functional anatomy of cells Flashcards
4 major cell structures of eukaryotic cells
- Plasma membrane
- Cytoplasm
- Nucleus
organelles
cell membrane structure
Contain a variety of membranes:
1. PLASMA MEMBRANE: encloses the cell 2. ORGANELLE MEMBRANES: sacs and canals made of the same material as the plasma membrane that enclose organelles such as the ER and Golgi 3. Membrane structure-lipid bilayer of phospholipid molecules
how do membranes function in physiology
- Control transport in and out of cell-urinary system ex: wtaer channels
- Allow selective receptivity and signaling via transmembrane receptors-endocrine
- Surface glycoproteins-immune system
- Anchor for cytoskeleton or ECM. Imp for movement, tissue structure
- Cell signalling provides sites for the binding and catalysis of enzymes
Provide a passageway across the membrane for certain molecules, such as in gap junctions. Cell-cell communication-intrinsic control
surface glycoprotein and immune surveillance
- Self markers (MHC) - molecules on the surface of human cells that are unique to an individual, thus identifying the cell as self to immune system
- SELF-TOLERANCE: the ability of our immune system to attack abnormal or foreign cells bt spare our own normal cells
NON-SELF MARKERS: molecules on the surface of foreign or abnormal cells or particules act as flags to the immune system as non-self
- SELF-TOLERANCE: the ability of our immune system to attack abnormal or foreign cells bt spare our own normal cells
endocrine system: structure + functions
Structure: membrane receptor
Functions: when bound by a ligand triggers an intracellular signaling cascade that will alter intracellular activities ex: FSH hormone receptor
functions of proteins in cell membrane in cell adhesion
1.
STRUCTURE: integral (span entire membrane) membrane proteins
FUNCTIONS: binds other integral membrane proteins to form cell-cell connections
2.
STRUCTURE: integral membrane proteins
FUNCTIONS: binds ECM to give structure to tissues
integrins: an example of structural adhesin protein
- Function in cell adhesion
- Join cell-to-cell or cell to ECM
- Heterodimer made of an alpha or Beta subunits
- Integral proteins
- Involved in:
1. Wound healing
2. Angiogenesis
3. Development
4. Embryo attachment
Cancer invasion
cytoplasm
Gel-like internal substance of cells that includes many organelles suspended in watery intracellular fluid called cytosol
2 major groups of organelles
- MEMBRANOUS ORGANELLES are specialized sacos or canal made of cell membrane
Ex: golgi, ER, plasma membrane, lysosomes, proteosomes- NONMEMBRANOUS ORGANELLES are made of microscopic filaments or other nonmembranous materials
Ex: cytoskeleton, ribosomes, cilia and flagella, nucleolus (important for formation of ribosomes)
- NONMEMBRANOUS ORGANELLES are made of microscopic filaments or other nonmembranous materials
endoplasmic reticulum
- STRUCTURE: made of canals with MEMBRANOUS WALLS present throughout the cytoplasm; extend from the nucleus to the plasma membrane
- FUNCTIONS: think of the ER like a river circulating through the cell for protein transport to get from the cucleus to the cytoplasm to the cell surface for release. Protein move throught the canals
2 types of endoplasmic reticulum
- Rough endoplasmic reitculum:
- RIBOSOMES found on the outer surface of the membranous walls
- Ribosomes synthesize proteins
- Function in proteins synthesis and intracellular transportation
- Transports protein to Golgi
- Smooth endoplasmic reticulum
- DOES NOT HAVE RIBOSOMES on the membranous wall
- Synthesizes certain lipids and carbohydrates
- Makes membrane for use throughout the cell
