Chapter 3: Cells - The Living Units Flashcards
What are Extracellular materials?
- Extracellular fluid
- Cellular secretions
- Extracellular matrix
What is Extracellular fluid?
Includes interstitial fluid, blood plasma, and cerebrospinal fluid.
ECF dissolves and transports substances. Includes amino acids, sugars, fatty acids, regulatory substances, and wastes.
What are cellular secretions?
Includes substances that aid in digestion and some act as lubricants
What is Extracellular matrix?
The most abundant Extracellular material. Most cells are in contact with jellylike substance made of proteins and polysaccharides. Cells secrete, and it is an organized mesh in the Extracellular space.
How much of the plasma membrane is made of cholesterol?
About 20% of the plasma membrane. It makes the membrane stiffer
What are the kinds of membrane proteins?
- Transport
- Receptors for signal transduction
- Enzymatic activity
- Cell-cell recognition
- Attachment to the cytoskeleton and ECM
- Cell to cell joining
What are the three kinds of cell junctions?
Tight junctions
Desmosomes
Gap Junctions
What do tight cell junctions do?
A series of integral protein molecules that fuse together like ZipLock. Forms an impermeable junction.
What do desmosomes cell junctions do?
These serve as anchoring junctions — mechanical couplings like rivets. On the inside of the cell, it has a button like thickening called plaques. Cells are held together by protein filaments (cadherins) and extracellularly by keratin filaments (part of the cytoskeleton) extend within the cell to hold it together.
What are gap junctions?
Allows selective communication between cells.
What is diffusion?
Movement of molecules or ions from an area of high concentration to an area of low concentration.
What is osmosis?
Movement of H2O from low concentration to high concentration.
What determines whether a given substance can cross the plasma membrane?
Lipid solubility and Size
However, small molecules can diffuse across if not lipid soluble, and other molecules can be transported by carrier molecules such as an ion channel or transport protein
What is tonicity?
This refers to the ability of a solution to change the shape (or plasma membrane tension) of cells by altering the cells’ internal water volume (tono = tension)
Isotonic means both solutions are the same and cells retain their normal shape
Hypertonic means the Extracellular solution has a higher concentration of non penetrating solutes, and thus the cell loses water
Hypotonic means the cytoplasm has lower concentration, and thus the cell takes on water and can burst
What is the difference between osmolarity and tonicity?
Osmolarity is based SOLELY on its total solute concentration. In contrast, Tonicity is based on how the solution affects cell volume, which depends on (1) solute concentration and (2) solute permeability of the plasma membrane.
What is the definition of primary active transport?
The process in which solutes are moved across cell membranes against electrochemical gradients using energy supplied directly by ATP using transport proteins called “pumps”
Define Secondary Active Transport
Driven by energy stored in concentration gradients of ions created by primary active transport pumps. Secondary active transport systems always move more than one substance at a time using a contransport proteins)
What are the two types of Vesicular Transport?
Endocytosis, exocytosis
Also transcytosis (moves substances into, across, and then out of the cell) common in endothelium cells
And Vesicular trafficking, which moves substances from one area in the cell to another.
What defines endocytosis? What are the three kinds?
Is the main way the cell brings in bulk solids, most macromolecules, and fluids (or transporting them across).
Phagocytosis
Pinocytosis
Receptor-mediated endocytosis
What is phagocytosis?
“Cell eating”
The cell engulfs relatively large or solid material (such as clump of bacteria, cell debris)
Uses pseudopods to envelop.
Forms “phagosome”
Most cases, fuses with a lysosome to be digested
Often white blood cells
What is Pinocytosis?
“Cell drinking”
Infolding plasma membrane surrounds a very small volume of Extracellular fluid containing dissolved molecules.
It is a routine function in most cells.
A non selective way of sampling Extracellular fluid.
Membrane absorbed is recycled back to the plasma membrane
What is receptor mediated endocytosis?
The main mechanism for specific endocytosis and transcytosis of most macromolecules. Endocytosis mediated by protein receptors.
What is exocytosis?
“Exporting” products or waste.
Vesicles have v-snares that bind to t-snares on the plasma membrane and release their contents.
What is the typical resting membrane potential?
-50 to -90 millivolts (mV)