M3 L1 Flashcards
(93 cards)
1
Q
Whats the purpose of the cell membrane?
A
- keep toxic substances out of the cell
- contains receptors that mediate what passes through (such as ions, nutrients, waste, etc)
- separate metabolic processes conducted within organelles
2
Q
What is the cell membrane made up of?
A
lipids and proteins
3
Q
What is the purpose of proteins in the cell membrane?
A
Serve as carriers, channels, receptors, and enzymes.
also allow for the passage of ions through the membrane (bc the membrane itself doesn’t let them pass)
4
Q
What are phospholipids
A
type of lipid (fat molecule) that are a major component of cell membranes.
have hydrophilic and hydrophobic components. they form the plasma membrane
5
Q
what forms the plasma membrane
A
phospholipids
6
Q
What struggles to get across the bilayer?
A
- charged molecules
- large size
7
Q
What are lipids
A
molecules that are insoluble in water bc they’re non polar - they will aggregate in aqueous solution to form bilayer with a hydrophobic center
8
Q
What are the three main types of membrane lipids?
A
Phospholipids, sphingolipids, and sterols
9
Q
Lipids: Phospholipids
A
10
Q
What is the most abundant lipid in the membrane?
A
Phospholipids
11
Q
What is phosphatidylcholine?
A
A modified triglyceride and a common phospholipid in membranes
12
Q
Are phospholipids amphipathic? What does that mean?
A
Yes, they are amphipathic—they have both hydrophilic (water-loving) and hydrophobic (water-fearing) parts
13
Q
What is sphingomyelin and what is its role?
A
A type of sphingolipid important for producing myelin (insulates nerve cells)
14
Q
What are sterols and what is an example?
A
Non-polar lipids like cholesterol
15
Q
What role does cholesterol play in the membrane?
A
can make membrane more fluid or rigid - depends on temp/environment
16
Q
what do the intestinal epithelial cells do?
A
form a barrier between the inside of your body and the contents of your intestines (which is technically “outside” the body)
protection of the human body from microbial infections in gut
17
Q
what is intestinal lining is made of
A
epithelial cells (flat, tightly packed cells).
18
Q
What do tight junctions do in the intestinal epithelium?
A
They form impermeable seals between cells to block unregulated movement of material.
19
Q
Where are tight junctions located in epithelial cells?
A
On the lateral edges (sides) where two cells meet.
20
Q
Why is it important that materials can’t move freely between epithelial cells?
A
To prevent harmful substances from entering the body unregulated.
21
Q
How do tight junctions regulate what enters the body?
A
By forcing materials to pass through the cells, where they can be filtered.
22
Q
What is the apical surface of an epithelial cell?
A
The top side facing the lumen (e.g., inside of the intestine).
23
Q
What are microvilli and what do
A
structures are found on the apical surface that increase surface area
24
Q
Why is increased surface area important in epithelial cells?
A
It enhances absorption of nutrients or other substances.
25
What is the basal (serosal) surface of an epithelial cell?
The bottom side that sits on the basement membrane (ECM).
26
What is the ECM (extracellular matrix)?
A 3D meshwork of proteins that supports and anchors cells.
27
What are tight junctions and where are they located?
Tight junctions (zona occludens) are located at the apical surface of epithelial and endothelial cells and seal cells together.
28
What is the function of tight junctions in epithelial cells?
They prevent leakage between cells and maintain cell polarity.
29
What are cell-cell junctions
These are structures that connect adjacent epithelial cells together and help maintain the barrier and communication.
30
What are the two roles of tight junctions?
Protective barrier and functional barrier (e.g., transport and osmotic balance)
31
What do tight junctions form and what do they do?
Form a multiprotein junctional complexes whose function is to prevent leakage of solutes and water and seals between the epithelial cells.
32
What types of proteins make up tight junctions?
Transmembrane proteins and cytoplasmic proteins
33
What are the three major transmembrane proteins in tight junctions?
Occludin, claudins, and JAM (junctional adhesion molecules)
34
what are epithelial cells
Epithelial cells are specialized cells that form the lining or covering of body surfaces, both inside and outside the body
35
Properties of epithelial cells:
● Cellular, avascular cells that line membranous structures
● Polarized
● Highly interconnected via cell-cell junctions
● Contain specialized structures
36
Where are epithelia cells found?
● Linings of the gut
● Glands (sweat, salivary, and mammary glands)
● Kidney tubules
● Respiratory tract (Bronchi)
37
What do epithelial cells do?
● Protection
● Barrier
● Absorption
● Secretion
38
Epithelial Cell types: Simple squamous
* location?
