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UT / Biology / BIOL 230 / What is the difference between paracellular and transcellular?

What is the difference between paracellular and transcellular?

What is the difference between paracellular and transcellular?


Physiology Exam 1 Study Guide

What is the difference between paracellular and transcellular?


apical - side of the cell that faces the lumen (interior side of an organ)

basolateral - side of the cell that faces the exterior, away from organ ‘contents’ paracellular - between cells

transcellular - across cells

lumen - inside space and contents of an organ (stomach would be stomach acid and food) basement membrane - the extracellular matrix for the epithelial cells

homeostasis - maintenance of physiological equilibrium. Body’s regulation of its parameters to  keep up with a steady internal environment

negative feedback - presence of the end product reduces the rate of production of itself positive feedback - presence of the end product increases the rate of production of itself feedforward regulation - body responds in preparation of an environmental change apoptosis - programmed cell death

Define apoptosis.

If you want to learn more check out What are the stages of cell cycle?

aquaporins - membrane proteins that allow water across

rate limiting reaction - step in a process that is responsible for the rate of the entire process.  This will be the slowest step in the series

activation energy - the energy input required to make a reaction begin

end product inhibition - the product of a reaction inhibits the enzyme that created it substrate - the material that an enzyme acts upon

active site - part of an enzyme that binds to something else to make a reaction occur  ligand - binding chemical

penetrating solute - can cross the cell membrane

nonpenetrating solute - cannot cross the cell membrane

What is the energy input required to make a reaction begin?

covalent modulation - change to an enzyme that involves a chemical reaction and changes  the shape of the binding site We also discuss several other topics like How many moles are in 16.5g c? how many atoms of carbon is this?

allosteric modulation - change to a different site on the enzyme, not the binding site neurotransmitter - chemical messengers (amino acids, gasotransmitters, and monoamines) hormone - signaling molecules secreted by glands that regulate activity of organs paracrine messenger - secreted by one cell and diffused short distances to neighboring cells  to alter their behavior

autocrine messenger - secreted by a cell to trigger changes in its own behaviorIf you want to learn more check out What is the feature analysis theory and the problems associated with it?

kinase - catalyzes phosphorylation

phosphatase - enzyme that removes phosphate groups (dephosphorylyzes) saturation - concentration of a ligand in the area surrounding the active sites competition - number of different ligands that are able to readily bind to an active site transport maximum - the point where continued increase in the concentration of a substance  will no longer affect the speed of its transport across the membrane If you want to learn more check out The temperature increases by 1◦f. how much does it increase in degree celsius?
We also discuss several other topics like What makes a sample well represented?

affinity - how readily the bond between the ligand and the site forms, and how long it lasts tight junction - adjacent cells have a fused membrane on one side

gap junction - a tunnel with a gate that connects the cytoplasm of two adjacent cells desmosome - string-like protruding structures for cell adhesion to adjacent cells glycocalyx - glycoprotein coating for the cell exterior

denature - protein shape altered without disrupting any covalent bonds

degrade - protein’s primary structure is altered, so covalent bonds are broken or altered mediated transport - uniport, symport, and antiport. Transport that is controlled by a protein  integrated into the membrane

Structures and Processes:

Lipid Structure - fatty acids are the amphipathic building block for lipids. They incorporate a  long EVEN amount of Carbons with the necessary Hydrogens and on the end there is an acidic  carboxyl group. The words saturated, unsaturated, and polyunsaturated refer to hydrogen  saturation of the molecule  If you want to learn more check out What are the steps of glycolytic pathway?

• Triglycerides are a glycerol and three fatty acids, which store energy compactly. This is the  fat molecule, and it is overall non polar since the polar oxygens are encased  • Phospholipids are a glycerol, 2 fatty acids, and a phosphate. These form cell membranes • Steroids are highly lipid soluble and are chemical messengers. They building block is  cholesterol, so they are rings as opposed to a chain  

Protein Structure - built of amino acids. These are an amino group, joined with a carboxyl  group, and any of the ‘R’ residual molecules. Amino acid built molecules are referred to as  peptides. The distinction has to do with the size. Proteins are around at least 50 amino acids.  Proteins have 3D complexity, and these levels of structure are as follows:  • Primary is the pattern of amino acids, how many and in what order  

• Secondary is the general group of related sequences form what regular shape. An example  is the alpha helix, or spiral that hydrogen bonds form in DNA  

• Tertiary is the secondary structure folded onto itself due to R-group interactions  • Quantary/Quaternary comes when multiple polypeptides are intertwined

Cell Structure and Function

• cytosol - water and compounds dissolved into it

• organelles - discreet structures. Non membranous organelles include the cytoskeleton  (actin filaments) and ribosomes (free or bound to the endoplasmic reticulum). Membranous  organelles include the nucleus, mitochondria, endoplasmic reticulum, golgi body,  lysosomes, peroxisomes, and vesicles

• Smooth endoplasmic reticulum shuffles calcium in and out constantly. Short term,  manipulated calcium storage. Muscle cells have a lot of this

- This is an example of how different cells have different structures and different amounts  of organelles in order to perform their specified function.

