A tour of a cell. Key Concepts To study cells, biologists use microscopes and the tools of biochemistry Eukaryotic cells have internal membranes that.

A tour of a cell

Key Concepts• To study cells, biologists use microscopes and the

tools of biochemistry• Eukaryotic cells have internal membranes that

compartmentalize their functions• The eukaryotic cell’s genetic instructions are

housed in the nucleus and carried out by the ribosomes

• The endomembrane system regulates protein traffic and performs metabolic functions in the cell

• Mitochondria and chloroplasts change energy from one form to another

• The cytoskeleton is a network of fibers that organizes structures and activities in the cell

Early encounters with cells

Cell theory emerges

• Every organism consists of one or more cells

• The cell is the structural and functional unit of life

• A cell is the smallest unit of life

• Cells contain hereditary information which they pass on to their offspring during division

Our ability to study cells has improved dramatically

Light microscope uses visible light to illuminate a specimen.


Fluorescence microscope allows users to view light emitted from the specimen when it is illuminated with a specific wavelength of light.


Electron microscopes use electrons instead of light.-Transmission electron microscope- electrons form an image after passing through the specimen -Scanning electron microscope- image forms from

electrons that bounce off the surface of the specimen

What have we learned about cells?

There are two main types of cells, prokaryotic and eukaryotic

Prokaryotes Eukaryotes

How are they similar?

Which organisms fall into each category?

How do they differ?

Prokaryotes EukaryotesHow are they similar?


How do they differ?


-All cells have a plasma membrane-All cells contain DNA-All cells contain ribosomes-All cells have cytosol (fluid mixture of water sugar, ions, proteins)-All cells are small (need a large surface are to volume ratio)


How do they differ?




-Bacteria-Archea

-Eukaryotes (plants, animals, protists, fungi)

How do they differ?




-Bacteria-Archea

-Eukaryotes (plants, animals, protists, fungi)

How do they differ?

-Single celled-Not divided into functional compartments

-small in size (1-5µm)-cell wall surrounding the plasma membrane

-single chromosome in a nucleoid region (not membrane-enclosed) also in plasmids (small circular strands of DNA)

-Can be multicellular-Divided into functional compartments (or organelles)-larger in size (10-100µm)-not all eukaryotes have a cell wall surrounding the plasma membrane-many chromosomes in a nucleus (membrane-enclosed)

An overview of the eukaryotic cell

• Watch the animal and plant cell videos

The cell as a city

The eukaryotic cell’s genetic instructions are housed in the nucleus

and carried out by the ribosomes


and carried out by the ribosomesNucleus • Enclosed by the nuclear

envelope• Contains most of the

genes in the eukaryotic cells

• DNA is organized into chromosomes inside the nucleus

• Contains a nucleolus-a place of RNA and ribosome synthesis


and carried out by the ribosomesNucleus • Enclosed by the nuclear

envelope• Contains most of the

genes in the eukaryotic cells

• DNA is organized into chromosomes inside the nucleus

• Contains a nucleolus-a place of RNA and ribosome synthesis

What is a ribosome?



Ribosomes

• Complexes of rRNA and proteins

• They are located on the ER or free in cytoplasm

• Their function is protein synthesis





Are there analogous entities in a city?•DNA•Nucleus•Nuclear envelope•Ribosomes

The endomembrane system regulates protein traffic and performs metabolic

functions in the cell


functions in the cellEndomembrane systemIncludes:•Nuclear envelope•ER•Golgi•Lysosomes•Vacuoles•Plasma membrane


functions in the cellEndoplasmic reticulumSmooth v. Rough

Smooth ER•lacks ribosomes•Involved in synthesis of lipids, metabolism of carbohydrates, and detoxification of poisons

Rough ER•Has attached ribosomes•Makes proteins and phospholipids

Smooth ER

Rough ER

Nuclear envelope

Rough ERSmooth ER

ER lumen

200 nm


functions in the cellEndoplasmic reticulumSmooth v. Rough

Smooth ER•lacks ribosomes•Involved in synthesis of lipids, metabolism of carbohydrates, and detoxification of poisons

Rough ER•Has attached ribosomes•Makes proteins and phospholipids

Smooth ER

Rough ER

Nuclear envelope

Rough ERSmooth ER

ER lumen

200 nm

Transport vesicles-transport materials from the ER to the Golgi


functions in the cellGolgi•Looks like a stack of pancakes


functions in the cellGolgi•Looks like a stack of pancakes•Receives, modifies, manufactures, and stores products of the ER

cis face(“receiving” side of Golgi apparatus)

trans face(“shipping” side of Golgi apparatus)


functions in the cellGolgi•Looks like a stack of pancakes•Receives, modifies, manufactures, and stores products of the ER•Has a cis and trans side

cis face(“receiving” side of Golgi apparatus)

trans face(“shipping” side of Golgi apparatus)


functions in the cellLysosomes (digestive compartments in animal cells)•Sac filled with hydrolytic enzymes (produced by the Golgi)•Its function is to digest macromolecules•Monomers are released to the cytosol for reuse

