Structures of Cells and Tissues; Cell Cycle and Cell Death Flashcards
LO: Describe the structure and primary function of the plasma membrane
Structure: Tri-laminar structure formed by a phospholipid bilayer with hydrophilic head facing outward and a hydrophobic core.
Primary function: Selective permeability
Secondary functions: Endocytosis, exocytosis, cell-cell communication
LO: 3 major components of the cytoskeleton
Microtubules, intermediate filaments, and microfilaments
LO: Explain the structures and functions of the major nuclear components
LO: Predict a cell’s relative activity based on the structural characteristics of nuclear components
LO: Describe the process of cell death (necrosis, apoptosis)
LO: Explain the cell cycle process (mitosis, meiosis)
What form of microscopy must be used to see the plasma membrane?
Electron microscopy
Name the biochemical components of the plasma membrane
Lipids: cholesterol, phospholipids, glycolipids
Proteins: Integral proteins, peripheral proteins
Carbohydrates: linked to proteins and lipids, form glycocalyx
Function of cholesterol in the plasma membrane
Regulating fluidity.
Higher concentration of cholesterol (like at the site of lipid rafts) reduces membrane fluidity
Describe the distribution of the four different phospholipids in the PM
Sphingomyelin and phosphatidyl-choline are near extracellular surface.
Phosphatidyl-ethanolamine and phosphatidyl-serine are more concentrated at the intracellular surface
Where are glycolipids located in the PM?
Only on the extracellular (outer leaflet) of the bilayer
Differentiate between integral proteins and peripheral proteins
Integral proteins traverse the membrane whereas peripheral proteins are anchored to either the intracellular or extracellular membrane
State the makeup, location, and functions of the glycocalyx
Connections of carbohydrates on the extracellular surface of the PM that aids in cell adhesion and recognition
Define Fluid Mosaic Model
This model explains the proteins clustered in the lipid bilayer of the PM, but are mobile within the bilayer
PM Membrane Asymmetry
Proteins tend to stay on respective sides of the PM
PM Membrane Mobility
Proteins can move around the membrane or may be held stable by intracellular structures
Types of endocytosis
Phagocytosis, pinocytosis, and receptor-mediated endocytosis
Clathrin
Slight depression in the PM where endocytosis is about to occur and then forms a cage-like scaffolding for the invagination
Membrane receptors are mainly ______proteins
Name the four main functions of membrane receptors
Glycoproteins
Functions: control PM permeability, regulate entry of molecules into cells, bind ECM molecules to cytoskeleton via integrins, act as transducers to translate extracellular events into an intracellular response via second messenger systems
The three types of membrane receptors:
Channel-linked, enzymatic, and G protein-coupled receptors (GPCRs)
Common type of enzyme that is present in enzymatic receptors in PM
How is this type of receptor activated and what does it do?
Protein kinases
Activation upon ligand binding. Catalytic activity is induced in associated peripheral proteins
Activated GPCRs trigger a ______ involving a second messenger (and many more after that).
Name 3 common second messengers
Signaling cascade
cAMP, Ca2+, and inositol phospholipid-signaling pathway
Describe the molecular and systemic implications or familial hypercholesterolemia.
What causes this condition?
Cells have a decreased ability to take in LDL from the blood stream. Leads to build up of cholesterol in the blood stream and accelerated development of atherosclerosis
Cause: inherited genetic defect disabling synthesis of LDL receptors or synthesis of functional LDL receptors
What do Venoms do to the PM?
Inactivation of acetylcholine receptors of skeletal muscle sarcolemma at NMJ (neuromuscular junction)
How do autoimmune diseases affect the PM?
In the disease state, autoantibodies are produced that specifically bind to and activate certain membrane receptors on the PM
Effect of cholera toxin on the PM and its larger scale consequences
The exotoxin alters G proteins to the point that it is unable to hydrolyze its GTP molecule.
In effect, cAMP builds up in the intestinal cells and causes excessive loss of water and electrolytes as diarrhea
Effect of the pertussis toxin on the PM and its larger scale consequences
Where does the toxin attach?
Toxin inserts ADP-ribose into the alpha-subunits of trimeric G proteins –> inactivates GPCRs
In effect, irritation of mucosa of the bronchial passages, causing whooping cough
Toxin attaches in the upper respiratory system
What are the two pathways of protein synthesis in the cell?
