Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells. Protists, fungi, animals, and plants all consist of eukaryotic cells.

All cells have several basic features in common: 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

Basic differences between prokaryotic and eukaryotic cells 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.

Difference between Cytoplasm and Cytosol 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.

Cell size matters! 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.

Why a cell can’t be too large 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

Which part is responsible for exchange of material between cell and its surroundings? 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 __________________

How does plasma membrane look like? 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

Membrane-bound Enzymes glucose + oxygen  carbon + water + energy dioxide C6H12O6 6O2 6CO2 6H2O ATP  +

What are endomembranes? 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: Genetic Library of the Cell 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

Nucleus Function Structure control center of cell protects DNA instructions for building proteins Structure nuclear membrane nucleolus ribosome factory chromosomes DNA Nucleus

The nucleus and its envelope .  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

NUCLEAR ENVELOPE Function Controls passage of material Structure histone protein chromosome DNA Function Controls passage of material Structure nuclear envelope double membrane membrane fused in spots to create pores allows large macromolecules to pass through nuclear pores pore nuclear envelope nucleolus What kind of molecules need to pass through?

The nucleus and its envelope. 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.

What is on the inside of nuclear envelope ? 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 ________________ _________________

chromosome is made up… 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.

Nucleolus 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..

Building Proteins 2007-2008

Proteins do all the work! cells Repeat after me… Proteins do all the work! DNA organism

Cells functions Building proteins read DNA instructions build proteins process proteins folding modifying removing amino acids adding other molecules e.g, making glycoproteins for cell membrane address & transport proteins

Protein Synthesis (an introduction) 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. _____________________

Building Proteins Organelles involved The Protein Assembly Line nucleus ribosomes endoplasmic reticulum (ER) Golgi apparatus vesicles The Protein Assembly Line Golgi apparatus nucleus ribosome ER vesicles

Building Proteins Organelles involved The Protein Assembly Line nucleus ribosomes endoplasmic reticulum (ER) Golgi apparatus vesicles The Protein Assembly Line Golgi apparatus nucleus ribosome ER vesicles

2. Cells need workers = proteins! 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

Proteins do all the work! one of the major job of cells is to make proteins, because… proteins do all the work! structural enzymes signals receptors DNA proteins cells

production of mRNA from DNA in nucleus nuclear membrane 1 production of mRNA from DNA in nucleus small ribosomal subunit large cytoplasm mRNA nuclear pore 2 mRNA travels from nucleus to ribosome in cytoplasm through nuclear pore

Ribosomes: Protein Factories in the Cell 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 __________________.

Nucleolus Function ribosome production build ribosome subunits from rRNA & proteins exit through nuclear pores to cytoplasm & combine to form functional ribosomes small subunit large subunit ribosome rRNA & proteins nucleolus

(Keep in mind that both nucleoli and ribosomes, unlike most other organelles, are not enclosed in membrane.)

Ribosomes Function Structure protein production rRNA & protein small subunit large Ribosomes Function protein production Structure rRNA & protein 2 subunits combine 0.08mm Ribosomes Rough ER Smooth

Types of Ribosomes Free ribosomes Bound ribosomes suspended in cytosol synthesize proteins that function in cytosol Bound ribosomes attached to endoplasmic reticulum synthesize proteins for export or for membranes membrane proteins

Function of ribosomes and their types 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. 0.08mm Ribosomes Rough ER Smooth

The endomembrane system 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

The endomembrane system 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

Endoplasmic Reticulum Function works on proteins helps complete the proteins after ribosome builds them makes membranes Structure rough ER ribosomes attached smooth ER

Endoplasmic Reticulum Function processes proteins manufactures membranes synthesis & hydrolysis of many compounds Structure membrane connected to nuclear envelope & extends throughout cell

Types of ER smooth

Smooth ER function Membrane production Many metabolic processes synthesis synthesize lipids oils, phospholipids, steroids & sex hormones hydrolysis hydrolyze glycogen into glucose in liver detoxify drugs & poisons ex. 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

Smooth ER function Membrane production Many metabolic processes synthesis synthesize lipids oils, phospholipids, steroids & sex hormones hydrolysis hydrolyze glycogen into glucose in liver detoxify drugs & poisons ex. alcohol & barbiturates

How does detoxification happen? 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

The smooth ER 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

Membrane Factory Build new membrane synthesize phospholipids builds membranes ER membrane expands bud off & transfer to other parts of cell that need membranes Membrane Factory

Rough ER function Produce proteins for export out of cell protein secreting cells packaged into transport vesicles for export Which cells have lot of rough ER?

endoplasmic reticulum nucleus endoplasmic reticulum protein on its way! DNA TO: RNA vesicle TO: TO: vesicle ribosomes TO: protein finished protein Golgi apparatus Making Proteins

Synthesizing proteins cytoplasm cisternal space mRNA ribosome membrane of endoplasmic reticulum polypeptide signal sequence Synthesizing proteins ribosome

Golgi Apparatus Function Structure finishes, sorts, labels & ships proteins like UPS headquarters shipping & receiving department ships proteins in vesicles “UPS trucks” Structure membrane sacs vesicles carrying proteins transport vesicles

Golgi Apparatus

Vesicle transport vesicle budding from rough ER fusion of vesicle with Golgi apparatus migrating transport protein ribosome Vesicle transport

endoplasmic reticulum nucleus protein on its way! DNA TO: RNA vesicle TO: TO: ribosomes TO: protein finished protein Golgi apparatus Making Proteins

cytoplasm nucleus cell membrane nuclear pore protein secreted rough ER transport vesicle Golgi apparatus smooth ER rough ER nuclear pore nucleus ribosome cell membrane protein secreted cytoplasm

Any Questions!! 2007-2008