterna

Pathway B:Vesicle membraneto be incorporatedinto plasmamembrane

Pathway A:Vesicle contentsdestined for exocytosis Extracellular fluid

Secretoryvesicle

Pathway C:Lysosome containing acid hydrolaseenzymes

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3

2

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6. Lysosomes

a) vesicles that are produced by the Golgi, but remain within the cell, and contain strong digestive/hydrolytic enzymes

b) function: Destroy bacteria that enter cell Join with endocytosis vacuole that enters cell with

food source - Protista - and digests food Destroy worn out organelles that do not function

anymore

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6. Lysosome (continued)

c) problem if lysosomes become unstable and its membrane ruptures Digestive enzymes released into cytoplasm Start destroying cell - “suicide bags” Aging has been associated with lysosomal

instability Degenerative diseases of muscles (MD) and

nervous system Attempt to treat with drugs that stabilize lysosomal

membranes

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Fig. 3.21

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7. Vacuole

a) membrane bound storage area of cytoplasm

Store water…food…wastes Animal cells contain numerous, small

vacuoles Plant cells contain one centrally located

vacuole Turgor pressure

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8. Mitochondria

a) “powerhouse” of the cell - production of aerobic cellular energy (ATP)

b) muscle cells need energy - contain many mitochondria

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c) structure - double mosaic membrane with outer and inner membranes Inner contains folds

= Cristae to increase surface area (more chemical reactions = more ATP)

Fig. 3.17Copyright © 2010 Pearson Education, Inc.

Figure 3.17 Mitochondrion.

Enzymes

Matrix

Cristae

Mitochondrial DNA

Ribosome

Outer mitochondrial membrane

Inner mitochondrial membrane

(b)

(a)

(c)

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d) Mitochondria contain DNA

Different from nuclear DNA e) mitochondria from different

organisms contain similar DNA f) billions of years ago - mitochondria

were a free living Prokaryotic bacteria that could use oxygen = Aerobic

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Mitochondria Origin- Hypothesis

Endosymbiosis

Aerobic

Anaerobic

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10. Microtubules and Microfilaments (Fig. 3.24)

a) part of cell / cytoplasm but no membrane surrounding each structure

b) Filaments Protein in nature Thick and thin Function - contractile and/or shape of cell

Muscle protein/contractile protein Movement of Golgi vesicles to outer membrane

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Microvillus

Actinfilaments

Terminalweb

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Figure 3.23 Cytoskeletal elements support the cell and help to generate movement.

Strands made of spherical proteinsubunits called actins

Tough, insoluble protein fibersconstructed like woven ropes

(a) Microfilaments (b) Intermediate filaments (c) Microtubules

Hollow tubes of spherical proteinsubunits called tubulins

Actin subunit

7 nm 10 nm 25 nm

Fibrous subunits

Tubulin subunits

Microfilaments form the blue networksurrounding the pink nucleus in this photo.

Intermediate filaments form the purplebatlike network in this photo.

Microtubules appear as gold networks surrounding the cells’ pink nuclei in this photo.

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c) Microtubules

Arrangement of several microfilaments Transport of materials Maintenance of cell shape Component of cilia and flagella for cell

motility

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Figure 3.24 Microtubules and microfilaments function in cell motility by interacting with motor molecules.

Cytoskeletal elements(microtubules or microfilaments)

Motor molecule (ATP powered)

ATP

(b) In some types of cell motility, motor molecules attached to oneelement of the cytoskeleton can cause it to slide over anotherelement, as in muscle contraction and cilia movement.

ATP

Vesicle

(a) Motor molecules can attach to receptors onvesicles or organelles, and “walk ” the organellesalong the microtubules of the cytoskeleton.

Motor molecule (ATP powered)

Microtubule of cytoskeleton

Receptor for motor molecule

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11. Centrioles

a) animal microtubular arrangement b) pair

c) cell division - organize formation of spindle fibers

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Figure 3.25 Centrioles.

Centrosome matrix

(b)

(a)

Centrioles

Microtubules

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12. Cilia and Flagella

a) microtubular in structure Cilia - numerous, small projections from the

cell surface cell movement or transports materials along the

surface of cell Oar like motion - power stroke plus recovery

Flagellum - 1 or 2 longer microtubular structures for movement of entire cell Sperm or Euglena

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Figure 3.26 Structure of a cilium.

Plasmamembrane

Outer microtubuledoublet

Dynein arms

Centralmicrotubule

Radial spoke

Radial spoke

TEM

TEM

Triplet

Basal body(centriole)

Cilium

Microtubules

Plasmamembrane

Basal body

Cross-linkingproteins insideouter doublets

Cross-linkingproteins insideouter doublets

A longitudinal section of acilium shows microtubules running the length of thestructure.

The doubletsalso have attached motor proteins, the dynein arms.

The outermicrotubule doublets and the two central microtubules are held together by cross-linking proteins and radial spokes.

A cross section through thebasal body. The nine outer doublets of a cilium extend into a basal body where each doublet joins another microtubule to form a ring of nine triplets.

A cross section through thecilium shows the “9 + 2”arrangement of microtubules.

TEM

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Figure 3.27 Ciliary function.

(a) Phases of ciliary motion.

(b) Traveling wave created by the activity ofmany cilia acting together propels mucusacross cell surfaces.

Power, orpropulsive,stroke

Layer of mucus

Cell surface

Recovery stroke, whencilium is returning to itsinitial position

1 2 3 4 5 6 7

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Cells

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13. Summary: Form and Functionsomething is built in a certain way, for the job it will do

Function Cell Structure Stores fats adipose/fat

large vacuole Contracts muscle cell

contractile filaments and mitochondia / energy

Phagocytosis Bacteria white blood cell lysosomes

Release Digestive enzymes - Pancreas Golgi Rough ER Microvilli

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THE END