Nucleus 1 µm

Lysosome

DigestiveenzymesLysosome

Plasmamembrane

Food vacuole

Digestion

Peroxisome

Vesicle

Lysosome

Mitochondrion

Peroxisomefragment

Mitochondrionfragment

Vesicle containingtwo damaged organelles

1 µm

Digestion


functions in the cellVacuolesHave diverse roles•Important in storage•Can conduct hydrolysis

Central vacuole in plants•Hold reserves of organic compounds•Sequester toxins•Helps maintain turgor

Central vacuole

Cytosol

Central vacuole

Nucleus

Cell wall

Chloroplast



Smooth ER

Nucleus

Rough ER

Plasma membrane

cis Golgi

trans Golgi



Are there analogous entities in a city?•Endoplasmic reticulum•Golgi•Lysosomes•Vacuoles•Plasma membrane

Mitochondria and chloroplasts change energy from one form to another


Mitochondria • Found in all eukaryotic cells (about 1-10 µm long)• Contains DNA• Double membrane-bound organelle• Can reproduce on their own• Sites of cellular respiration

Free ribosomesin the mitochondrial matrix

Intermembrane spaceOuter membrane

Inner membrane

CristaeMatrix

0.1 µm


Chloroplasts• Found in plants• Contains DNA• More than one membrane• Can reproduce on their own• Enable plants to convert solar energy to chemical energy (via

photosynthesis)

Ribosomes

Thylakoid

Stroma

Granum

Inner and outer membranes

1 µm


• Specialized metabolic compartments

• Bounded by a single membrane

• Peroxisomes produce hydrogen peroxide and convert it to water

• Oxygen is used to break down different types of molecules (i.e. fatty acids)

Peroxisomes

ChloroplastPeroxisome

Mitochondrion



Are there analogous entities in a city?•Chloroplasts•Mitochondria

The cytoskeleton is a network of fibers that organizes structures and activities in

the cell


the cellThe functions of the cytoskeleton are diverse•Gives mechanical support to maintain cell shape•Providing anchoring for organelles•Can change the shape of a cell•Can move a cell from point A to point B •Can move cell parts


the cellThe components of the cytoskeleton are diverse•Microtubules•Microfilaments•Intermediate filaments


the cellMicrotubulesWhat are they?

•Hollow rods•25 nm in diameter•Made of tubulin•Cable of growing and shrinking by adding or subtracting tubulin

What do they do?•Compression resistant•Shape and support the cell•Tracks along which cellular components move

The cytoskeleton is a network of fibers that organizes structures and activities in the cellMicrotubulesCilia and flagella

•Microtubule-containing extensions of the cell•Locomotion appendages•Both are made of a core of microtubule sheathed in an extension of the plasma membrane

•Cilia and flagella are anchored by a basal body •Eukaryotes have a 9 + 2 arrangement •Each doublet has a dynein (motor protein) associated with it

The cytoskeleton is a network of fibers that organizes structures and activities in the cellMicrofilamentsWhat are they?•Solid rods (7nm in diameter)•Twisted double chain of actin subunits•Can also form branched networksWhat do they do?•Withstand tension (pulling forces)•Network of microfilaments inside the plasma membrane keep cell shape (the cortex)•Important in muscle contraction

Muscle cell

Actin filament

Myosin filamentMyosin arm

(a) Myosin motors in muscle cell contraction

Cortex (outer cytoplasm):gel with actin network

Inner cytoplasm: solwith actin subunits

Extendingpseudopodium

(b) Amoeboid movement

Nonmoving corticalcytoplasm (gel)

Chloroplast

Streamingcytoplasm(sol) Vacuole

Cell wall

Parallel actinfilaments

The cytoskeleton is a network of fibers that organizes structures and activities in the cell

Intermediate filamentsWhat are they?•Fibrous proteins supercoiled into thicker cables•8-12 nm•Formed from diverse proteins including keratinsWhat do they do?•Maintain cell shape (tension-bearing elements)•Anchor the nucleus and other organelles

The cytoskeleton is a network of fibers that organizes structures and activities in the cell

Key Concepts• To study cells, biologists use microscopes and the

tools of biochemistry• Eukaryotic cells have internal membranes that

compartmentalize their functions• The eukaryotic cell’s genetic instructions are housed

in the nucleus and carried out by the ribosomes• The endomembrane system regulates protein traffic

and performs metabolic functions in the cell• Mitochondria and chloroplasts change energy from

one form to another• The cytoskeleton is a network of fibers that

organizes structures and activities in the cell

A tour of a cell. Key Concepts To study cells, biologists use microscopes and the tools of biochemistry Eukaryotic cells have internal membranes that.

Documents

study cells

cell slide

main types of cells

specimen slide

smallest unit of life

division slide

light microscope

cell mitochondria