- Nucleus –> ribosomes in rough ER –> Golgi complex –> vesicle packaging of proteins
- Nucleus –> free ribosomes –> cytoplasmic proteins
Describe the structure of the mitochondria from inside to outside
Intercristae space/matrix: enclosed by inner mem, contains Ca2+
Cristae: folds in inner membrane
Intermembrane space
Outer membrane
Functions of the mitochondria
Pyruvate oxidation: pyruvate –> acetyl CoA
Citric acid cycle: oxidizes acetyl CoA
Electron transport chain & oxidative phosphorylation: produces ATP (more than 100/second in each protein complex!)
Chemiosmotic process involved in ATP production
Characteristic of oxidative phosphorylation in forming ATP - electrochemical gradient across the inner membrane facilitates activation of ATP-synthase
When and how does the mitochondria induce apoptosis?
In response to cell stress, mitochondria release cytochrome c from intermembrane space into the cytoplasm.
Cytochrome c activates proteases that degrade all cellular components
Name an effective stain for displaying ribosomes
Hemaotoxylin (and other basic dyes)
Describe structure of the rough ER
Comprised of tubular system of membranes + ribosomes attached; continuous with unit membrane of nucleus
Describe the functions of the rough ER (3 broad ones)
- Synthesis and modification of proteins
- Isolation of synthesized proteins from cytosol
- Packaging for transport to Golgi apparatus
Modifications of proteins that could take place in the rough ER
Glycosylation, sulfation, phosphorylation, cleavage, assembly of proteins
What is the Agranular ER?
A network of membranes within the cell.
AKA: smooth ER
Functions of the smooth ER (5)
- Detoxification
- Steroid hormone synthesis and cholesterol metabolism
- Regulation of Ca2+ concentration in the cell
- Glycogen breakdown
- Lipid and lipoprotein synthesis; phospholipid synthesis
Where are phospholipids synthesized?
Smooth ER
Describe the structure of the Golgi Apparatus
The Golgi app is made of stacked cisternae with vesicles budding off cisternae. Molecules coming in are received at the cis-face and molecules exiting do so through the trans-face
Name the 3 functions of the Golgi
- Receives proteins and lipids from rough ER
- Continuation of protein glycosylation, sulfation, phosphorylation, and proteolysis
- Packaging of proteins and dispatch to various destinations
Lysosomes (in general)
Spherical membrane-enclosed vesicles that function as sites of intracellular digestion
Primary lysosomes
Freshly made by the Golgi, unused
Secondary lysosomes
Activated upon fusing with vesicles containing phagocytic materials (phagosomes)
Residual bodies
Membrane-encased debris of lysosome activity; contain lipofuscin
Proteasomes
Constitutive pathway for degradation of cellular proteins
Describe the role of ubiquitin in proteasomes
Proteins are conjugated to ubiquitin by ubiquitin ligase, then poly-ubiquinated proteins are targeted for proteolysis by the proteasome
Peroxisomes - location, contents, and function
Buds off of ER
Contains oxidative enzymes (amino acid and hydroxyacid oxidases) catalase (to get rid of hydrogen peroxide)
Functions:
1. Production and breakdown of hydrogen peroxide
2. Lipid metabolism
3. Bile salt synthesis
4. Detoxification
What is the role of secretory granules?
They are small granules containing neurotransmitters, hormones, growth factors, and enzymes that are released into the external environment of cells
What are inclusions in the PM? Provide 3 examples
They are NOT organelles; they have little-no metabolic activity, but contain accumulated metabolites and other substances not enclosed by membrane. Ex: fat droplets, glycogen granules, pigment deposits
Name the four pigments deposits that are found in inclusions in the PM
Melanin, Hemosiderin, Lipofuscin, and Bilirubin
Function of the cytoskeleton
Structural support and cell/organ motility
Three main components of the cytoskeleton
Microtubules (alpha and beta tubulin), intermediate filaments (cell-specific), and microfilaments (actin)
Key features of Microtubules
Polymerization occurs at the leading edge.
Can be structurally cross-linked by microtubule-associated proteins
Can be randomly distributed in a cell or form specialized structures: centrioles, cilia and flagella, basal bodies, mitotic spindles
Functions/features and types of Intermediate Filaments
Smaller diameter that microtubes, provides structural support.
Types (vary by cell): cytokeratins, desmin, glial-fibrillary acidic proteins, lamins, peripherin, vimentin
Features and function of Microfilaments
Smallest diameter in cytoskeleton, involved in cell contraction, motility, movement of cytoplasmic components, microvilli contraction