* function?
Location: Air sacs of lungs, heart lining, blood/lymphatic vessels
Function: allows materials to pass through by diffusion and filtration and secretes lubricating substance
39
Epithelial Cell types: Simple Cuboidal
* location?
* function?
Location: In ducts, secretory portion of small glands, kidney tubule
Function: secretes and absorbs
39
Epithelial Cell types: Simple columnar epithelium
* location?
* function?
Location:
* Ciliated tissues are in bronchi, uterine tubes/uterus
* Smooth tissues are in the digestive tract and bladder
FUnction: absorbs and secretes mucous and enzymes
40
Epithelial Cell types: Pseudostratified columnar epithelium
* location?
* function?
Location: Ciliated tissue lines the trachea and upper respiratory tract
Function: Secretion of mucus (the cilli move mucus)
41
Epithelial Cell types: Stratified squamous epithelium
* location?
* function?
Location: lines the esophagus, mouth, vagina
Function: protects against abrasion
42
How does diffusion work?
Substances flow from high concentration to low concentration and stop when equilibrium is reached (the net movement will go to zero here)
43
What is osmosis and how does it work?
Water moves towards areas of high solute concentration, attempting to equalize the concentrations
flows from low solute concentration (more water) → to High solute concentration (less water)
44
What happens if a solute cant move/diffuse?
it will create an osmotic gradient.
Water will move toward the side with more solute to balance concentration (osmosis). This can cause water to build up and increase pressure on that side.
This builds up hydrostatic pressure which can help move solutes.
45
What is the set up here? What will happen?
the membrane separated two sides with unequal amounts of a solute that CAN cross the membrane. There's more solute on side 2 than side 1. both have h2o in it.
46
What will happen here?
What happen:
* H2o will go from side 1 --> 2 (down conc grading)
* Solute go from side 2 --> side 3 (down its conc gradient)
now the concentrations of water and solute are equal on both sides
47
What happens to a penetrating solute when it’s unequal on both sides of a membrane?
It moves down its concentration gradient until both sides are equal.
48
What happens at dynamic equilibrium?
Solute and water continue to move, but there’s no net movement.
49
Do penetrating solutes affect osmotic balance between ICF and ECF?
No, because they can cross the membrane and don’t create lasting differences in water movement.
50
Why does water move here?
When you have more solute on one side, that side has less water in comparison — it's a more concentrated solution and water will response to that to dilute it and even out the concentration.
* leads to hydrostatic pressure
51
What is the set up of this?
This is showing the movement of water when a membrane seprates unequal solutions of a NONPENETRATING solute
so the solute is stuck on one side
52
What will happen with this set up?
Because there is unequal solute, there will be different osmotic pressure. Water will move by osmosis (water will move to the side with lower solute to the side with higher solute to create balance. (also creates hydrostatic pressure)
side with more solute = higher pressure
side with less solute = lower pressure
53
What are the 3 main classes of membrane transport?
* Unassisted membrane transport (passive diffusion)
* Assisted membrane transport (channels/carriers)
*Active transport
54
What is unassisted membrane transport?
Molecules pass directly through the membrane without help, moving down their concentration gradient (high → low). No energy needed.
55
What are examples of unassisted transport?
Oxygen (O₂)
Carbon dioxide (CO₂)
Small lipophilic molecules
56
What is assisted membrane transport?
Molecules move down their gradient, but need help from a channel or carrier protein. Still passive (no energy used).
57
What are examples of assisted membrane transport?
Na⁺, K⁺ (ions) through ion channels
Glucose via GLUT transporters
58
What is active transport?
Molecules are moved against their gradient (low → high) using energy (ATP) and a protein pump or carrier
59
What are examples of active transport?
Na⁺/K⁺ pump
Proton (H⁺) pumps in the stomach
60
What is carrier-mediated transport?
Transport of molecules using carrier proteins. It is saturable and shows a maximum rate of transport (Tm).
61
what does saturable mean
Saturable means there’s a limit to how much something can happen because the "helpers" (like carrier proteins) can get fully busy — or “full.”
62
What is saturation in carrier-mediated transport?
When all carrier binding sites are occupied and no additional molecules can be transported faster — transport rate levels off.
63
What is simple diffusion?
* saturable?
Passive movement of molecules across the membrane without carriers.
Not saturable; rate increases continuously with concentration.
64
What is the Transport Maximum (Tm)?
The highest rate at which carriers can transport a substance. Reached when all carriers are fully saturated.
65
What types of transport are assisted by proteins?
* Simple diffusion (through channels)
* Facilitated diffusion
* Secondary active transport
* Primary active transport
66
Which assisted transport types move molecules down their concentration gradient?
