(cytology) lab exam #2

Define cytology

• the study of the structure and function of cells

Define cell

• structural and functional unit of life

Describe the three main parts of a cell

• plasma membrane: flexible outer boundary

• Cytoplasm: intracellular fluid containing organelles

• Nucleus: control center

Describe the structure and function of the plasma membrane

• structure

  75% phospholipid bi-layer. The phospholipids have a hydrophobic phosphate head, while the other end has a fatty acid hydrophilic tail. These structures line up and face each other. Tails facing in on each other and the head facing out. This helps keep things within in and outside the cell

5% glycolipids. These lipids ,glycocalyx, are found in the outer surface of the phospholipid bilayer and act as a cells id due to the uniqueness of each sugar. Every cell has its own glycocalyx sugar protein

20% cholesterol this helps increase the membranes fluidity

Membrane proteins: these proteins allow the cell to communicate with its enviorment. There are two types. Integral proteins are embedded into the membrane and have both hydrophobic and hydrophilic regions, helping them interact with both the heads and tails of the membrane. Peripheral proteins are loosely attached to the integral proteins (glycocalyx). these membranous proteins work together to

• transport

• Receptors for signal transduction

• Attachment cites

• Enzymatic

• Intercellular joining

• Cell to cell recognition

Describe the structure and function of tight junctions

Location:

• tight junctions are located in the superior inter cellular space region

Function

• interlocking impermeable junction, meaning it doesn’t allow substances in without the cells approval

Describe the structure and function of Desmosomes

Location:

• located within the mid lateral portion of the intercellular space

Structure

• It starts of with linker proteins within the intercellular matrix that connect the two different cells. Then connected to the linker proteins is a plaque that contains intermediate filaments (myofilament).

Function:

• working together, the filaments reaches across the entire cell and connects to other desmosomes that are doing the same think in the opposite direction.

• it anchors the cells together, acting as a Velcro. This reduces tension and cell separation.

Describe the structure and function of Gap Juction

Location

• interior lateral wall within intercellular space, near the stratum basale

Stucture

• channel between cells formed by connexons

Structure:

• create a pathway through the channel, in turn allowing ions and small molecules to pass, creating a way for communication between other cells

State the requirements for passive mechanisms of transport across plasma membrane.  

• no cellular energy is needed

• Substance move down it’s concentration gradient

State the requirements for active mechanisms of transport across plasma membrane.  

• energy, atp is required, therefore only occurs in living membranes

Diffusion

Passive process bc it requires not atp and requires a concentration gradient

Simple diffusion

• when a fat soluble (lipid soluble) molecule move directly through the plasma membrane

- o2 going in the cell, co2 coming out

Carrier mediated facilitated diffusion

• Chemical specific transport proteins carry lipid insoluble proteins across the membrane and change shape once binding and releasing the solute

Channel mediated facilitated diffusion

• Channel proteins process pathway for lipid insoluble substances to move through the membrane

• The substance has to be small enough to pass through the Chanel and have a concentration gradient

Osmosis

• Passive process bc it doesn’t require atp and it need a concentration gradient

  
  

• Osmosis concerns the movement of a solvent moving down its concentration gradient.

• The solvent water always moves to where there’s less water. The water moves through specific Aquaporin channel proteins

  it also get writhing the cell when the membrane shifts from left to right

• Osmosis is dependent on osmolarity: concentration of a solution (expressed by the numbers of solutes)/ liters of solutes

  basically how much of solutes/solvant, we want equilibrium

• During osmosis, both water and solutes move interchangeably to make it balanced

Types of osmosis

Tonicity: the ability of a solution to alter cells water volume

• isotonic: solution with the same non-penetrating solute concentration on both the inside and outside the cell

  meaning: cell will keep the same shape

• hypertonic: solution with higher concentration of non penetrating solutes out side the cell

  meaning the cell will shrink due to osmosis moving down its concentration gradient (from within the cell to the outside)

• Hypotonic: solution with lower concentration of non penetrating solutes that the cytosol

  the water diffuses into the cell meaning it’ll expand

i. primary active transport, secondary active transport

Active transport

Transports small proteins

Example sodium potassium pump

Primary active transport

• the transport protein removes sodium against its concentration gradient from the cell and uses atp to do that

• With sodium going in potassium enters the cells

Secondary Active transport

• the cotransporter protein does not need atp in order to atp to function.

