1a Eukaryotic Cells→Membrane Bound Organelle→Cytoskeleton→Tissue

Structure of Simple Epithelial Tissue?

Cells are usually attached to basement membrane that is not made out of cells but rather of different types of fibers (collagen). Basement membrane is semi-permible to some molecules and this is important since epithelial tissue is AVASCULAR. They have no blood vessels. So the only way they can get nutrients is from underlying tissue. Nutrients must move through basement membrane to epithelial tissue.

How do centrioles differ from flagella?

Centriles consist of nine triplets of microtubules around hollow center vs. flagella consist of 9 doublets outside and two inside 9+2

Eukaryotic cells contain: Membrane Bound Organelles. What does that mean?

Each cell has cell membrane that is enclosing cytosol in which organelles are suspended. Membrane bound organelles allow compartmentalization of function. Organelles are well defined large scale structures that have a particular set of functions in the cell. Some organelles such as cilia, centrioles, and ribosomes are not isolated from the cytoplasm of the cell. "Membrane bound" organelles are completely surrounded by a plasma membrane, or even a double membrane. These organelles allow different sets of chemical reactions to be separated from each other so that they do not interfere. This allows the cell to provide radically different environments that allow each reaction to operate most efficiently.

AXONAL TRANSPORT:

Kenisin and dynein are able to transport substances in two directions. From soma to synaptic terminal and back to soma. Movement of the substances is called AXONAL TRANSPORT or AXOPLASMIC TRANSPORT.

Lysosome and Apoptosis:

Lysosome can secrete these enzymes to the cytoplasm of cell and process known as AUTOLYSIS will take place. This will lead to APOPTOSIS.

What is the name of the enzyme that brakes down oxygen peroxide in peroxisome?

Many metabolic pathways produce peroxide as side product H₂O₂. Peroxisome will isolate/pick up peroxide and it contains special enzyme called: CATALASE that can brake down peroxide to water and oxygen.

We say that epithelial cells are polarized:

Meaning that one site faces lumen (the hollow site of the organ) or outside world while the other site of the cell faces blood vessels. For example; in small intestine one site of the cell will be involved in absorption of the nutrients while the other one will be releasing these nutrients into circulation.

Microfilaments and Amoeba cell trying to get food:

Microfilament help to extend the cell and capture food.

Structure of Microfilaments: ACTIN

Microfilaments are made out of ACTIN protein. Many actin proteins will come together to form actin polymer. They are not hollow.

How does that transport happen?

Microtubules form a network inside the neuron that runs from soma to synaptic terminal. It acts as road track and different substances are moved along this track with help of 2 proteins: KENISIN AND DYNEIN. They move: synaptic vesicles, proteins, lipids, organelles such as mitochondria.

Microtubules function in internal transport in neurons:

Most molecules in neuron are made in soma and they must be transported down to axon and synaptic terminal.

Notice that:

Not all the cells have the same amount of organelles. Cells like sperm that needs a lot of energy for locomotion might have many mitochondria. But read blood cells that transport oxygen don't have room for mitochondria. Cells that do a lot of secretion (pancreatic islet cells) might have a lot of Golgi and RER.

Nuclear Pore:

Nuclear pores allow mRNA to exit nucleus, also DNA replication machinery must enter nucleus for DNA replication to happen. But nuclear pore is very selective and it recognize special signals that allow proteins and enzyme to enter nucleus.

MICROTUBULE ORGANIZING CENTER

One end of the microtubule will be attached to a place in cell called MICROTUBULE ORGANIZING CENTER. At the end Microtubules can be extended or shortener by adding to removing tubulin molecules. So microtubules are dynamic.

A child is diagnosed with enzyme deficiency that prevents production of hydrogen peroxide. What would be the outcome of such a deficiency?

Peroxisomes are dependent on peroxide for their function. This would result in inability to brake down fatty acids. These fatty acids would build up in peroxisomes and cell would eventually die.

What are Microtubules, Microfilaments and intermedia filaments are made of?

