[2.1] THE Cytoplasm PART 1 PDF

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LESSON 2WEEK 1 | August 13, 2021THE CYTOPLASM (PART 1)PARTS OF HUMAN CELL1. MEMBRANE Boundary/border of human cell 2. CYTOPLASM  Space inside the human cell  Area between the membrane and the nucleus (encompasses everything [all the contents] inside the cell membrane except for nucleus)  Fluid p...

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MLS 407 – HISTOLOGY (LECTURE) LESSON 2 WEEK 1 | August 13, 2021

THE CYTOPLASM (PART 1) PARTS OF HUMAN CELL

IN REALITY…

1. MEMBRANE  Boundary/border of human cell 2. CYTOPLASM  Space inside the human cell  Area between the membrane and the nucleus (encompasses everything [all the contents] inside the cell membrane except for nucleus)  Fluid portion of the human cell 3. NUCLEUS  Largest organelle of the cell and most of the time situated in the center, but in some cells, it is located in the periphery (boundary or edge)  Often represented as circular figure in drawings 4. NUCLEOLUS  Another circular figure represented in the human cell but situated inside the nucleus 5. OTHER ORGANELLES  Functional solid structures found in the cytoplasm of the human cell  Act like organs in the body but are smaller so are called organelles 6. CYTOSOL  Where the organelles are suspended  Fluid inside the cell; mostly water (fluid everything inside the cell moves around in)  Part of cytoplasm

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In an actual specimen under a microscope, only prominent structures and parts are seen The actual picture is usually seen through a bright-field type or COMPOUND MICROSCOPE (commonly used type of microscope in Histology Lab) In the cytoplasm, you can’t see the organelles but a void only

CYTOPLASM     

Organelles (solid) + cytosol (fluid) Contains both solid and fluid portions of the cell Solid structures outside the nucleus are called ORGANELLES Fluid where the organelles are suspended is called CYTOSOL According to some books, cytoplasm doesn’t just include the organelles and cytosol, but it also includes a 3rd component called INCLUSION BODIES

CELLS 

Composed of three basic parts:  Cell membrane  Nucleus  Cytoplasm  Solid portion = organelles  Fluid portion = cytosol

INCLUSION BODIES 

Inclusion bodies, like the organelles, are solid

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MLS 407 – HISTOLOGY (LECTURE)

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Not a functional organelle (unlike the organelles which have functions) May or may not be present in the cell Most are stored nutrients or cell/waste products (at some point in the life of the cell they might be present or disappear) Ex. Stressed with acads  eat a lot of food  buildup of fats in the body  the fats will be deposited in hepatocytes (liver cells)  cytoplasm of hepatocytes will have solid components that were not present before  now referred as inclusion bodies Not called true organelle because they don’t contribute any function to the cell Examples are lipofuscin, lipid, glycogen, etc.

1. LIPOFUSCIN

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Yellow-brown pigment (using H&E staining) composed of residues of lysosomal digestion Accumulates through the years (gives the idea how old the cells are)

More lipofuscin = OLDER

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Organelle situated in the center is the LYSOSOME It is the unique organelle that contains digestive enzymes which plays a big role in intracellular digestion Cells can breakdown fats, lipids, and carbohydrates which take place in the lysosome Lysosome does not only digest fats, lipids, and carbohydrates. Ex. It plays a role when there is an injury wherein organelles can become damaged which can compromise its normal functioning  The cell will discard the damaged organelles which is transported to the lysosome, and it digests the organelle  As the lysosome is digesting fats, lipids, carbohydrates, and damaged organelles, the accumulated waste products of the digestion in the lysosome is the LIPOFUSCIN

Less lipofuscin = YOUNGER

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“Wear and Tear” pigment = cellular senescence or aging

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If the cell with the lipofuscin undergoes mitosis, the 2 daughter cell will no longer contain lipofuscin. As the cell undergoes mitosis, the lipofuscin disappears. Aside from the fact that lipofuscin indicates the age of the cell, it has the tendency to accumulate in cells that are not actively undergoing mitosis.