• Primary active transport creates a concentration gradient of sodium, meaning it’ll need to move back into the cell

• When the cotransporter protein moves sodium down its concentration gradient glucose moves against its concentration gradient down the protein

***glucose needed the sodium concentration first in order to get in the cell

endocytosis

Types: (phagocytosis, pinocytosis, and receptor-mediated endocytosis)

Active transport

Endocytoys: to be moved into the cell

phagocytosis

• membrane engulf a large particles by projecting pseudopods and enclosing with whiting the the membrane sac known as a phagosome

pinocytosis

• The cellular membrane takes gulps of extracellular fluid that contains solutes

receptor-mediated endocytosis

• extracellular solutes bind to protein receptors along the cellular membrane. The receptors create an invagination and either release directly into the cells or into a lysosome in order to be digested

iii. transcytosis

• transports into, across and then out of the cell

iv. exocytosis

• activated by change in cellular membrane voltage or cell surface signal

• Substances are enclosed within a secretory vesicle and transported outside of the cell

v. vesicular trafficking

• transported form one area or organelle of the cell to another

Sodium potassium pump

• the cell is most happy when there’s more sodium outside the cell than inside the cell,and when there’s more potassium inside the cell than out side the cell

• Within the cell membrane are sodium and potassium channels. The channels allow for slow leakage of sodium and potassium down their concentration gradient, trying to reach equilibrium.

• the cell doesn’t want equilibrium. Sodium potassium pumps allow for sodium and potassium to move against their potassium gradient. This works against the channels and allows for potassium to leak within the cell and sodium to leak out

nucleus

• found within the cells and acts as a gen ethic library that contains blueprints for all cellular proteins

• Responds to signals and dictates the kinds and amount of proteins being synthesized

ribosomes

• granules containing proteins and rRNA

• Synthesizes proteins

• Free ribosomes synthesize protein for the cytosol or other organelles

• Membrane bound ribosomes(rough endoplasmic reticulum) synthesize proteins that can be incorporated into the cell membrane or exported from the cell

endoplasmic reticulum (smooth and rough)

• continues with the nuclear envelope and for a complex interconnected tubes and parallel membrane enclosing cisterns

Rough

• studded with ribosomes

• manufactures: secreted proteins, membrane integral proteins and lysosomal enzymes

• Proteins are enclosed within a vesicle and move to the interior of the er and head to the Golgi apparatus

smooth

• Has enzyme integral proteins that function in

  lipid metabolism

  detoxification

  converting glycogen into free glucose

• Storage and release of calcium

Golgi apparatus

• stacked, flattened and curved membranous sacs

• Modifies, concentrates and Packages proteins from the rough er

mitochondria

• double membranous structure with inner shelf like cristae. Contain their own dna

• Produces the cells atp

lysosomes

Spherical membranous vesicles containing acidic digestive fluids

• degrades substances bacteria,viruses and nonfunctional organelles

• Breakdown glycogen

• Destroy cells for injured or non useful tissue

• Break down bone to release calcium

• Components are recycled

peroxisomes

• membranous sacs containing powerful oxidases and catalases

• Detoxifies harmful or toxic substances

cytoskeleton

Structures

• microfilaments

  actin

• Intermediate filaments

• microtubules

Function

• change cells shape

• Control internal tension

• Maintain shape of the cell

RMP

• resting membrane potential is established by the electrical potential energy produced by the separation of ions across the plasm membrane.

• The difference is refers to as a voltages and cells with a charge are polarized

Example:

• negetivly charged proteins cannot leave the membrane, make the internal structure negetive

• Potassium is positive and leaves the cell through potassium leakage channels . With more +’s on the out side and negatives on the inside the cell becomes more negetive due to the lack of positive

• Once enough potassium leaves, the cell become so negative that the positive potassium become attracted to the negetive cell and leaks back into the cell

• When the opposite charges forces become balanced the cellular plasma membrane establishes a resting membrane potential (90mV)

• The difference allows for electrochemical gradient to be present allowing for electrical signals to be sent and recieved

centrioles

• tubes formed by microtubules

• For the basis for cilllia and flagella

centrioles

• tubes formed by microtubules

• For the basis for cilllia and flagella

Cillia, flagella, microvillus

Cillia

• on surface of the cell, needs motor pattern in order to move

• Move substances across the cells membrane

Flagella

• surface of the cell

• Long and propels the entire cell forward (sperm)

Microvillus

• finer like projections of the plasma membrane

• Increase surface area for absorption

  
  

Transcription

Taking the code of dna into mRNA

Translation

rRNA is read by the ribosome in order to make proteins