MEMBRANE TRANSPORT & TISSUE STRUCTURE/FUNCTION Flashcards
Cell membrane
Surrounds the cell to separate internal contents with the extracellular environment and regulates passage of molecules through
Why must cell membrane be dynamic and constantly in flux
Because cells exclude some substances, take in others, and excrete others, all in controlled quantities which requires the membrane to be dynamic and constantly in flux
Singer & Nicolson 1972
Proposed the fluid mosaic model which sought to explain the microscopic observations and the functions of the cell membrane
Mosaic of components of the membrane (4)
Phospholipids, cholesterol, proteins, and carbohydrates
Phospholipid backbone
Primarily made up of a bilayer of phospholipids. The hydrophilic head of the phospholipids are in contact with the water-based intracellular and extracellular fluid while the hydrophobic fatty acid tails point towards each other at the interior of the membrane
Cholesterol in cell membrane
Contributes to the fluidity of the membrane
Amphipathic
Molecule that contains both a hydrophilic and hydrophobic region (eg. Soap)
Integral proteins
Proteins embedded in the plasma membrane and may span all of parts of the membrane to sere as channels, gates, or pumps to move materials into or out of cells
Peripheral proteins
Found on exterior or interior surfaces of the membrane, attached either to the integral proteins or phospholipid molecules. Stabilizes and gives shape to membrane
Carbohydrates
Found on the exterior surface of cells and are bound to either proteins as GLYCOPROTEINS or lipids as GLYCOLIPIDS
Glycoprotein
Protein that has a carbohydrate molecule attached which extends to the extracellular matrix
Glycocalyx
Fuzzy appearing coating around cell formed from glycoproteins and other carbohydrates that surrounds the other most cellular membrane of cells. Glycocalyx consist of 2-60 units that may be either straight or branches
Glycocalyx functions (4):
- Can have molecules that allow cell to bind to another cell
- Can contain receptors for hormones
- Can have enzymes to break down nutrients
- Gives identity of belonging in the person’s body. Knows the body’s own cells (reason for organ donor rejection)
Selective permeability
Ability to differentiate between different types of molecules, only allowing some molecules through while blocking others assisted by the hydrophobic and hydrophilic characteristics of the membrane
Things that can/cannot pass through selective permeable membrane (4):
- Lipid-soluble material can easily slip through the hydrophobic lipid core
- Molecules like CO2 and O2 have no charge and pass through easily
- Substances that are polar (water) cannot pass easily
- Ions or molecules cannot pass easily or at all through the hydrophobic core
Diffusion (4):
- Passive process requiring NO energy
- Movement from an area of high concentration to an area of low concentration until equilibrium is reached
- Can occur across the selectively permeable membrane of living cells if molecules can pass through the hydrophobic core
- In a system with more than one substance, each separate substance has its own concentration gradient
Simple diffusion
When molecules make their way across the cell membrane without any assistance
Factors affecting diffusion (4):
- Concentration gradient: Greater the difference in concentration, the more rapid the diffusion
- Mass of molecules that are diffusing: Larger molecules move more slowly because it is more difficult for them to move in substance when there are little to no space between molecules they are moving through
- Temperature: High temperature increases energy and the movement of molecules = increased rate of diffusion
- Solvent density: As the density of the solvent increases, the rate of diffusion decreases because the molecules have a difficult time getting through the denser solvent
Facilitated diffusion
Assists molecules that cannot pass through the cell membrane by simple diffusion (polar molecules, ions, large compounds) with the help of specific integral proteins called transmembrane integral proteins
Transmembrane integral protein
Specific integral proteins that span the membrane that assist this movement of facilitated diffusion to occur
Two types of transmembrane integral protein:
- Channel proteins
- Carrier proteins
- Both of these are examples of diffusion thus NO ENERGY NEEDED
Channel proteins
Selectively allows particular materials, like certain ions to pass in and out of cell
Carrier proteins
Interact with the substance and shuttle it across the membrane
Osmosis
Diffusion of water across a selectively permeable membrane; only water is transported and follows the concentration gradient of low concentration to high concentration
Why is osmosis even a thing
Because a selectively permeable membrane will limit the passage of solutes, but rarely limit the passage of water
Tonicity
Describes the amount of solute in a solution
Osmolarity
The measure of the total amount of solute dissolved in the solution
3 terms used to relate the osmolarity of a cell:
- Hypotonic
- Hypertonic
- Isotonic
Hypotonic solution
Has a lower concentration of solutes than the fluid inside the cell; net movement of water INTO cell via osmosis (eg. RBC swelling and bursting)
Hypertonic solution
Has a higher concentration of solutes than the fluid inside the cell; net movement of water OUT the cell via osmosis (eg. RBC shrivelling)
Isotonic solution