SITUATIONAL EXAMPLE!  Once neurons are lost in stroke, it can’t be replaced.

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MLS 407 – HISTOLOGY (LECTURE)

LESSON 2 WEEK 1 | August 13, 2021  

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When there is an injury on the skin, fibroblasts and keratinocytes will multiply in number just to replace damaged tissue. Neuron has a limited capacity to multiply, and the fibroblasts and keratinocytes in the skin has unlimited capacity to multiply, then the accumulated lipofuscin in fibroblasts and keratinocytes will disappear since it can undergo mitosis and the neurons can accumulate lipofuscin since it can’t undergo mitosis.

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Process shown is how we convert glucose to ATP, but sometimes we tend to overeat, so we supply our body with glucose above the requirement of our body:

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Insulin facilitates in the storage of glucose (GLYCOGEN) and not discarded through urine Glycogen is the storage form of glucose Stored in skeletal muscles and liver NOT STAINED with H&E; appears like clear areas Requires special stain for carbohydrates such as periodic acid Schiff (red in color)

Lipofuscin is best demonstrated in organs or cells that are inactively undergoing mitosis, so they are present in postmitotic cells such as nerve, skeletal muscles, and cardiac muscles (still can undergo mitosis but in a very slow pace).

LIPOFUSCIN IN BRAIN

   LIPOFUSCIN IN MYOCARDIOCYTES

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2. GLYCOGEN

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Glucose enters the cell  undergoes glycolysis in the cytoplasm and its product are 2 pyruvate molecules  pyruvate enters the mitochondria  converted to Acetyl Coenzyme A (CoA)  Acetyl CoA participates in the Krebs Cycle  products of Krebs Cycle are transported to the inner mitochondrial membrane and proceeds for the electron transport chain  ATP

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Excessive glucose intake from eating may make the glycogen storage more prominent in hepatocytes under a microscope

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MLS 407 – HISTOLOGY (LECTURE)

LESSON 2 WEEK 1 | August 13, 2021

is why the sperm is alkaline so the lactic acid in the vagina will not kill it)

STAINED WITH PERIODIC ACID SCHIFF

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Glycogen granules can also be found in the lining epithelium cytoplasm of the vagina for another purpose but not for energy storage

Glycogen in vagina is acted upon by the bacteria present in the vagina which are the normal flora (Lactobacillus acidophilus), and this normal flora converts glycogen to lactic acid making the vaginal environment acidic which inhibits the growth of microorganisms and protecting the vagina from infection (that

3. HEMOSIDERIN  Appears as a brownish pigment  Indigestible residue (breakdown product) of hemoglobin  Can be normally found in the red pulp of the spleen (graveyard of red blood cells if >120 days old)  Often results from bleeding when red cells and hemoglobin are degraded by macrophages  Alveolar macrophage if there are hemorrhages in the alveoli  Appears as brown granules

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Spleen appears to have white and red pulp  White pulp is rich in lymphocytes, appears to be nodular or rounded in shape, and surrounded by the red pulp  Red pulp is where the damaged red blood cells are destroyed

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Splenic sinuses are the spaces within the red pulp where the erythrocytes flow, but these sinuses are too small so the erythrocytes have to be flexible in order to successfully flow within the sinuses The damaged and old red blood cells will most likely lose its flexibility so they get trapped within the sinuses and get eaten

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MLS 407 – HISTOLOGY (LECTURE)

LESSON 2 WEEK 1 | August 13, 2021

by macrophages (present in splenic cords)  the erythrocytes get destroyed  hemoglobin of the red blood cells will get degraded  there will be a formation of hemosiderin

NORMAL HISTOLOGY RBCs

ALVEOLI W/

NORMAL HISTOLOGY MACROPHAGE EATS RBC

HEMOSIDERIN IN ALVEOLAR MACROPHAGES

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Hemosiderin is normally found in the red pulp of the spleen, but it can also be present in areas where there is hemorrhage or bleeding Ex. In the alveoli (terminal portion) of the lungs with Mycobacterium tuberculosis  there is destruction of the walls of alveoli  there is bleeding  spaces of alveoli will have erythrocytes present and affect gas exchange (difficulty breathing)  there is a need for the body to remove RBCs in the alveolar space to restore normal gas exchange function of the lung  alveolar macrophage needs to clear up the RBCs in the alveolar spaces  macrophages will engulf RBCs and digest it  hemoglobin in RBC is converted to hemosiderin