Protein.

Transport of proteins from ER to Golgi:

Proteins are transported in vesicles that bud off ER and fuse with Golgi.

What is the difference in proteins that are translated in Rough ER vs. the one translated in cytoplasm?

Proteins made in cytoplasm will end up in nucleus, mitochondria, peroxisome or they might stay in cytoplasm. Proteins that are synthesized on Rough ER will be secreted into extracellular environment, they might end up being integral protein in cell membrane or they might remain in: ER, lysosome, Golgi.

Function of Rough ER:

Rough ER has ribosomes on it which permits translation of proteins so this is site of PROTEIN SYNTHESES. Also POST TRANSLATION MODIFICATION: formation of disulfide bridge. Its located closer to Nucleus.

What is the Theory behind Mitochondria?

Serial Endo-symbiosys explains formation of some of the membrane bound organelles such as mitochondria. The Theory says that one prokaryotes swallowed another one. And they are able to establish symbiotic relationship. Chloroplast in plants is believed to evolved in the same way.

Functions of Smooth ER:

Smooth ER lacks ribosomes. Its main function is: 1) lipid synthesis that might be part of cell membrane and these that are secreted from cell like steroid hormones 2) detoxification of toxin and drugs. Smooth ER also transports proteins from Rough ER to Golgi. So smooth ER is closer to Golgi.

Lets Look at the examples of Connective tissue: BONE or OSSEOUS TISSUE

The cells in the osseous tissue are called: OSTEOCYTES. Matrix is known as BONE MINERAL or HYDROXYAPATITE which is collagen fibers with different minerals with magnesium and calcium.

In most organs epithelial cells make up the PARENCHYMA:

The functioning part of the organ. Example: nephrons in kidney, hepatocytes in liver and acid producing cells of stomach are all made out of epithelial cells.

How is nucleus connected to ER?

The other membrane of nucleus is continues and it makes up ER. So the inside environment of ER is the same as environment between the inner and outer nuclear membrane.

ASTERS:

There are also ASTRAL MICROTUBULES. Centrioles and the astral microtubules are called ASTER.

BASAL BODIES:

These are Microtubules organizing centers in cells that have cilia or flagella. Basal Body serves as anchor for flagella or cilia. Cells in respirator system have cilia that help move mucus up. Sperm cell have flagella. Notice that flagella in eukaryotes is different then in prokaryotes.

Structure of microtubules:

They are made out of 2 proteins: α Tubulin β Tubulin α and β Tubulin will join together to form dimer. These dimers will then form microtubules which are hollow.

Structure of Intermedia filaments:

They are not dynamic. They are permanent so they don't change shape or length. They provide structural support for cell and they resist mechanical stress. They are very stable. Proteins that usually make up intermedia filaments are: keratin and desmine.

PEROXISOME:

They have many functions. They bake down long fatty acids by β oxidation, they participate in synthesis of phospholipids and contain some enzymes that are involved in PPP. However there is ONE main and VERY important Function: They pick up oxygen peroxide and isolate it from the cell. This is the Site where reactive oxidative species such as peroxide is reduced to non-toxic forms.

Epithelial Tissue:

Think of it as lining. Both inner and outer lining. Epithelial Tissue makes up out the outher layer of skin, outer layer of organs, it lines organs and cavities. Epithelial tissue also makes out Glands: Exocrine glands and endocrine glands.

Lets Look at the examples of Connective tissue: AREOLAR Tissue

This is very common type of connective tissue and it binds other tissues together providing flexibility and cushioning. In this picture you can see cells (small dots), Fibers running through it and ground substance is liquid background.

Special type of Epithelial Tissue:

Tissue lining blood and lymphatic vessels have special name: ENDOTHELIUM

How Golgi Apparatus knows where to deliver protein?

Usually by adding signal sequences. These signal sequences direct the delivery of the proteins into specific location in cell.

Where can you find simple epithelial tissue?

Usually in places that substances must diffuse in easy way. Aviola in lungs must diffuses oxygen to blood.