Has the same concentration of solutes as the fluid inside the cell; no net movement of water into or out of cell (eg. RBC no change)
Active transport
Mechanism that requires the use of the cell’s energy (ATP) when substances must move into a cell AGAINST its concentration gradient
2 classifications of active transport mechanisms:
- Movement of solute molecules across membrane using ATP
- Expulsion of substances out of cell by exocytosis
-Primary active transport
-Secondary active transport
- Directly uses a source of chemical energy (e.g., ATP) to move molecules across a membrane against their gradient
- Uses an electrochemical gradient – generated by active transport – as an energy source to move molecules against their gradient, and thus does not directly require a chemical source of energy such as ATP
Secondary active transport
Movement of a substance across the cell membrane using the energy invested in the active transport of a different substance (active transport powers the movement of another substance)
Endocytosis
Ingestion of large particles like bacteria and the uptake of fluids or macromolecules in small vesicles from outside the cell
Phagocytosis
“Cell eating” Cell engulfing large particles; important for removing pathogens and cell debris
Pinocytosis
“Cell drinking” Cells engulfs droplets of extracellular fluid along with dissolved small molecules
Receptor mediated endocytosis
Importing macromolecules from the extracellular fluid. The macromolecules bind with the specific receptors
Exocytosis
“Taking out the cell” Opposite of endocytosis, a process that expels materials from the cell into the extracellular fluid through fusion of secretory vesicles with the plasma membrane
Tissue (4):
- Group of cells found together in the body that share a common embryonic origin
- Share morphological features
- Arranged in an orderly pattern
-Different types of tissues have distinct shapes and structures that contribute to increased efficiency in carrying out specific functions in the body.
4 broad categories of tissues in human body:
- Epithelial tissue
- Connective tissue
- Nervous tissue
- Muscle tissue
Epithelial tissue
Refers to the sheets of cells that cover all body surfaces, lines internal cavities and hollow organs, and forms certain glands
Basal lamina
Mixture of glycoproteins and collagen that attaches to reticular lamina
Epithelial tissue general structure (6):
- Highly cellular; little or no extracellular materials
- Cells exhibit polarity; structural and functional differences between apical and basal cells
- Basal cells attach to basal lamina providing attachment site for epithelium separating from connective tissue
- Basal lamina attaches to reticular lamina made of reticular fibres (secreted by underlying connective tissue) forming basement membrane (barrier between epithelium and connective)
- Nearly completely avascular
- Capable of rapidly replacing damaged or dead cells
Epithelial tissue general function (3):
- Body’s first line of defense from physical, chemical, and biological wear and tear
- Control permeability of substances in body
- Many capable of secretion of mucous and other chemicals onto apical surface
Main shapes of epithelial tissue (3):
Squamous (flattened and thin), cuboidal (box shaped), or columnar (rectangular)
Simple epithelium
1 cell layer
Stratified epithelium
More than 1 layer of cells
Pseudostratified epithelium
Single layer of irregularly shaped cells that give the appearance of multiple layers
2 classes of arrangement of cell layers
Simple and stratified
Main 8 epithelial tissues
- Simple squamous epithelium
- Simple cuboidal epithelium
- Simple columnar epithelium
- Pseudostratified columnar epithelium
- Stratified squamous epithelium
- Stratified cuboidal epithelium
- Stratified columnar epithelium
- Transitional epithelium
- Simple squamous epithelium (4)
- Simple Cuboidal (2)
- Simple Columnar (5)
- Found in air sacs of lungs and the lining of heart, blood vessels and lymphatic vessels. Allows materials to pass through by diffusion and filtration and secretes lubricating substance
- Ducts/secretory areas of small glands and kidney tubules for secretion and absorption
- Ciliated tissues in bronchi, uterine tubes, uterus. Nonciliated in digestive tract, bladder to secrete and absorb mucus/enzymes
Pseudostratified columnar epithelium
Ciliated tissue lines the trachea and much of the upper respiratory tract. Allows secretion of mucus and the ciliated tissue moves mucus
- Stratified Squamous
- Stratified Cuboidal
- Stratified Columnar
- Lines the esophagus, mouth, and vagina and protects against abrasion
- Sweat glands, salvary glands, mammary glands to act as protective tissue
- Male urethra, ducts of glands to secrete and protect
Transitional epithelium
Lines the bladder, urethra, and the ureters and allows the urinary organs to expand and stretch
Connective tissue
Binds cell and organs of the body together and functions in the protection, support, and integration of all parts of the body
General structure of connective tissues (3):
- Dispersed in a matrix that usually includes a large amount of extracellular material produced by the connective tissue cells
- Matrix plays a major role in tissue’s functioning
- Composed of ground substance (mainly water), protein fibers, and cells
General function of connective tissues (5):
- Support and connect other tissues; MAIN FUNCTION
- Protein of delicate organs
- Defense against microorganisms
- Transport of fluid, nutrients, waste, and hormones
- Energy storage and insulation by fat