- Removes and stores CA+ from cells interior. ** important for muscle contraction, and in hormone production
route of protein transport
- Ribosomes on ER synthesize proteins and these ones move through the canals of the ER and are folded and assemble into macromolecular groups
- Proteins destined for cell export or cell membrane (RER)
The proteins then go to the golgi complex to be modified
- Proteins destined for cell export or cell membrane (RER)
5 steps: 1. Proteins made on ribosomes on ER 2. Travel through ER 3. Leave ER in vesicle fuse with Golgi 4. Modified in golgi Vesicle fuses with plasma membrane for release of protein outside the cell
ribosomes-protein factories
- Ribosomes (non-membranous)
- Many are attached to the rough endoplasmic reticulum and many lie free, scattered through the cytoplasm
- Each ribosome is a NON-MEMBRANOUS structure made of 2 pieces, a large subunit and a small subunit; each one is composed of rRNA (ribosomal RNA)
- Free ribosomes make proteins for the cells domestic use
- Those attached to the ER make protein for export
Working ribosomes form groups known as polyribosomes
Golgi
Gogli apparatus:
STRUCTURE: MEMBRANOUS organell consisting of cisternae stacked on one another and located near the nucleus
FUNCTIONS: processes and packages PROTEIN MOLECULES from th endoplasmic reticulum. Proteins are modified by enzymes residing in the golgi. For ex: attachment of a carbohydrate group
- Processed proteins leave the final cisternae in a vesicle; contents may then be secreted to outside the cell
lysosomes
STRUCTURE: made of microscopic MEMBRANOUS SACS that have pinched off from gogli apparatus
FUNCTIONS:
1. cell digestive/recycling system performed by enzymes
2. Break down proteins, food molecules, foreign particules (neutrophils) suc as bacteria, old organelles
3. Amino acids are recycled
** TAY-SACHS DISEASE caused by a failure to produce an enzyme needed to break down LIPIDS-GANGLIOSIDES (FA derivatoves found in all cell membranes)
proteosome-protein destroying unit
- Break down protein molecules one at a time by tagging each one with a chain of UBIQUITIN MOLECULES and unfolding it as it enters the proteosome, then breaking apart peptide bonds
- Short peptide chains exit the other end of the proteosome
In PARKINSON idsease the proteosome system fails and improperly folded proteins kill nerve cells in the brain that regulate muscle tension
- Short peptide chains exit the other end of the proteosome
mitochondria
STRUCTURE: composed of inner and outer membranes separated by fluid
- ENZYMES attached to both membranes - FUNCTION: the power plants of cells mitochondrial enzymes catalyze series of oxidation reactions that provide about 95% of cell's energy supply - Each mitochondrion has a single circular DNA molecule, allowing it to produce its own enzymes and replicate copies of itself - Only inherited from mother, involved in PARKINSON, ALZHEIMER AND DIABETES inheritance
nucleus structure
STRUCTURE:
- Consists of nuclear envelope (composed of 2 membranes each with the same molecular structure as plasma membrane) surrunding nucleoplasm - Nuclear envelope has holes called nuclear pores to allow proteins such as transcription factors in and out of the nucleus - Majority of normal cells have a single nucleus. Multinucleated cells are often associated with cancerous cells - Normally multinucleated cells include skeletal
DNA in nucleus
Contains DNA (heredity molecules), which appear as the following:
1. HETEROCHROMATIN- silent genes, tightly compacted 2. EUCHROMATIN- active site of gene expression/transcription * * gene trasncription determines phenotype!
