Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells. Protists, fungi,...

Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells.

Protists, fungi, animals, and plants all consist of eukaryotic cells.

They are all bounded by a membrane, called a plasma membrane.

Within the membrane is a semifluid substance, cytosol, in which organelles are found.

All cells contain chromosomes, carrying genes in the form of DNA.

And all cells have ribosomes, tiny organelles that make proteins according to instructions from the genes

Bacterial cell

Animal cell

A major difference between prokaryotic and eukaryotic cells, indicated by their names, is that the chromosomes of a eukaryotic cell are located in a membrane–enclosed organelle called the _______________

. In a prokaryotic cell , the DNA is concentrated in a region called the nucleoid, but no membrane separates this region from the rest of the cell.

In contrast, the eukaryotic cell has a true nucleus, bounded by a membranous nuclear envelope

Within the cytoplasm of a eukaryotic cell, suspended in cytosol, are a variety of membrane–bounded organelles of specialized form and function. These are absent in prokaryotic cells.

The entire region between the nucleus and the plasma membrane is called _____________, a term also used for the interior of a prokaryotic cell.

Within the cytoplasm of a eukaryotic cell, is ________________, which has a variety of membrane–bounded organelles of specialized form and function, suspended in it.

Size is a general aspect of cell structure that relates to function.

The logistics of carrying out cellular metabolism sets limits on cell size.

At the lower limit, the smallest cells known are bacteria called mycoplasmas, which have diameters between 0.1 and 1.0 μm.

Most bacteria are 1–10 μm in diameter, a dimension about ten times greater than that of mycoplasmas.

Eukaryotic cells are typically 10–100 μm in diameter.

Metabolic requirements impose theoretical upper limits on the size that is practical for a single cell.

As an object of a particular shape increases in size, its volume grows proportionately more than its surface area.

(Area is proportional to a linear dimension squared, whereas volume is proportional to the linear dimension cubed.) Book

Thus, the smaller the object, the greater its ratio of surface area to volume

A high surface–to–volume ratio facilitates the exchange of materials between a cell and its environment

At the boundary of every cell, the ______________________functions as a selective barrier that allows sufficient passage of oxygen, nutrients, and wastes to service the entire volume of the cell .

For each square micrometer of membrane, only so much of a particular substance can cross per second.

Rates of chemical exchange with the extracellular environment might be inadequate to maintain a cell with a very large cytoplasm. The need for a surface area sufficiently large to accommodate the volume helps explain the microscopic size of most cells.

A sufficiently high ratio of surface area to volume is especially important in cells that exchange a lot of material with their surroundings, such as ___________cells.

Such cells may have many long, thin projections from their surface called _________________, which ______________________without an appreciable increase in __________________

The plasma membrane.  The plasma membrane and the membranes of organelles consist of a double layer (bilayer) of phospholipids with various proteins attached to or embedded in it.

The phospholipid tails in the interior of a membrane are _____________; the interior portions of membrane proteins are also hydrophobic.

The phospholipid heads, exterior proteins, exterior parts of proteins, and carbohydrate side chains are _____________ and in contact with the aqueous solution on either side of the membrane.

Carbohydrate side chains are found only on the ____________ surface of the plasma membrane.

PIC

glucose + oxygen carbon + water + energydioxide

C6H12O6 6O2 6CO2 6H2O ATP+ + +

In addition to the plasma membrane at its outer surface, a eukaryotic cell has extensive and elaborately arranged internal membranes, which partition the cell into compartments—______________ ______________.

These membranes also participate directly in the cell′s metabolism, because many enzymes are built right into the membranes. Furthermore, the cell′s compartments provide different local environments that facilitate specific metabolic functions, so incompatible processes can go on simultaneously inside the same cell

A little more on eukaryotic cells

…….

The nucleus contains most of the genes in the eukaryotic cell (some genes are located in mitochondria and chloroplasts).

It is generally the most _____________ organelle in a eukaryotic cell, averaging about 5 μm in diameter.

The nuclear envelope encloses the nucleus, separating its contents from the cytoplasm

Functioncontrol center of cellprotects DNA

instructions for building proteins Structure

nuclear membranenucleolus

ribosome factorychromosomes

DNA

.  Within the nucleus are the chromosomes, which appear as a mass of chromatin (DNA and associated proteins), and one or more nucleoli (singular, nucleolus), which function in ________________ synthesis.

