Exam 1: Chapter 2: Molecules And Cells In Animal Physiology Flashcards
What are the 5 functional types of membrane proteins?
SERCT Structural proteins Enzymes Receptors Channel Transport (carrier)
What do membrane associated strucutral proteins (S in SERCT) do? Give 2 examples
Come in many different forms, but are generally cytoskeletal elements that associate with other membrane proteins to give the cell structure so that it doesn’t collapse-> EX: Microtublues and microfilaments
What are membrane associated receptors (R in SERCT) and what do they do?
They are integral membrane spanning proteins that transduce signals to inside the cell -> They generally have some hydrophilic amino acids as a part of the membrane spanning proteins
What are two examples of membrane associated channels (C in SERCT) and what do they do?
- Aquaporins: Transport water without the use of energy
- Voltage- gated sodium channel: Has 4 domains that come together to form a channel in the center which allows the passage of sodium ions
What are the two kinds of transport that transporter (carriers) (T in SERCT) aid in?
- Facilitated diffusion: Does not require energy and goes along with the concentration gradient
- Active transport: Requires energy and can go against the concentration gradient
What are three of the many forms that carbs can take?
Glycoprotein, glycolipids, and proteoglycans
Carbs are considered to be ____________ and what does this have to do with their location
Hydrophilic or water loving which is why they tend to be found on the cell- surface facing the extracellular space toward liquid
What are the three main roles of carbohydrates?
- Adhesion for extracellular proteins/ matrix: One cell to another
- Sites for cell recognition .: They aid in immunology
- Protein modification: Attachment of carbs to protein
How do carbohydrates aid in immunology and cell to cell recognition?
Immune cells have these sorts of carbohydrate tags that allow them to be recognized as self or non self by the immune system of the body
Where does glycosylation normally take place?
The golgi apparatus (sometimes in ER, but that’s v protein specific)
What organelles make up the endomembrane system and what role do they play in proteins modification?
- ER: Where folding occurs
- Golgi: Where modifications occur
- Vesiscles: How they are transported
- Nuclear membrane: Where they are targetted toward and left
How does tagging and protein modifcations work?
Carbphydrate tags are applied to proteins so that when they are put into vesicles they are targetted to a specific location based on that tag and then that tag is removed once it gets to that location
What is epithelia and where can it be found?
Epithelia are cells that cover a body surface and can be found in the inner lining of organs, vessels, and cavities
What does epithelia form a boundary between?
Between body regions and between an animal and it’s external environment
What is the apical region on generalized epithelium
The outer cells that face out from the underlying tissue into a cavity or open space
What is the basal region on generalized epithelium?
The basal cells that face toward the tissue to which the epithelium is attached and are in contact with the capillary that provides blood supply to the basal region
What is the apical region on intestinal epithelium like?
The apical region of these metabolically active cells bear microvilli/ villi that face into the intestinal lumen
What is the function of the microvilli/ villi in the apical region of the intestinal epithelium?
Provides a tremendous amout of surface area for the upper small intestine which is incredibly importnat because that is where we get the bulk of our nutrients
What is the basal region of the intestinal epithelium like?
It includes endocrine cells that produce granuals of secretory material and provides contact to the capillaries that run below it and the nutrients will enter the blood here (where we get the bulk of our nutrients from the food we absorb!)
What is unique about the itercellular spaces of intestinal epithelium?
The are particularly wide, especially toward the bases of the cells
How do venoms affect the epithelia?
Venoms contain metalloproteases that disrupt the basement/ basal membrane so it disrupts the connection between the epithelium and the capillaries, interfering with the function of the membrane itself
What are two examples of animals that use venom and one example of another toxin that work to disrupt our basement/ basal membranes and their connection to the capillaries?
- Venom: Puff adders and rattle snakes
- Cholera toxin: Disrupts the epithelia in the GI tract making it difficult for us to absorb the water from our food, causing severe dehydration
What are junctions?
They provide connections between cells
What are the 4 kinds of junctions that can occur between cells?
Tight junctions, septate junctions, desmosomes, and gap junctions
What is a desmosome and what is their function?
A desmosome is a localized spot where glycoprotein filaments between two cells bind to each other, causing the contact between cells to be strengthened and they function in cell adhesion, in the ECM, and in the communication between cells
What are gap junctions and what do they do?
They are pores composed of as many as 6 receptor like connexin proteins. They are present in both the cells and the two cells will connect to generate channels that allow the passage of small ions (less than 1500 Da), but not large prtoeins. Essentially, they are localized spots where the cytoplasms of two cells communicate through tiny pores. They are important for the connections and cell to cell communication between nerve and muscle cells
Why are gap junctions important in the heart?
They allow for the heart cells to communicate with each other not only for the movement of ions, but alos electrophysiology and signlaing
What is another name for “occluding junctions”
Tight and septate junctions
What is another name for a “spot weld” junction?
