Chapter 6 Cells

6.1 & 6.2Microscopy & Types of Cells

History-Microscopes first used by Renaissance

scientists

-Technology progression developed as cell study developed

-1665: Robert Hooke used a microscope to see dead cells

-1674: Leeuwenhoek created lenses through which he could see living cells

-Light Microscope: Light is passed through the specimen and then through the glass lenses, that refract the light so the image is magnified

-Magnification: The ratio of an object’s image size to its real size

-Resolution: A measure of the clarity of the image

-Contrast: Accentuation of differences in parts of the specimen

-Electron Microscope: Focuses a beam of electrons onto specimen instead of light

-Cell Ultrastructure: Cellular anatomy revealed by EM

-Scanning Electron Microscope(SEM): Used to study the topography of a specimen, creates 3-D images

-Transmission Electron Microscope(TEM): Used to study the internal ultrastructure of cells, uses electromagnets to bend the paths of the electrons

Cell Fractionation-Cell fractionation takes cells apart, separates the major

organelles and other structures from one another-A centrifuge is used to spin the cells in order to

separate their components, applying more than 1 million times the force of gravity

-Cell fractionation allows researchers to prepare certain cell components in bulk

Eukaryotic Cells

Store DNA in nucleus, bound by a double membrane

Internal membranes divide the cell into compartments that

facilitate specific metabolic functions

(organelles)

Larger than prokaryotic cells—can carry out more cellular functions

Surrounded by a phospholipid bilayer

Prokaryotic Cells-Smaller and less complex

than eukaryotic cells

Nucleoid: A dense region of DNA in a prokaryotic cell

DNA is NOT contained in a

nucleus. Instead, it floats in the

cytoplasm

Plant and Animal Cells-Both have most of the same organelles

-Cytoplasm: A semifluid, jellylike substance that contains the organelles and other components of the cell

Plant Cells-Cell Wall-Chloroplasts: Perform photosynthesis-Plasmodesmata: Channels through cell walls that connect the cytoplasms of the adjacent cells-Central Vacuole: Used for storage, breakdown of waste, hydrolysis of macromolecules

Animal Cells-Lysosomes: Digestive organelle where macromolecules are hydrolyzed.-Centrosomes: region where the cell’s microtubules are initiated.-Flagella: locomotion organelle within an extension of the plasma membrane.

-Plasma Membrane: The membrane that encloses the cell, present in both animal and plant cells.

ANIMAL

PLANT

Review 6.1 & 6.2

• Cell Tutorial• Cells

Fig. 6-210 m

1 m

0.1 m

1 cm

1 mm

100 µm

10 µm

1 µm

100 nm

10 nm

1 nm

0.1 nm Atoms

Small molecules

Lipids

Proteins

Ribosomes

Viruses

Smallest bacteria

Mitochondrion

Nucleus

Most bacteria

Most plant and animal cells

Frog egg

Chicken egg

Length of some nerve and muscle cells

Human height

Un

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Fig. 6-5a

Homogenization

Homogenate

Differential centrifugation

Tissuecells

TECHNIQUE

The Nucleus• The nucleus contains most of

the genes in the eukaryotic cell• The nuclear envelope encloses

the nucleus & separates the nucleus from the cytoplasm– The envelope consists of a

double membrane– Pore complexes: each pore

on nuclear envelope is ringed by protein particles

• Nuclear side of envelope lined by nuclear lamina– consists of netlike array of

protein filaments that maintains shape of nucleus

The Nucleus DNA & associated proteins are

organized into cellular structures called chromosomes

Each chromosome made up of chromatinChromatin is the complex of

DNA & proteins that makes up a eukaryotic chromosome

Exists in dispersed form as a mass of long, thin fibers when cell is not dividing (not visible)

Fibers coil up/condense when cell prepares to divide

Each eukaryotic species has a characteristic # of chromosomes

The NucleusA prominent & specialized structure

within the non-dividing nucleus is the nucleolusAppears as mass of densely stained

granules & fibers adjoining part of the chromatin

In the nucleolus: ribosomal RNA (rRNA) is

synthesized from instructions in the DNA

Proteins imported from the cytoplasm are assembled with rRNA into large & small ribosomal subunits

Subunits exit nucleus though nuclear pores where the large & small subunits assemble into a ribosome

RibosomesRibosomes are complexes of

rRNA & protein moleculesfunction as site of protein

synthesis in cytoplasmBuild proteins in 2

cytoplasmic localesFree & bound ribosomes are

identical structurally & can alternate between rolesFree ribosomes are

suspended in the cytosolBound ribosomes are

attached to outside of the endoplasmic reticulum or nuclear envelope

Endomembrane SystemThe endomembrane

system is a collection of membranes inside/around the eukaryotic cellIncludes smooth &

rough endoplasmic reticulum, Golgi apparatus, lysosomes, & vacuoles

The various membranes are not identical in structure

The Endoplasmic ReticulumThe endoplasmic reticulum

consists of membranous tubules & internal, fluid-filled spaces called cisternae

Manufactures membranes & performs many other biosynthetic functions

2 regions that differ in structure & function

Smooth endoplasmic reticulum (sER): so named because it has no ribosomes on the outer surface