The nuclear envelope, which consists of ______ membranes separated by a narrow space, is perforated with pores and lined by the nuclear lamina

nuclearpores

nuclearpore

nuclear envelopenucleolus

histone protein

chromosome

DNA

FunctionControls passage of material

Structurenuclear envelope

double membrane membrane fused in spots to create pores

allows large macromolecules to pass through

What kind of molecules need to pass through?

The nuclear envelope, which consists of two

membranes separated by a narrow space, is perforated with pores and lined by the nuclear lamina.

The two membranes, are separated by a space of 20–40 nm. The envelope is perforated by pores that are about 100 nm in diameter.

At the lip of each pore, the inner and outer membranes of the nuclear envelope are continuous. An intricate protein structure called a pore complex lines each pore and regulates the entry and exit of certain large macromolecules and particles.

Except at the pores, the nuclear side of the envelope is lined by the nuclear lamina, a netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope.

There is also much evidence for a nuclear matrix, a framework of fibers extending throughout the nuclear interior.

Within the nucleus are the chromosomes, which appear as a mass of chromatin (DNA and associated proteins),

and one or more nucleoli (singular, nucleolus), which function in ________________ _________________

Each chromosome is made up of a material called chromatin, a complex of proteins and DNA. Stained chromatin usually appears through both light microscopes and electron microscopes as a diffuse mass.

As a cell prepares to divide, however, the thin chromatin fibers coil up (condense), becoming thick enough to be distinguished as the familiar separate structures we know as chromosomes.

Each eukaryotic species has a characteristic number of chromosomes.

A prominent structure within the nondividing nucleus is the nucleolus (plural, nucleoli ), which appears through the electron microscope as a mass of densely stained granules and fibers adjoining part of the chromatin.

Here a special type of RNA called ribosomal RNA (rRNA) is synthesized from instructions in the DNA.

Also, proteins imported from the cytoplasm are assembled with rRNA into large and small ribosomal subunits in the nucleolus.

These subunits then exit the nucleus through the nuclear pores to the cytoplasm, where a large and a small subunit can assemble into a ribosome..

2007-2008

cellscells

DNADNA

proteinsproteins

organismorganismRepeat after me…Proteins do all the work!

Building proteins read DNA instructionsbuild proteinsprocess proteins

folding modifying

removing amino acidsadding other molecules

e.g, making glycoproteinsfor cell membrane

address & transport proteins

The nucleus directs protein synthesis by synthesizing messenger RNA (mRNA) according to instructions provided by the DNA. ___________________________

The mRNA is then transported to the cytoplasm via the nuclear pores. Once an mRNA molecule reaches the cytoplasm, ribosomes translate the mRNA′s genetic message into the primary structure of a specific polypeptide. _____________________

Organelles involvednucleus ribosomesendoplasmic reticulum

(ER)Golgi apparatusvesicles

nucleus ribosome ERGolgiapparatus

vesicles

The Protein Assembly Line

Organelles involvednucleus ribosomesendoplasmic reticulum

(ER)Golgi apparatusvesicles

nucleus ribosome ERGolgiapparatus

vesicles

The Protein Assembly Line

Making proteins to run daily life & growth, the cell must…

read genes (DNA) build proteins

structural proteins (muscle fibers, hair, skin, claws)enzymes (speed up chemical reactions)signals (hormones) & receptors

organelles that do this work… nucleus ribosomes endoplasmic reticulum (ER) Golgi apparatus

cellsDNA proteins

one of the major job of cells is to make proteins,because…

one of the major job of cells is to make proteins,because… proteins do all the

work!proteins do all the work!

signals

structural

enzymes

receptors

DNA

NucleusmRNA

nuclearmembrane

smallribosomalsubunit

largeribosomalsubunit

cytoplasm

mRNA

nuclear pore

production of mRNA from DNA in nucleus

production of mRNA from DNA in nucleus

mRNA travels from nucleus to ribosome in cytoplasm through nuclear pore

mRNA travels from nucleus to ribosome in cytoplasm through nuclear pore

1

2

Ribosomes, particles made of ribosomal RNA and protein, are the organelles that carry out protein synthesis. Cells that have high rates of protein synthesis have a particularly large number of ribosomes. For example, a human pancreas cell has a few million ribosomes. Not surprisingly, cells active in protein synthesis also have prominent __________________.

