Cell, Membrane Function and Homeostasis Flashcards
It is the 💡basic structural and 💡functional units, the 💡smallest living parts of the body
CELLS
Eukaryotic cells are distinguished from prokaryotic cells by the __
Presence of a membrane-delimited nucleus
2 Compartments of the cell:
NUCLEUS
CYTOPLASM
It is an aqueous solution containing numerous organic molecules, ions, cytoskeletal elements, and a number of organelles.
CYTOPLASM
Functions of the plasma membrane:
Selective transport of molecules
Cell recognition
Cell communication
Tissue organization
Membrane-dependent enzymatic activity
Determination of cell shape
Cell shape and movement, intracellular transport
Cytoskeleton
Genome (22 autosomes and 2 sex chromosomes), DNA and RNA synthesis
Nucleus
ATP synthesis by oxidative phosphorylation, Ca2+ storage
Mitochondria
Synthesis of lipids, Ca2+ storage
Smooth endoplasmic reticulum
Translation of mRNA into cytosolic proteins
Free ribosomes
Translation of mRNA into membrane associated proteins or for secretion out of the cell
Rough endoplasmic reticulum
Intracellular degradation
Lysosome
Cellular uptake of 💡cholesterol, removal of receptors from the plasma membrane, uptake of small molecules and water into the cell, internalization of large particles (e.g., bacteria, cell debris)
Endosome
💡Modification, sorting, and packaging of proteins and lipids for delivery to other organelles within the cell or for secretion out of the cell
Golgi apparatus
Degradation of intracellular 💡proteins
Proteosome
💡Detoxification of substances
Peroxisome
The major lipids of the plasma membrane:
PHOSPHOLIPIDS
PHOSPHOGLYCERIDES
These are 💡amphipathic molecules that contain a charged (or polar) hydrophilic head and two (nonpolar) hydrophobic fatty acyl chains
PHOSPHOLIPIDS
It has the amino alcohol 💡sphingosine as its “backbone” instead of glycerol
Sphingomyelin
Common alcohols attached to the membrane phospholipids:
💡💡 C E S I G
Choline Ethanolamine Serine Inositol Glycerol
Primary Location in Membrane of the given Phospholipids:
*Phosphatidylcholine
*Sphingomyelin
Phospatidylethanolamine
Phosphatidylserine
Phosphatidylinositol
IN RESPECTIVE ORDER *Outer leaflet *Outer leaflet Inner leaflet Inner leaflet Inner leaflet
It is a phospholipid that plays an important role in 💡signal transduction, and its location in the inner leaflet of the membrane facilitates this signaling role
Phosphatidylinositol
It is found in 💡both leaflets and serves to 💡stabilize the membrane at normal body temperature (37°C)
CHOLESTEROL
It consist of 💡two fatty acyl chains linked to polar head groups that consist of 💡carbohydrates
Glycolipids
It plays an important role in 💡anchoring proteins to the outer leaflet of the membrane
Glycosylphosphatylinositol (GPI)
As temperature increases, the __ of the membrane increases.
fluidity
The presence of __ in the phospholipids and glycolipids also increases membrane fluidity.
Unsaturated fatty acyl chains
One important function of these is to 💡segregate signaling molecules.
💡Aggregated lipids found in some regions of the membrane and often have an association with specific proteins, which diffuse in the plane of the membrane as a discrete unit
LIPID RAFTS
Classification of membrane proteins:
💡💡
I
L
P
Integral
Lipid-anchored
Peripheral
These are 💡imbedded in the lipid bilayer, where hydrophobic amino acid residues are associated with the hydrophobic fatty acyl chains of the membrane lipids.
Integral membrane proteins (Transmembrane Proteins)
-
Peripheral proteins
The normal function of cells requires the continuous movement of (1)__ and (2)__ into and out of the cell.
(1) WATER
(2) SOLUTES
4 General Groups of Membrane Transporters
💡💡 W I S A
Water channels Ion channels Solute carriers Adenosine triphosphate (ATP)–dependent transporters.
These are a membrane transporter which are the main routes for 💡water movement into and out of the cell
Water channels, or Aquaporins (AQPs)
These are a membrane transporter found in all cells, and are especially important for the function of 💡excitable cells
Ion channels
Classification of Ion Channels:
💡💡
S
C
G
Selectivity
Conductance
Mechanism of channel gating
It is defined as the nature of the ions that pass through the channel.
Selectivity
It refers to the 💡number of ions that pass through the channel and is typically expressed in picosiemens (pS)
Channel conductance
Factors that can control the Gating:
💡💡 M E I M
Membrane voltage
Extracellular agonists or antagonists
Intracellular messengers
Mechanical stretch of the plasma membrane
It is a solute carrier that transports a 💡single molecule across the membrane
Uniporters (or Facilitated Transporters)
Is is a solute carrier that couples the movement of 💡two or more molecules/ions across the membrane
The molecules/ions are transported in the 💡same direction
Symporters (or Cotransporters)
It couples the movement of 💡two or more molecules/ions across the membrane; in this case, however, the molecules/ions are transported in 💡opposite directions
Antiporters (or Exchange Transporters)
These are a membrane transporter that use the energy in 💡ATP to drive the movement of molecules/ ions across the membrane.