Desmosomes
What is another name for a “communicating junction”?
A gap junction
How do tight and septate junctions work?
They occlude the intercellular space between the two cells by not only meeting cell membranes/ fusing at such junctions, but also by the junctions forming continuous bands around the cells
What are unqiue about tight junctions vs septate junctions?
In tight junctions, the cell membranes of the two cells make contact at ridges and they can be found below the microvilli on epithelial cells in the GI tract
How can metabolism be defined?
As the chemical and physical processes in cells and organisms that sustain life
What two pathways can metabolism be divided into?
Catabolism and anabolism
What is an example of metabolism?
Both the catabolism and anabolism of glucose
How many reactions are involved in the oxidation of glucose?
Between glycolysis, the prepatory step (Acetyl CoA), the Kreb’s cycle, and the ETC, you have about 30 different reactions and many enzymes invovled in each of those
Cells direct genes to make what?
Enzymes that allow reactions to occur
How do enzymes work?
They lower reaction energies AKA the energy of activation and reaction speeds and sometimes even help catalyze reactions that wouldn’t normally happen otherwise
What does an enzyme always require?
A substrate and the generation of a product as the end point of the reaction
What two kinds of kinetics can reactions have?
Hyperbolic or sigmoid kinetics
Hyperbolic enzyme reactions use what kind of kinetics model?
Michaelis- Menten kinetics
What determines the kind of kinetics an enzyme uses?
The chemical properties of that enzyme
Explain steps 1,2, and 3 on this hyperbolic kinetics curve
1) / 2) The reaction velocity increases because of the increased availability of substrate, which allows for a greater fraction of enyzmes to engage in catalysis at any given time
3) Substrate levels are so abundant that all enzyme molecules are already saturated, so the reaction velocity cant increase anymore
What happens at Vmax on a enzyme kinetics curve?
All enzyme sites have been filled by substrate
Which image shows hyperbolic kinetics and which one shows sigmoid kinetics
Left: Hyperbolic kinetics
Right: Sigmoid kinetics
How would the enzyme kinetics change if there was an infinite amount of substrate vs a limited amount of substrate?
- Infinite amount of substrate: Rxn would go on forever becuase enzymes are recycleable .: They can be used over and over again and generally aren’t broke down unless there is a reason for them to be broken donw
- Limited amount of substrate: Rxn will not go on forever
What is the energy of activation and how does it change with catalysis
The energy required to achieve the transition state
- W/ catalysis the energy of activation is lower making the rxn much faster (less of an uphill fight) - W/o catalysis the energy of activation is much higher making it harder for the rxn to occur
What is the success of a raction related to?
The affinity of the substrate to the enzyme
The higher the affinity an enzyme has for a substrate, the ________ Km will be. How does this affect the velocity of the reaction?
The higher the affinity an enzyme has for its substrate, the lower Km will be. This gives the enzyme and substrate a greater chance of forming a complex, which affects the veolckity of the reaction because the enzyme/reaction will reach saturation faster
What is the Km?
The substrate concentration at 1/2 Vmax
Which way will the line of a high- affinity enzyme shift on a graph and what does this mean for the Km? Which way will the line of a low- affinity enzyme shift on a graph and what does this mean for the Km?
- A high affinity enzyme will reach saturation faster AKA it will have a lower Km, meaning the line will be shifted to the left to indicate a lower substrate concentration at 1/2 Vmax -> (it takes less substrate and time for the rxn to reach 1/2 Vmax)
- A low affinity enzyme will reach saturation slower AKA it will have higher Km, menaing the line will be shifted to the left to indicate a higher substrate concentration at 1/2 Vmax -> (it takes more susbtrate and more time for the rxn to reach 1/2 Vmax)
Complicated proteins have what kind of structure?
Complex, tertiary, and 3D structure
The 3D structure of a protein depends on what?
H-bonds, van der waals interactions and hydrophobic interactions
What kinds of bonds help hold alpha- helices and beta pleated sheets together and antisense/ sense DNA together?
H-bonds
After a substrate binds to its enzyme, what happens?
A conformational change occurs that allows the enzyme to better hold and bind to its substrate
What is cooperativity?
The interactions between multiple binidng sites within the binding of a ligand
Explain how hemoglobin exhibits cooperativity
When hemoglobin binds 1,2,3, or 4 oxygen moelcules, it changes its strucutre to better be able to hold those oxygen molecules and deliver them to sites where those oxygen molecules are needed like picking up oxygen in the lungs and delivering it to the capillary beds
When does hemoglobin exhibit the most cooperativity? The least cooperativity?
It exhibits the most cooperativity when it has 4 oxygen molecules bound and the least cooperativity when it has 1 oxygen molecule bound
What structure would exhibit more cooperativity, oxyhemoglobin or deoxyhemoglobin?