4. LIPIDS  Commonly deposited in ADIPOSE CELLS / TISSUE  Accumulates thru time in adipocytes displacing all organelles and nucleus into periphery  Extracted by solvents during tissue preparation (clearing and dyhydration), thus appears “hole in the cytoplasm” (before the preparation, it previously has fats inside)

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MLS 407 – HISTOLOGY (LECTURE)

LESSON 2 WEEK 1 | August 13, 2021

CELL MEMBRANE   

Outermost boundary / border of the cell Regulates passage of molecules in and out of the cell Bilipid (2 layers of phospholipid) layer

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5. MELANIN  It is found on the basal layer (stratum basale) of the epidermis  A pigment responsible for the brown color of the skin

Cell membrane components:  PHOSPHOLIPIDS  Look like balloons  Most abundant component  CHOLESTEROL  Inserted among the phospholipids  PROTEIN  Large appearing structures of the cell  CARBOHYDRATE  Component always displayed outside

PHOSPHOLIPIDS 

The 2 layers of phospholipids are made up of head and tails  HEAD = PHOSPHATE = HYDROPHYLIC (Yes H O) = POLAR  TAIL = 2 TY ACIDS = HYDROPHOBIC (No H2O) = NON-PO

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MLS 407 – HISTOLOGY (LECTURE)

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COMMON KNOWLEDGE: Glucose will never enter the human cell without the presence of insulin If insulin is absent, glucose will remain in the blood and it will cause hyperglycemia wherein the patient will be diagnosed with diabetes mellitus

CHOLESTEROL   

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When a substance has both hydrophilic and hydrophobic portions, it is described as AMPHIPATHIC How are the phospholipids arranged in the bilipid layer?  Since outside the cell and cytosol within the cell are rich in water, thereby the phospholipids are arranged in such a way that the hydrophilic portions are facing the water  The hydrophobic tails, fatty acid tails, are situated in between the heads and hidden from the water

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Do you know that phospholipids tend to migrate from one place to the other? Whenever insulin is present, they bind to the [yellow] insulin receptor proteins and they respond by causing the [blue] glucose transporter to open; when the GLUT4 is open, the glucose molecules are now free to enter the cell and now undergoes glycolysis

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What if the membrane is highly fluid? Phospholipids are allowed to migrate to different sites in the cell membrane There is a tendency that the phospholipids will drag along (change the location) with them the components that are found beside them When the glucose transporter, for example, is moved, the glucose molecules will now have no entry point and the glucose will remain in the blood causing hyperglycemia so the CHOLESTEROL functions to hold them in place Cholesterol has hydrophobic ring and hydrophilic hydroxyl group

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Cholesterol is inserted among closely packed phospholipids restricting their movements and thus modulating fluidity and movement of membrane components

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The hydrophobic rings of the cholesterol are also called perhydrocyclopentanophenanthrene ring

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The hydroxyl group in the terminal part is hydrophilic  Since it has both hydrophobic and hydrophilic portions, it is amphipathic  How is cholesterol arranged in the cell membrane?  The hydroxy group, hydrophilic, it is located at the area where you can find the phosphate heads of the phospholipids which are also hydrophilic  While mixed along with the hydrophobic fatty acid tail is the four-fused ring of the cholesterol LIPID RAFT  Localized region within the plasma membrane that contains high levels of cholesterol and variety of peripheral and integral proteins  Area is limited in fluidity thus restricting movement of the proteins which may be involved in cell signaling processes 

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The lavender chemical interacted with the G protein receptor and activated the blue protein to activate the Adenylate cyclase and reacts to the presence of the lavender chemical outside, so the cholesterol is important to keep the receptor in place to make the process successful