Connective tissue proper
A kind of connective tissue that is of two types loose and dense connective tissue
Connective tissue proper (3):
- Fibroblasts: Secretes three types of protein fibers; collagen, elastic, reticular
- Adipocytes: Stores lipids as droplets that fill most of the cytoplasm
- Mesenchymal cells: Multipotent adult stem cells that can differentiate into any type of connective tissue cell
Mast cell
Found in connective tissue proper that release histamine when irritated or damaged
Connective tissue proper (LOOSE)
- Found between many organs where it acts to absorb sock and bind tissues together. Provides support, cushioning, and flexibility
3 main types of connective tissue proper LOOSE
- Adipose tissue: Consists mostly of fat storage cells with very little extracellular fluid
- Areolar tissue: Little specialization and contains all the cell types and fibers found in connective tissue
- Reticular tissue: Mesh-like supportive framework for soft organs
Reticular fibroblast cells
Produces reticular fibers that form the network onto which other cells attach. Releases collagen fibers, elastic fibers and reticular fibres
Connective tissue proper (DENSE)
Contains more collagen fibers than loose connective tissues
2 connective tissue proper DENSE
- Dense regular connective tissue: Has fibers that are parallel to one another, enhancing tensile strength in the direction the fibers run
- Dense irregular connective tissue: Randomly orientated fibers giving enhanced overall strength
Supportive connective tissue
Tissue that provides structure and strength to the body and protects soft tissues with few cell types and densely packed fibers (eg. Cartilage and bones)
Supportive connective tissues (CARTILAGE) (4):
- Has distinct appearance due to polysaccharides the bind with the ground substance and is completely vascular, making it a slow healing tissue
- Chondrocytes: Cells that compose cartilage
- Lacunae: Hollow space in the matrix
- Perichondrium: Layer of dense irregular connective tissue that encapsulates the cartilage
3 main types of cartilage
- Hyaline cartilage
- Fibrocartilage
- Elastic cartilage
Hyaline cartilage
Most common type and contains short and dispersed collagen fibers in the matrix (found in rib cage, nose, and covers bones that meet to form moveable joints in body)
Fibrocartilage
Contains thick bundles of collagen fibers and dispersed throughout matrix = tough
Elastic cartilage
Contains elastic fibers as well as collagen and gives rigid support and elasticity found in external ear and epiglottis
Supportive connective tissues (BONES) (3):
- Hardest connective tissue providing protection to internal organs and support for body
- Matrix is rigid and contains mostly collagen fibers embedded in a mineralized ground substance of hydroxyapatite (calcium phosphate)
Types of bones (2):
- Cancellous bones
- Compact bones
Cancellous bones
Called spongy bone or trabecular bone and looks like a sponge under microscope. It contains many spaces between trabeculae and is found in the interior of some bones and the end of long bones
Compact bones
Solid and has greater structural strength and is the major component of bones
Fluid connective tissue
Tissue with various specialized cells circulating in a watery fluid (eg. Blood and lymph)
Fluid connective tissue (BLOOD & LYMPH):
- Blood and lymph have cells circulating in liquid matrix
- RBC, WBC, platelets and all derived from hematopoietic stem cells in red bone marrow
- Lymph contains only white blood cells and collects liquid from interstitial fluid and draining into blood vessels
RBC
Transport CO2 and O2
WBC
Defends against potentially harmful microorganisms or molecules
Platelets
Forms blood clotting
Muscle tissues
Responds to stimulation and contracts to provide movement
Muscle tissue structure:
- Muscle cells are excitable and when they respond to a stimulus, they shorten and generate a pulling force
- Some muscle movement is voluntary and others are involuntary
3 types of muscle tissues:
- Skeletal
- Smooth
- Cardiac
Skeletal muscle
Long cylindrical fiber, striated with many peripherally located nuclei attached to bones and found around entrance points of body. It is responsible for the voluntary movements in the body
Smooth muscle
Short spindle shaped fibers, no striation, with single nucleus found in walls of major organs and passageways. It is responsible for involuntary movement (move materials through digestive tract and ducts, and regulate blood flow in arteries)
Cardiac muscle
Short-branched fibers, striated with single central nucleus and found in heart walls. It is responsible for contractions to pump blood
Nervous tissue
Allows for propagation of electrochemical signals in the form of nerve impulses that communicate between different regions of body
2 main classes of cells that make up nervous tissue
- Contains neurons (cells) that propagate information as action potentials
- Contains neuroglia (cells) that play an essential role in supporting neurons
Neuron structure:
- Structure is suited to their role as conducting cells
- Cell body
- Dendrites
- Long axon
- Synapse
Cell body
Has most cytoplasm, organelles, nucleus
Dendrites
Branch off from cell body and appear as thin extensions
Axon
Extends from neuron body and can be wrapped in an insulating layer known as myelin sheath
Synapse
Gap between nerve cells, or between nerve cell and its target cell, across which the impulse is transmitted by chemical compounds known as neurotransmitters