Oxyhemoglobin
Cooperativity can take what two forms?
Positive or negative
What is allosteric activity?
The change in configuration with the binding of a ligand or substrate AKA a type of cooperativity that effects an enzymes catalytic activity, leading to either activation or inhibition
What is an example of an allosteric modification?
Phosphorylations to proteins which result in activation
The structure/ function of an enzyme depends on what? What is this called?
The structure of an enzyme depends on their function/ location in the body. These enzymes are called isozymes or interspecific enzyme homologs
What is an example of an enzyme that has major isozymes/ specific enzyme homologs?
Lactase dehydrogenase
All metabolic pathways are run by what?
ENZYMES:)
What determiens the kind of enzyme and amount that will run a metabolic pathway?
Gene epxression via gene regulatory elements and transcription factors to either up or down regulate enzymes
What does it mean if an enzyme is consitutively expressed?
That it’s on all the time
What does it mean if an enzyme is inducible?
That the enzyme is not on all the time and must be turned on or induced to work
What is an example of an inducible enzyme?
P450
What does P450 do?
It an inducible enzyme that works as a detoxifier/ antioxidant to pollulatants and it almost works like an immune system so if we were exposed to something like a barbituate, upon the 2nd exposure, P450 will work to negate the effects of that 2nd exposure (but it wouldn’t work unless you had a previous exposure!)
What does allosteric modulation allow for? How does this affect a whole pathway and what can it lead to
Upregulation or down regulation of enzymes as cellular needs requires, which can effect entire pathways and lead to things like feedback or end-product inhibition
Explain how in glycolysis, phosphofructose is an allosterically modulated enzyme
- When citrate binds according to mass action with its regulatory site, it decreases the catalytic acativity of phosphofructokinase
- When AMP binds it potently increases the catalytic activity of phosphofructokinase
What are two examples of covalent modification to enzymes?
Phosphorylation and dephosphorylation
What does phosphorylation generally result in?
Activiation
What catalyzes phsophorylation?
Protein kinases
What do protein kinases do?
They catalyze phosphorylation and often function in multi-enzyme sequences that bring about amplifying effects
If a protein kinase catalyzes phosphorylation during second messenger activity, it can result in what?
Amplification
What are the roles of molecular chaperones?
They can work 1 of two ways when they are upregualted during times of cellular stress:
1) Complete denaturization: Target denatured proteins for complete denaturization or degradation 2) Renaturization: Repair denatured proteins
What is an example of a molecular chaperone?
Heat shock proteins, which are upregulated and inducible during times of cellular stress
What pathway is used for the degradation of proteins and how does it work>
The ubiquitin- proteosome degradation pathway: It tags proteins by covalently modifying them and deactivates/ destroys those proteins that have been tagged
How does cellular reception and the use of signals work?
When a signal arrives at a cell, there msut be a mechanism for receiving and transducing that signal: Receptors on the extracellular surface bind ligands, which cause a change in the molecular conformation of the receptor, setting in motion further events and signal transduction within the cell
What are three examples of how the body uses signals?
1) Allows cells to communicate and activate organs
2) Allows us to form memories
3) We use it to respond to sensnory stimuli
How many classes of receptors are there?
4
How many of the different types of receptros are found on the cell surface?
All, but one
What are the 4 different classes of receptors?
1) Ligand- gated channels
2) G- protein coupled receptor and associated G protein system
3) Enzyme/ enzyme linked receptor
4) Intracellular receptor
Why do enzymes have some felxibility in their structure?
Because not all the bonds are covalent, some are weak bonds that allow flexibility in the structure. This is key to enzyme function and allows for conformational shape changes when binding substrates
What happens when you heat up DNA to about 95 degrees Celcius in terms of bonds? What hahepns when you cool it back down?
When you heat up the DNA the H-bonds break causing the DNA to lose its teritary structure and seperate the two strands and when you cool it back down it allows the DNA to rehydridize
How can you break the back bone of DNA? Can you do it by heating?
No, unlike the H-bonds that hold the two strands of DNA and the tertiary strucutre together, enzymes are needed to break the actual backbone of DNA
Are hydrogen bonds stronger than covalent bonds?
No, hydrogen bonds are weaker than covalent bonds, but if you have a lot of them they can be pretty strong
Explain how a fish- hunting cone snail works against its prey
How many different sites of amplication are there and what are they?
There are 4 differnt sites of amplification where multiple protein products are potenitally generated:
1) First with G protein activation 2) Adenylate cyclase role 3) 2 different kinases
A number of second messenger pathways result in cell signal transduction, what are the 5 second messengers?
DICCC:
- DAG - IP3 - cAMP - cGMP - Ca2+: Intracellular calcium, which is important in the activation of muscle cells