• Vesicles can be for storage within the cell, transport to the cell exterior, or can be  specialized into lysosomes, which are vesicles that contain digestive enzymes, or  peroxisomes, which contain antioxidants to counter free radical oxygens that would  degrade our membranes and proteins

Regulation of Proteins  

• Transcriptional control - enzymes prevent or catalyze the synthesis of the mRNA copies of  DNA that code for the protein

• Translational control - enzymes prevent or catalyze the synthesis of the protein from already  existing mRNA copies

• Post translational Modification - change the activity of the protein. Some cases, turns the  protein on, while in others it turns it off

- Allosteric modification: two binding sites, regulatory (controls activity) and functional  (actual does the job the protein is intended to do). Two ligands: modulator molecule  binds to regulatory to alter shape of binding site to activate (increase affinity) or inhibit  (decrease affinity) of the controlling protein

- Covalent modulation: requires chemical reaction. another word for phosphorylation and  dephosphorylating to deactivate (two separate reactions with two different enzymes  involved)

- amount of energy involved is the most notable difference between the two. covalent  requires much more energy to make and break bonds as opposed to allosteric being  controlled by concentration of reactants and products

• Splitting: polypeptide is cut into pieces to activate or deactivate those pieces. NOT the same  as splicing, which happens to mRNA. Splitting is not reversible, meaning if you need the  original protein again, it has to be made over again

- Glycosalation & Methylation are modification as well as labeling mechanisms to help the  proteins get to the right place in the cytoplasm

• Kinds of control: Translation, splicing, transcription, post translational, degradation  - Denaturing acts on many proteins at once, so it isn't considered a control mechanism

Properties of Binding Sites: Binding of a ligand is due to the shape and charge distribution  that the correct protein folding allows for. The area where it attaches is called a Binding Site.  Changes in the environment alters the binding site and therefore can inhibit or allow attachment  of a ligand. The important characteristics of binding sites are the following:  • Affinity - measure of how readily the bond between the ligand and binding site is made and  how long it lasts  

• Specificity - exactness in match of shape and size  

• Competition - how many different ligands can readily bind to the site

• Saturation - how much of a particular ligand is available for the site  

Reaction Direction: determined by relative concentrations. A change in the concentrations from  equilibrium will result in a reaction occurring in one direction or the other

Reaction Rate: determined by the affinity of enzyme for the substrate as well as concentration  of the substrate

Enzyme Properties: All enzymes are proteins. The folding of proteins is crucial to their function.  Sometimes the folding happens automatically after formation, and sometimes helper proteins  have to hold parts in place. The correct environmental conditions are important for proper  protein shape and function. Enzymes have no direct effect on a reaction, they only affect speed.

Cellular Respiration: This is the energy transfer from ATP, and it dictates most cellular function.  Removal of a phosphate group results in a release of a large amount of energy. The three  pathways involved are Glycolysis, Kreb’s Cycle, and Oxidative Phosphorylation. Together they  are a pathway for carbohydrates, primarily glucose.

• Glycolysis: glucose is a 6 carbon sugar. It is split into two three carbon molecules. The two  3C’s can be converted into 2 pyruvate. (costs 2 ATP to make, uses 2 NAD+, but produces 2  NADH and 4ATP)

• Kreb’s Cycle: takes place in the mitochondria. Uses oxygen and converts ADP into ATP  while producing CO2 and H2O as waste products

• Oxidative Phosphorylation: electron transport chain Solute Transport

**Look up flow charts of these on the internet or in the book. I can’t include  any without violating copyright but we need to be able to draw the general  systems and identify what is used/made according to our professor**

Tonicity and Cell Shape: the osmotic pressure gradient across the membrane can effect the  shape of the cell. There are three main gradient terminologies used:

• Hypertonic - if the cell is in this type of solution, there is a higher ion concentration outside  the cell and water tends to flow out of the membrane. This makes the cell shrivel • Hypotonic - if the cell is in this type of solution, there is a higher ion concentration inside  the cell and water tends to flow into the cell, causing the cell to overflow and potentially  eventually burst

• Isotonic - ion concentration is essentially equal on both sides of the membrane. Pressure  does not favor either side of the membrane, so the cell doesn't shrivel or swell

Reflex Pathway:

• Stimuli act on Receptors, which by the Afferent Pathway send a signal to the Integrating  Center, which organizes the information and sends the appropriate instructions via the  Efferent Pathway to the Effector who creates the response  

Commonly Missed/Mixed Up: these are explained in our professor’s  study guide on Blackboard

Happy studying! I hope you found this study guide useful. This is what  I will personally be using to review for the exam, however I would also  suggest reviewing the corresponding figures for the information. Feel  free to email me with any questions!


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