* Simple diffusion
* Facilitated diffusion
* Secondary active transport (uses energy indirectly)
67
Which assisted transport type moves molecules against their concentration gradient and uses direct energy?
primary active transport
* it uses ATP to transport solutes (such as Na/K pump)
68
What does it mean that protein-mediated transport is specific?
Transport proteins only bind and transport specific substances, like a key fits a lock.
69
What is saturation in protein-mediated transport?
When all transport proteins are occupied, the transport rate reaches its maximum and cannot increase further.
70
When all transport proteins are occupied, the transport rate reaches its maximum and cannot increase further.
Similar compounds compete for the same protein binding site, reducing transport efficiency.
71
what is facilitated diffusion
Passive movement of molecules down electrochemical gradient with a channel
72
What is secondary active transport (aka coupled transport)
ex?
Coupled transport uses the gradient of one molecule (usually sodium, Na⁺) to help move another molecule against its concentration gradient (from low to high concentration) across the membrane - no ATP used but it relies on the energy from the other molecule
ex: SGLT transporter
73
What’s the main difference between simple diffusion and carrier-mediated transport?
Simple diffusion: Molecules move directly through the membrane down their concentration gradient without help, no saturation.
Carrier-mediated transport: Molecules use specific carrier proteins to move (down or against gradient), can saturate when all carriers are full.
74
How does facilitated diffusion work for glucose?
Facilitated diffusion moves molecules like glucose through carrier proteins to transport them across the membrane down their concentration gradient.
Insulin increases glucose transport by activating these carriers, so in diabetes (low insulin), glucose transport decreases.
75
What is primary active transport?
Protein moves substance against concentration gradient using metabolic energy
* such as Na/K pump
76
What is symport (coupled transport type)
ex:
Molecules move in the same direction across the membrane.
ex: Sodium-glucose transport (SGLT).
77
What is SGLT
Sodium-glucose transport (SGLT)
Sodium moves down its gradient (from high concentration outside the cell to low concentration inside) and, in doing so, helps glucose move into the cell against its gradient.
sodium being outside the cell creates a high conc gradient. this gradient moves glucose into the cell (sodium goes into the cell as well)
78
What is anti port (coupled transport type)
ex:
Molecules move in opposite directions.
Example: Sodium-potassium pump (Na⁺/K⁺ pump)
79
What is the Sodium-potassium pump (Na⁺/K⁺ pump)
Sodium is pumped out of the cell while potassium is pumped into the cell using the energy from sodium's gradient.
80
What does the SGLT create inside the cell?
accumulate a positive charge inside the cell as sodium brings positive ions in.
81
Where does glucose absorption occur in the intestine?
In the intestinal epithelial cells lining the small intestine.
82
How does glucose enter intestinal cells from the gut lumen?
Via the Sodium-Glucose Linked Transporter (SGLT)
- this is a secondary active transport
83
How does glucose exit intestinal cells into the bloodstream?
Through facilitated diffusion using GLUT transporters at the basolateral membrane.
84
How does the presence of a competitive substance change the net flux vs. concentration gradient graph?
It shifts the curve downward, indicating a lower rate of transport at the same concentration gradient.
85
Where is the SGLT transporter fund and what is its purpose?
Where found: Mainly in the kidneys and small intestine
Purpose: Reabsorb glucose from filtrate (urine in kidneys) or absorb from food (in intestines) and put back into blood
86
osmolarity vs osmolality
* osmolarity: number of particles of solute per liter of solution - depends on the volume of the solution.
* osmolality: number of particles of solute per kilogram of solvent - depends on the mass of the solvent.
87
What is Serum glucose
the amount of glucose (sugar) present in the liquid part of your blood (serum) at any given time.
88
Why does serum osmolality decrease during treatment of hyperglycemia with insulin and fluids?
Because glucose (a major osmole) is lowered in the blood, reducing the total solute concentration in plasma.
89
What are the key features of Hyperosmolar Hyperglycemic State (HHS) and what is it?
it is a diabetes complication
Extremely high blood glucose, high serum osmolality, minimal/no ketones, no significant acidosis, severe dehydration.
90
What causes dehydration in HHS?
Osmotic diuresis (body lose lots of water via peeing) from glucose in the urine pulls out large amounts of water and electrolytes.
91
Why is osmolality important in treating HHS?
It reflects the severity of dehydration and guides how quickly to correct fluids to avoid cerebral edema.
92
What are the counter-regulatory hormones that raise blood glucose?
Glucagon, cortisol, epinephrine, growth hormone.