Microfilaments are dynamic:

What that means is that they change length frequently. They become longer by actin polymerization and become shorter in process of actin depolarization. Microfilaments are involved in gross movement o the cell. One example is during cell division when cell becomes pinched and then divides to 2 separate cells→CYTOKINESIS.

What is the function of CENTRIOLE?

When cell is replicating and undergoing mitosis centrioles will duplicate and they will end up on either cite of the cell. In metaphase part of mitosis MITOTIC SPINDLE WILL FORM. Microtubules will hold to chromosomes in very specific way. They will become shorter and pull chromosomes apart. SO the main function of Centrioles is to be anchoring microtubules in space while chromosomes are separated.

What is the first distinction that we can make among living organisms?

Whether they are made out of Prokaryotic or Eukaryotic cells.

Endoplasmic Reticulum (ER):

You can have: smooth ER or rough ER. ER is series of membranes that are connected to nucleus. Inside ER is hollow-LUMEN

Structure of GOLGI:

Golgi is organelle made of many tubes. Tube closest to ER is called: Cis Stack. Proteins traveling from ER will first fuse with Cis Stack then they will fuse with Medial Stack and will eventually end up in Trans stack. As protein is moving from stack to stack it is modified in different ways. Protein will bud off from Trans stack and it can: move to lysosome, Plasma membrane, secretory vesicles →these are part of the secretory pathway.

What are the functions of CONNECTIVE TISSUE?

-It supports other tissue -it connects tissues

CENTROSOME:

-Its organelle found near nucleus It's composed of 2 rods. Each of these rods is called: CENTRIOLE. They are made out of triplets of microtubules and are hollow inside. There are 9 triplets that make out one centriole.

Diameters of microtubules,

-Microtubules have diameter of 25nM -Intermedia Filaments have diameter of 10nM -Microfilament have diameter of 7nM

Golgi Apparatus:

-Notice that Golgi is right next to ER -Materials from ER are transferred to Golgi apparatus in vesicles. -Once in Golgi there can be: 1) modification of proteins that are made in Rough ER by addition of carbohydrates, phosphates and sulfate. 2) It sorts and sends proteins to proper destinations 3) Synthesizes molecules that needs to be secreted from cell

Nuclear envelope:

-Nuclear envelope is 2 membranes: Outer and inner membrane -Nuclear envelope allowed for compartmentalization of transcription and translation of DNA into proteins.

Epithelial tissue comes in 2 forms:

-Simple which means its one layer thick -Stratify with has more then one layer

Mitochondria:

-They have 2 membranes and matrix -They have their own small circular DNA so they can make their own proteins. Not all of them but some. They are SEMIAUTONOMUS which means that they contain their own DNA. They replicate independently from nucleus via binary fusion. They are know as "power house of cell" and keep cells alive however they can also kill cell by secreting enzymes from electron transport chain→APOPTOSIS

Lets Look at the examples of Connective tissue: FIBROUS CONNECTIVE TISSUE

-This tissues is very strong. It provides support and shock absorbance for bones and organs. -Its is Found in tendons, dermis-middle of the skin, ligaments.

Lets look at the cross section of the cell. There are 3 components of the cytoskeleton: microfilaments, intermedia filaments and microtubules.

-cell membrane, mitochondria, ER, Ribosomes STRUCTURES OF CYTOSKELETON: 1. MICROTUBULES→they are involved in mitotic spindle, cilia (hair like production outside the cell), flagella (tail like), and they also help transport things within the cell. 2. INERMIDIA FILAMENTS→they provide structural support. They are all over the cell and help resist technical stress. 3. MICROFILAMENTS→involved in movement of the entire cell from within. During the cell division cell will get pinch in the middle and then separate. How does the cell separates apart to divide into 2 cells? Microfilaments.

What makes cell Eukaryotic?