Function ribosome production

build ribosome subunits from rRNA & proteins exit through nuclear pores to cytoplasm &

combine to form functional ribosomes

smallsubunit

large subunit

ribosome

rRNA &proteins

nucleolus

smallsubunit

largesubunit

Functionprotein production

StructurerRNA & protein2 subunits combine 0.08m

RibosomesRoughER

SmoothER

membrane proteins

Free ribosomessuspended in cytosolsynthesize proteins that

function in cytosol Bound ribosomes

attached to endoplasmic reticulum

synthesize proteins for export or for membranes

Ribosomes build proteins in two cytoplasmic locales Free ribosomes are suspended in the cytosol, while bound

ribosomes are attached to the outside of the endoplasmic reticulum or nuclear envelope.

Most of the proteins made on free ribosomes function within the cytosol; examples are enzymes that catalyze the first steps of sugar breakdown.

Bound ribosomes generally make proteins that are destined either for

insertion into membranes, for packaging within certain organelles such as lysosomes or for export from the cell (secretion). Cells that specialize in protein secretion—for instance, the

cells of the pancreas that secrete digestive enzymes—frequently have a high proportion of ________ ribosomes.

0.08m

RibosomesRoughER

SmoothER

regulates protein traffic and performs metabolic functions in the cell

Many of the different membranes of the eukaryotic cell are part of an endomembrane system, which carries out a variety of tasks in the cell. These tasks include

synthesis of proteins and their transport into membranes and organelles or out of the cell,

metabolism and movement of lipids, and detoxification of poisons

includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, various kinds of vacuoles, and the plasma membrane (not actually an

endomembrane in physical location, but nevertheless related to the endoplasmic reticulum and other internal membranes). We have already discussed the nuclear envelope and will now focus on the endoplasmic reticulum and the other endomembranes to which the endoplasmic reticulum gives rise

Functionworks on proteins

helps complete the proteins after ribosome builds them

makes membranes Structure

rough ER ribosomes attached works on proteins

smooth ER makes membranes

Function processes proteinsmanufactures membranessynthesis & hydrolysis of many compounds

Structuremembrane connected to nuclear envelope &

extends throughout cell

smooth

Membrane production Many metabolic processes

synthesis synthesize lipids

oils, phospholipids, steroids & sex hormoneshydrolysis

hydrolyze glycogen into glucose in liver

detoxify drugs & poisons in liverex. alcohol & barbiturates

The cells that actually synthesize and secrete SEX hormones—in the testes and ovaries, for example—are rich in ______________, a structural feature that fits the function of these cells

Membrane production Many metabolic processes

synthesis synthesize lipids

oils, phospholipids, steroids & sex hormoneshydrolysis

hydrolyze glycogen into glucose in liver

detoxify drugs & poisons in liverex. alcohol & barbiturates

Detoxification usually involves adding hydroxyl groups to drugs, making them more soluble and easier to flush from the body.

The sedative phenobarbital and other barbiturates are examples of drugs metabolized in this manner by smooth ER in liver cells. In fact, barbiturates, alcohol, and many other drugs induce the proliferation of smooth ER and its associated detoxification enzymes, thus increasing the rate of detoxification

also stores calcium ions. In muscle cells, for example, a specialized smooth ER membrane pumps calcium ions from the cytosol into the ER lumen. When a muscle cell is stimulated by a nerve impulse, calcium ions rush back across the ER membrane into the cytosol and trigger contraction of the muscle cell. In other cell types, calcium ion release from the smooth ER can trigger different responses

Build new membranesynthesize

phospholipids builds membranes

ER membrane expands bud off & transfer to

other parts of cell that need membranes

Produce proteins for export out of cellprotein secreting cellspackaged into transport vesicles for export

Which cellshave lot of rough ER?

DNA

RNA

ribosomes

endoplasmicreticulum

vesicle

Golgi apparatus

vesicle

proteinon its way!

protein finishedprotein

Making Proteins

TO:

TO:

TO:

TO:

cytoplasm

cisternalspace

mRNA

ribosome

membrane ofendoplasmic reticulum

polypeptide

signalsequence

ribosome

transport vesicles

vesiclescarrying proteins

Functionfinishes, sorts, labels & ships proteins

like UPS headquarters shipping & receiving department

ships proteins in vesicles “UPS trucks”

Structuremembrane sacs

vesiclebuddingfrom roughER

fusionof vesiclewith Golgiapparatus

migratingtransportvesicle

protein

ribosome

DNA

RNA

ribosomes

endoplasmicreticulum

vesicle

Golgi apparatus

proteinon its way!

protein finishedprotein

Making Proteins

TO:

TO:

TO:

TO:

nucleus

proteins

transportvesicle

Golgiapparatus

vesicle

smooth ER

rough ER

nuclear porenucleus

ribosome

cellmembrane protein secreted

cytoplasm

2007-2008

Any Questions!!