cytoskeleton
STRUCTURE: internal supporting framework made up of rigid, rodlike pieces
FUNCTIONS: provide support
1. Allows movement of cells and of proteins and organelles within the cell
The cytoskeleton at mitosis and meiosis serves critical functions in chromatin movement and mechanisms
microfilaments
- Smallest cell fibers are microfilaments
- Made of thin, twisted strands of protein molecules that lie parallel to the long axis of the cell
- Microfilaments can slide past each other, causing shortening of the cell-muscle contraction
intermediate filaments and microtubule
- INTERMEDIATE FILAMENTS: are twisted protein strands slightly thicker than microfilaments; they form much of the supporting framework in many types of cells
Ex: protective outer layer of cells- MICROTUBULES are tiny, hollow tubes that are the thickest of the cell fibers; they are made of protein subunits arranged in a spiral fashion; their function is to MOVE THINGS AROUND IN THE CELL
centrosome
- An area of the cytoplasm near the nucleus that coordinates the BUILDING AND BREAKING OF MICROTUBULES in the cell
Plays an important role during cell division
rat model
- Dr. Douglas Kerr- John Hopkins, rat model to show that stem cell therapy is a viable treatment for restoration of function to damaged nerved cells
- ESC were injected into rat spinal cord fluid who model nerve disease
- Stem cells did not regrow but restored the environment to prevent further damage
- Testing what stem cell source is best, some go on to make neurons and greater rates so may have a greater rate of replacement then other stem cell sources
functions of protein in cells ex: urinary system
STRUCTURE: protein channel
FUNCTION: controlled transport of water soluble molecules.
Ex: movement of sodium and potassium
- Specificity is given by recognition of the shape of the molecule. Can open or close-gated channels
Ex: important for regulating water
adjusting the urine in dehydration
- The initial response to cellular dehydration is release of ADH (by hypotalamus)
- ADH acts on the distal tubule of the kidney to increase water permeability by inserting aquaporin channels into cell membranes
- Water moves out of the distal convoluted tubule of the kidney by osmosis trhough these channels - decreasing osmolarity
- Overall effect is an increased water reabsorption by the kidney and a decrease in urine flow
1 example of cell adhesion molecule
Uterine cross sections at embryo implantation (integrin alpha 6)
proteins (histone) in a nucleosome
2 H2B 2 H4 H2AC H2A 2 H3
mechanism of action
- The myosin heads bend with a strong force when they bind the actin filaments
- This pulls the thin filaments past them
- Each head then release and this pulls again
- This pulling by the myosin heads and the sliding of the actin is the essential movement of the muscle contraction
- known as the Sliding filament model
cytoskeleton cell extensions= microvilli and cilia
- Cytoskeleton forms projections that extend the plasma membrane outward to form tiny, fingerlike processes
- Microvilli formed from microfilaments
- Cilia and flagella formed by microtubules
There are three types of these processes; each has a specific fonction:
1. MICROVILLI: found in epithelial cells that line the intestines and other areas where absorption is important; they help to increase the surface area
CILIA AND FLAGELLA: cell processes that have cylinders made of microtubules at their core; cilia are shorter and more numerous than flagella; flagella are found only on human sperm cells
anchoring junctions: desmosomes
- Fibers on the outer surface of each desomosome interlock with each other (VELCRO); anchored internally by intermediate filaments of the cytoskeleton
- Spot desmosomes, connecting adjacent membranes, are like spot welds at various points
Belt desmosomes encircle the entire cell like a collar
- Spot desmosomes, connecting adjacent membranes, are like spot welds at various points
gap junctions
- Fibers on the outer surface of each desomosome interlock with each other (VELCRO); anchored internally by intermediate filaments of the cytoskeleton
- Spot desmosomes, connecting adjacent membranes, are like spot welds at various points
Belt desmosomes encircle the entire cell like a collar
- Spot desmosomes, connecting adjacent membranes, are like spot welds at various points
contractile cells
- Individual cardiac muscle cells are joined by INTERCALATED DISCS
- Within the intercalated disc there are 2 types of connections: desmosomes and gap junctions
- Gap junctions are areas of low electrical resistance and allow for electrical impusles to spread from one cardiac cell to the next
- Functional syncytium-cardiac cells joined by GJ, one is stimulated they all contract
- The atria and ventricles form separate functional syncytium, allows for coordinated contraction and complete empyting
tight junctions
- Occur in cells that are joined by collars of tightly fused material
- Molecules cant permeate the cracks og tight junctions
- Occur in the lining of the intestines and other parts of the body, where its importamt to control what gets through a sheet of cells
- Important in the intestinal epithelium so that enzymes cant reach underlying stroma layer