Rough endoplasmic reticulum (rER): has ribosomes on the outer surface

Smooth Endoplasmic Reticulum

Rich in enzymes that synthesize lipidsInclude oils, phospholipids, steroids

sER in liver helps detoxify poisons & drugsFrequent use of drugs leads to proliferation

of sER in liver cells increases tolerancesER in muscle cells store calcium ions

sER pumps calcium ions from cytosol & stores them in cisternal space

Rough Endoplasmic ReticulumAbundant in cells that secrete

proteinsAs polypeptides are

synthesized on ribosomes on rER, they are threaded into cisternal space through pores formed by protein complexes in rER membrane

Glycoproteins, proteins to which carbhydratesare attached, are the most secretory polupeptides

rER is also a membrane factoryMembrane-bound proteins

are synthesized directly into membrane

Enzymes in rER also synthesize phospholipids

Golgi ApparatusThe golgi apparatus is the

“shipping & receiving” center of the cellTransport vesicles from the

ER travel to the Golgi for modification of their contents

The Golgi consists of flattened membranous sacs called cisternae2 sides of the Golgi

Cis side: located near ER; receives material by fusing with transport vesicles from ER

Trans side: away from ER; buds of vesicles that travel to other sites

Golgi ApparatusDuring the vesicles’ transit from cis to trans,

the ER products are modifiedThe Golgi also manufactures its own

macromolecules like pectinAlso sorts & packages materials into transport

vesiclesMolecular identification tags are added to

products to help in sortingProducts tagged with identifiers like phosphate

groups identifies the product’s final destination

QuestionsWhat does the nucleolus do?Describe the 2 types of ribosomes. What are

their similarities and their differences?What are the structural and functional

differences between smooth endoplasmic reticulum and rough endoplasmic reticulum?

Describe the roles of transport vesicles.What does the Golgi Apparatus do when the

transport vesicles reach them?

Review Golgi

Organelles

Lysosomes, Vacuoles, Mitochondria, Chloroplasts,

and Peroxisomes

-Sac of hydrolytic enzymes in animal cells used to digest macromolecules-Acids inside membrane neutralize in cytosol

-Large amounts cause autodigestion-Created from Golgi Apparatus-3D molecules prevent dissolving of membrane-Phagocytosis--Food Vacuoles

- Products used as nutrients--Macrophages-Autophagy

-Renew cell-Tay-Sachs Disease

-Lysosome Indigestion

-Food Vacuoles-Contractile Vacuoles

-Filled with water used to balance ion concentration

-Plant Vacuoles-Perform Hydrolysis-Central Vacuole

-Cell Sap-Proteins, ions, pigments,

poisons,-Disposal Site

-Take up large percentage of cell

-Site for Cellular Respiration-Use oxygen to convert sugars and fats to ATP-Nearly all living Protists, Eukaryotes, and Fungi have Mitochondria-Cristae

-Folds used for maximum productivity

-Matrix-Enzymes used to catalyze

Cellular Respiration

-Plastids-Store starches

and Pigments-Photosynthesis

-Produce sugar-Thylakoid-Granum-Stroma

-Contains DNA, enzymes, and ribosomes

MITOCHONDRIA CHLOROPLASTS

Cellular Respiration Cristae Double-layer membrane Matrix Surface Area Plants, Animals, Fungi,

Protists, Eukarya Sugar

Photosynthesis Thylakoids/Grana Double-layer membrane Stroma Ribosomes in

membrane Surface Area Plants Sunlight

-Metabolic, membrane-bound organelle

-Contains enzymes that transfer Hydrogen to produce Hydrogen Peroxide as a by-product (Oxidation)-Break down fatty acids for Mitochondria-Detoxify alcohol-Use enzymes to break down Hydrogen Peroxide

-Sectioned off-Glyoxosomes

-Fat-storing tissues in plants-Enzymes to convert fatty acids to sugar in seeds-Take nutrients from cytosol

6.4 Method lysosomes use to renew the cell Disease associated with defective lysosomes Another thing that uses Phagocytosis 3 of the 5 things offered by cell sap Biggest vacuole and why

6.5 Where ATP synthesis takes place What type of organelle is a Chloroplast? 2 similarities and 2 differences of Mitochondria and

Chloroplasts 2 functions of Peroxisomes Function of Glyoxosomes

Cell Wall (plants only)-Protects Cell Plasma membrane-Controls what enters/leaves Nucleus- Control center Vacuole-Storage Mitochondria- Generates energy Chloroplast (plants only)-Converts into Energy Lysosomes-Digestion/ Sanitation Peroxisomes Ribosomes-Makes proteins Smooth ER-Detoxifies Rough ER-Transports Golgi-Sorts & packages

Cell Wall-plants only

• Protects structure

Plasma membrane

• Controls what enters/leaves

Nucleus

• Control center

Vacuole

• Storage

Mitochondria

• Generates energy

Chloroplast

• Plants only• Converts Sun into Energy

Lysosomes

• Digestion/ Sanitation• Recycle

Peroxisomes

• Break down fatty acids

Ribosomes

• Makes proteins

Smooth ER

• Detoxifies

Rough ER

• Transports

Golgi

• Sorts & packages

Cytoskeleton: a network of fibers extending throughout the cytoplasm.