ATP-dependent transporters
Two groups of ATPdependent transporters:
ATPase ion transporters
ATP-binding cassette (ABC) transporters
The ATPase ion transporters are subdivided into:
💡💡
P
V
P-type ATPases
V-type ATPases (Vacuolar H+-ATPases)
Its is 💡phosphorylated during the transport cycle.
P-type ATPase
It is an important example of a P-type ATPase.
It is present in all cells and plays a critical role in establishing cellular ion and electrical gradients, as well as maintaining cell volume
Na+,K+-ATPase
It is found in the 💡membranes of several intracellular organelles (e.g., endosomes, lysosomes)
Plays an important role in 💡urinary acidification
V-type ATPases (Vacuolar H+-ATPases)
The process whereby a piece of the plasma membrane pinches off and is internalized into the cell interior
Endocytosis
The process whereby vesicles inside the cell fuse with the plasma membrane
Exocytosis
The transport of substances inside the vesicles across the Epithelia
Transcytosis
An autosomal recessive disease characterized by chronic lung infections, pancreatic insufficiency, and infertility in boys and men.
It is a result of mutations in a gene on 💡chromosome 7 that codes for an ABC transporter
Caused by defective epithelial transport.
Cystic fibrosis
-
Cystic Fibrosis Transmembrane Conductance Regulator (CFTR)
Three Mechanisms of Endocytosis;
PINOCYTOSIS
PHAGOCYTOSIS
RECEPTOR MEDIATED ENDOCYTOSIS
Uptake of 💡small molecules and 💡water into the cell
Is a prominent feature of the endothelial cells that line capillaries and is responsible for a portion of the fluid exchange that occurs across these vessels.
PINOCYTOSIS
It allows for the cellular internalization of 💡large particles
PHAGOCYTOSIS
Mechanisms of Receptor Mediated Endocytosis
💡💡 Ligand + Receptor Clathrin coated pits Dynamin Recycle Uncoating
Receptors on the surface of the cell bind the ligand. A clathrin-coated pit is formed with adaptin linking the receptor molecules to clathrin. Dynamin, a guanosine triphosphatase (GTPase), assists in separation of the endocytic vesicle from the membrane. Once inside the cell, the clathrin and adaptin molecules dissociate and are recycled. The uncoated vesicle is then ready to fuse with other organelles in the cell (e.g., lysosomes).
It is the process by which molecules move spontaneously from an area of high concentration to one of low concentration.
DIFFUSION
Diffusion is a random process driven by the __.
Thermal motion of the molecules
It quantifies the rate at which a molecule diffuses from point A to point B:
Fick’s first law of diffusion
The rate of diffusion will be __ for small molecules than for large molecules.
Faster
Diffusion rates are __ at 💡elevated temperatures, in the presence of 💡large concentration gradients, and when diffusion occurs in a 💡low-viscosity medium.
High
It is used to 💡quantitate the driving force acting on a molecule to cause it to move across a membrane
Electrochemical Gradient (also called the Electrochemical Potential Difference)
When the net movement of a molecule across a membrane occurs in the 💡direction predicted by the electrochemical gradient, that movement is termed?
PASSIVE TRANSPORT
Other term for passive transport?
“Downhill Transport” or “Transport with the Electrochemical Gradient.”
The net movement of a molecule across the membrane is 💡opposite to that predicted by the electrochemical gradient, that movement is termed __, a process that requires the input of 💡💡energy
ACTIVE TRANSORT
Other term for Active Transport?
“Uphill Transport” or “Transport against the Electrochemical Gradient.”
The 💡movement of water across cell membranes occurs by the process of?
OSMOSIS
In osmosis, the movement of water is (1)__, with the driving force for this movement being the (2)__ across the cell membrane.
(1) Passive
(2) Osmotic Pressure Difference
It is determined by the 💡number of solute molecules dissolved in the solution.
OSMOTIC PRESSURE
Osmotic pressure is not dependent on such factors as the:
💡💡
S
C
Size of the molecules Mass
Chemical nature
Osmotic pressure (π), measured in (1)__, is calculated by (2)__
💡💡
A
V
(1) Atmospheres (atm)
(2) van’t Hoff’s law
Refers to the osmotic pressure generated by the dissolved solute molecules in 💡1 L of solvent
OSMOLARITY
The number of molecules dissolved in 💡1 kg of solvent.
OSMOLALITY
Osmolality Fomula
2(Na) + BUN/3 + Glucose/18
Measurements of 💡osmolarity are __ because the volume of the solvent varies with temperature
Temperature Dependent
💡Osmolality, which is based on the mass of the solvent, is __.
Temperature Independent
Solutions that 💡do not change the volume of a cell are said to be?
ISOTONIC
Solution causes a cell to 💡swell
HYPOTONIC
Solution causes a cell to 💡shrink
HYPERTONIC
To exert an osmotic pressure across a membrane, a molecule __ the membrane.
Must not cross
It can generate an osmotic pressure across the membrane.
EFFECTIVE OSMOLE
It cannot generate an osmotic pressure across the membrane.
INEFFECTIVE OSMOLE
It is the osmotic pressure 💡generated by large molecules (especially proteins) in solution.
ONCOTIC PRESSURE
It is defined as the weight of a volume of solution divided by the weight of an equal volume of distilled water.
It measures the 💡total concentration of all molecules in a solution.
SPECIFIC GRAVITY