-compartmentalization where organelles are separated by membranes. So they can perform different functions. -nucleus -cells divide through mitosis

The Nucleus:

-contains all genetic material needed for cell replication DNA -nucleus is surrounded by nucleus membrane or nuclear envelope and filled with nucleoplasm -nuclear pores allow for selective two-way exchange of material between cytoplasm and nucleus.

CYTOSKELETON:

-it provides structural support -helps the cell to maintain its shape -helps with movements -helps transport substances whiting cell

What is NUCLEOLUS?

-this is the place in nucleus where ribosomal RNA (rRNA) is synthesized. So this is the placed where ribosomes are put together. -It takes up 25% of nucleus and it can be identify as dark spot. -very densely packed

There are different microtubules organizing centers. We will talk about 2:

1) CENTROSOME 2) BASAL BODY Both of these are similar in structure but microtubules attached to them carry out different functions.

There are 4 different tissues that are made out from Eukaryotic Cells:

1) EPITHELIAL 2) CONNECTIVE 3) MUSSCLE 4) NERVOUS Lets talk more about Epithelial and connective tissue

Microfilaments cen generate force:

Actin filaments can use ATP to generate force for movement by interacting with myosin during muscle contraction.

Examples of Connective Tissue?

Bones, cartilage, blood, lymph, adipose, membrane covering brain and spine and other.

Proteins that are secreted from cell or become part of the cell membrane they follow what is known as "SECRETORY PATHWAY"

But how the proteins know to be part of the secretary pathway? All proteins begin being translated in cytoplasm but the ones that need to follow the secretary pathway contain the signal sequence. That signal is detected early on in translation and the peptide in pushed into Rough ER where translation is completed.

What is the environment of the lysosome?

Enzymes in lysosome are known as ACID HYDROLYSES. They need acidic environment to work properly. pH inside is~5. Why is that important? Lets say one of the lysosomes burst by mistake and released all the acid hydrolysis inside the cell. They will not work properly since they are not in acidic environment. pH of cytoplasm is around 7.4 However if many lysosomes burst at the same time this will lover pH of the interior of the cell and causes apoptosis.

Tissue formation:

Eukaryotic cells can form tissues that have specific functions :)

Eukaryotic cells:

Eukaryotic cells can make up multicellular organism. Or they can exist as one cell.

Lets Look at the examples of Connective tissue: ADIPOSE TISSUE

Fat tissue that stores energy. It is exception to the rule and it does not have fibers like other connective tissue.

Where can you find Stratify Epithelial Tissue?

In places that needs to resist mechanical and chemical stress. For example esophagus.

Mitotic spindle:

In the center there are chromosomes. Chromosomes contain CENTROMERE. Outside its KINETOCHORE protein (this is the attachment point) and there are also KINETOCHORE FIBERS. Kinetochore fibers turn into INTER POLAR microtubules bc they are between 2 poles.

Lysosome:

Is a membrane bound organelle containing HYDROLYTIC enzymes that can brake down many substances. They digest/cut substances. -AUTOPHAGY means self-eating. If there are organelles in cell that are no longer functional lysosome will digest it. Macrophages of immune system will swallow pathogens then go to lysosome and they are digested by lysosome. -CRINOPHAGY this happens when lysosome digest excess secretory proteins (excess hormone). In both bases autophagy and crinophagy lysosome will release the building blocks into the cytoplasm of cell (AA) so they can be recycle.

Characteristics of the connective tissue:

It has 3 components: 1. Cells 2. Ground Substance 3. Fibers Ground Fibers and Fibers make up what is known to be MATRIX

Lets Look at the examples of Connective tissue: Blood

Its also exception and it does not contains fibers. It contains cells. The Matrix of blood is a plasma.

Lets look at the cross section of flagella or cilia:

Its made out of microtubules that are arranged in very specific way: 9+2 arrangement. Remember that this is only in eukaryotic cells. You also have protein DYENIN that brakes down ATP and uses that energy to help microtubules move pass each other and generate movement in flagella or cilia.

Lets Look at the examples of Connective tissue: HYALINE CARTILAGE

Its transparent and found in many joints. The name of the cell is CHONDROCYTES.