Organize structures Organize activities Three molecular

structures:◦ Microtubules◦ Microfilaments◦ Intermediate filaments

Mechanical support Maintain shape Certain movements require (Motor

Proteins) Manipulates plasma membrane to make

food vacuoles, and other phagocytic vesicles

Regulates biochemical activities in response to mechanical stimulation

Microtubules: hollow rods measuring 25 nm in diameter and 200 nm in length.

Consists of two subunits:◦ Alpha tubulin◦ Beta tubulin

Shape and support Tracks for organelles equipped with motor

proteins to move

Centrisomes: Microtubules grow out from this, a region that is often located near the nucleus and is considered a “microtubule-organizing center.”

Centrioles: Within the centrosome, a pair of centrioles, each composed of nine sets of triplet microtubules arranged in a ring

Cilia: many microtubule containing extensions that project from some cells

Flagella: a microtubule containing extensions that project from some cells

Movement Also act as signal-receiving antenna for cell Core of microtubules sheathed in extension

of the plasma membrane

Basal Body: structurally very similar to centriole, anchors the flagellum

Dyniens: large motor proteins, each composed of several polypeptides.◦ Responsible for bending movements of organelle

Microfilaments: or (actin filamints) built from molecules of actin, a globular protein.

Twisted double chan of actin subunits Microfilaments can form structural networks Bear tension in the cell Helps support cell shape Cortex: outer cytoplasmic layer of a cell,

semisolid consistency of a gel, in contrast with more fluid state of interior cytoplasm.

◦ Specialized for transporting materials across plasma membrane (intestinal cells, etc.)

◦ Myosin: protein, acts as a microfilament-based motor protein by means of projections that “walk” along the actin filaments.

◦ Pseudopodia: (Greek words pseudes: false, pod: foot) cellular extensions, extend and contract through the reversible assembly of actin subunits

◦ Cytoplasmic streaming: a circular flow of cytoplasm within cells, speeds the distribution of materials within the cell

Intermediate Filaments: specialized for bearing tension, diverse class of cytoskeletal elements. Constructed from different molecular subunits belonging to family of proteins Microtubules and microfilaments are consistent in

diameter and composition, whereas these are not More permanent fixtures of cells Make up nuclear lamina that lines the

interior of nuclear envelope

What is the definition of a cytoskeleton?

What are the three molecular structures of a cytoskeleton?

  What are two functions of the cytoskeleton?  What are required for certain specific kinetic

functions of the membrane?  What are the two subunits of microtubules?

Cytoskeleton

Section 6.6

Structure and Function

• What is it’s Structure?– Fibers Extending in the cytoplasm – Molecular Structures: Microtubules,

Microfilaments, and Intermediate Filaments

• What is it’s Function?– Organizes structures & activities of the Cell– Gives Mechanical Support to the cell

Roles Of CytoSkeleton

Support And Motility

• Important in Animals (Lack Cell Wall!!)

• Motility (Movement) of A Cell– Requires Cytoskeleton +

Motor Proteins– Motor Proteins Bend Cilia

and Flagella by Gripping Microtubules

– Transportation System For Organelles And Vesicles (Monorail)

http://www.traffic.dk/image_uploads/vissues/big_cytoskeletoncover.jpg

Components Of Cytoskeleton

Microtubules• Hollow Rods Constructed From a protein called Tubulin• Thickest Of the Three• Shape and Support the Cell• In Animals, Grows out of Centrosome, function as compression

resisting girders of the cytoskeleton• In Eukaryotes, Beats• Flagella and cilia-propel it through water

•Microtubules •Microfilaments •Intermediate Filaments •http://academic.brooklyn.cuny.edu/biology/bio4fv/page/

cytoseleton1005.JPG

Components of the Cytoskeleton

• Solid rods, built from Acting-Globular Protein (A.K.A: Acting Filaments)

• Structure Role is to bear tension a pulling Force• Gives the Outer Cytoplasmic layer of a cell called

the Cortex, the semisolid consistency of a gel• Arranged Parallel with a thousand others along

the length of a muscle cell with thicker filaments made of Myosin a protein

• Actin and Myosin Contracting is pseudopodia(Amoeba), also cytoplasm streaming ( a circular Flow)

Microfilaments

http://www.cartage.org.lb/en/themes/sciences/Zoology/AnimalPhysiology/Anatomy/AnimalCellStructure/Microfilaments/

microfilament.jpg

Components of the CytoskeletonIntermediate Filaments

• Specialize in bearing tension– Like that of Microfilaments

• Especially important in reinforcing the shape of cells

• After a cell dies they still stand

http://teachernotes.paramus.k12.nj.us/Nolan/2005-2006/index.2.jpg

Questions • Micro Filaments are made of what Globular protein?

• What are Motor Proteins Used For?

• Which is the thickest of the three components?

• What is the Role of a Cytoskeleton?

• Whats the Singular of flagella and Cillia?