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Lipid rafts as SIGNALING PLATFORMS:  G-coupled protein composed of 7 transmembrane proteins and alpha, beta, and gamma protein subunits  Ligands bind to the G-coupled receptor which later cause the activation of the alpha, beta, and gamma subunits  Signal transduction in lipid rafts occurs more rapidly since proteins are found in proximity to each other

There are chemicals that can make cells react by binding to the receptor. One importance of a lipid raft is for a receptor to be formed, the proteins must be close to each other and not moving apart. Another is the lipid raft can activate other proteins within its viscinity

PROTEINS  

It can be divided into: INTEGRAL (transmembrane) PROTEINS  Directly incorporated into the cell membrane

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MLS 407 – HISTOLOGY (LECTURE)

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Channels, carriers, transporters, and even as receptors PERIPHERAL PROTEINS  Exhibits looser association with one of the membranes  Easily extracted from the membrane  Responsible for the shape of the cell (maintains the integrity of the cell) and transport of the substances within the cell 

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Ex. The peripheral proteins bind together and pulls each other creating a concaved shaped of the cell membrane = RBCs  so concludes that peripheral proteins help maintains

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Developed to study the integral proteins present in cell membrane Cells are exposed to freezing temperatures  strike a force using a hammer  cause the membrane to be fractured (usually created in the hydrophobic portion of the cell membrane, fatty acids)  membrane is separated into 2 layers (extracellular and cytoplasmic)  cell membranes are viewed under ELECTRON MICROSCOPE They saw protrusions on the extracellular and cytoplasmic layers caused by the presence of integral proteins For every protrusion on the extracellular layer, there is a corresponding depression on the cytoplasmic layer of the cell membrane

DID YOU KNOW? Hereditary spherocytosis is a condition where people are born without the genes for spectrin (absence of spectrin) making ankyrin and actin not bind with each other resulting to the red blood cell losing its biconcave shape. The spherical shape of the RBC makes it harder for it to squeeze through smaller capillaries making the spherical RBCs get destroyed [rupture] in the circulation. Later on, the people with hereditary spherocytosis develop anemia.

CARBOHYDRATES   

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Can be glycolipids or glycoproteins Generally found outside the cell membrane May act as receptors that participate in CELL ADHESION, and CELL-TO-CELL INTERACTION

FREEZE FRACTURE MODEL of the cell membrane

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MLS 407 – HISTOLOGY (LECTURE)

LESSON 2 WEEK 1 | August 13, 2021

cells of the blood vessels so it will not get carried away by the tremendous pressure from the flowing blood. 2. CELL-TO-CELL INTERACTION

1. CELL ADHESION  Majority of the white blood cells are circulating in the central portion of the blood vessel lumen, and the red blood cells on the periphery  Red blood cells need to share oxygen to the cells and pick-up carbon dioxide

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Majority of the white blood cells are on the central portion to not interfere, but when there is an infection, leukocytes have to go to the margin of the vessel  go out  go to the infected part of the body

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[CHEMOTAXIS]: The polymorphonuclear (PMN) neutrophils have glycosaminoglycans (carbohydrates = glycolipids and glycoproteins) on its cell membrane and it uses it to attract to the glycosaminoglycans on the endothelial

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PASSIVE TRANSPORT 

Can be…  Simple (WITHOUT the help, directly across)  Facilitated (WITH the help of channels or carrier)

QUESTIONS 1. Requires energy?  Active Transport 2. Oxygen and carbon dioxide diffusing across the membrane via ________?  Simple Passive Transport 3. Transport of molecules is against concentration gradient?  Active Transport 4. Transport of molecule is from higher to lower concentration and requires carrier or channel?  Facilitated Passive Transport   

From HIGHER TO LOWER concentration No energy consumption for molecules to move Channel VS Carrier?  Channel allows the transport without changing its shape  Carrier allows the transport by modifying its shape

ACTIVE TRANSPORT  

Requires energy consumption (using the ATP) Pumps transport molecules from LOWER TO HIGHER concentration (against concentration gradient)

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