lecture 3 Flashcards
General Cell Structure
what is the basic unit of living organism
the cell
what is the function of the plasma membrane?
more than just a barrier, it has functions like signal transduction, ETC, with lots of organization
what organelle is exclusive to animal cells?
lysosomes
what is the composition of a red blood cell?
no nucleus, no ER, large sacs of hemoglobin, and enzymes to convert carbon dioxide into bicarbonate
what is the function of the plasma membrane?
separate two aqueous compartments (intercellular organelles from cytoplasm and cytoplasm from outside environment. Also regulates the transport of molecules from one compartment to another.
what is the function of the lysosomes?
contain degradative enzymes that recycle material the cell no longer requires; these are intracellular organelles of digestion, surrounded by a single membrane, they contain digestive hydrolase enzymes, pH maintained via vesicular ATPases, participate in autophagy and in receptor mediated endocytosis
what is the function of the mitochondria?
the cells power plant, and generate ATP through the oxidation of fuel sources, and reduction of oxygen to water. It has two outer membranes, has a circular genome 10-20 genes.
what are peroxisomes?
cellular components devoted to highly reactive oxidative reactions (O2/H2O2); Contains enzymes such as catalase, D-amino acid oxidase, and uric acid oxidase; Primarily function to rid the cell of toxic substances, particularly hydrogen peroxide (H2O2); Involved in catabolism of very long chain fatty acids through beta-oxidation; Biosynthesis of plasmalogens (ether phospholipids) critical for the normal function of the brain and lungs
what is the nucleus?
the site of DNA storage and replication, RNA synthesis, and ribosome assembly
what is the endoplasmic reticulum?
responsible for protein synthesis, post-translational modification, metabolic processes
what is the golgi complex?
processes proteins, sort and send proteins to various parts of the cells; also used for post translational modifications -include complex branched chain oligosaccharide addition, sulfation, and phosphorylation
cytoskeleton?
provides cellular structure and transports materials within the cell; consists of microtubules (movement of vesicles and organelles), thin filaments that form a network, and intermediate filaments used for structural support
what is so interesting about lysosomes?
they have a pH of about 5.5 used for degradation for unwanted cellular material
what is the plasma membrane comprised of?
a bilayer of phospholipids (phosphatidylcholine (mostly outer leaflet), phosphatidylethanolamine (mostly inner leaflet), phosphatidylserine and phosphytidyinositol (mostly inner leaflet), sphingomyelin (mostly outer leaflet), which consists of two fatty acids (hydrophobic) and one phosphate group (hydrophilic); also proteins can be found embedded and peripherally (also glycoproteins). Its continuous and sealed and because there is no uniform structure it is viewed as a fluid mosaic model
what are the principal phospholipids? how would you classify them as a group?
phosphatidylcholine (lecithin)
phosphotidylethanolamine
phosphotidylserine
sphingolipid: sphingomyelin; glycerol lipids - glycerol backbone and esterified with two long fatty acid chains and a phosphate head group (hydrophilic)
why are the components of the bilayer important?
maintaining viscosity of the membrane, sort of like olive oil
why is phosphotidylethanolamine important?
it dictates the curvature of the membrane because of its natural cone like shape; we more of these fats on the interior than exterior to provide shape for the cell
what is responsible for maintaining membrane fluidity?
cholesterol, also works with cis unsaturated fatty acids in the membrane
what are the types of proteins found in the plasma membrane?
intergral proteins, peripheral proteins, lipid anchored proteins
integral proteins?
these contain transmembrane domains and function as channels or transporters for movement of compounds across the membrane; important for forming channels, and dictating what goes in and out of cell
peripheral proteins?
proteins bound to polar head groups of lipids or integral proteins via weak electrostatic interactions, i.e.- spectrum bound to actin
what are lipid anchored proteins?
proteins bound to inner or outer surface or the membrane
what is the function of transmembrane proteins?
transporters, dictating what solutes go into and out of cell
what is the function of membrane associated proteins?
anchors used for things like signal transduction
what is the function of lipid linked proteins?
receptors for hormones
what is the function of protein attached proteins?
enzymes
how can we form a lipid anchored protein to the bilayer? 3 ways
amide linkage, esterify a protein with a cysteine residue, and also with a thioether
what are the five ways we can move things across the membrane
simple diffusion, facilitated diffusion, gated channels, active transport, vesicular transport
what can diffuse across the membrane?
NO, water, very small molecules like gases and lipid soluble substances
what uses facilitated diffusion?
no energy required, so molecules like glucose (many hydrophilic portions) with assistance by a carrier or transport protein; also bicarbonate; keep in mind that there is an equilibration in concentration on both sides
example of gated channels?
cystic fibrosis dictates how much Cl- is on one side of the cell membrane; other examples include voltage gated channels, like nerve cells, ligand gated channels(responding to binding of ligand to protein and in this the cystic fibrosis like mentioned above), phosphorylation gated channels responding to covalent change in voltage across the membrane
how does hypercholesterolemia affect the cell?
not enough cholesterol receptors so high levels accumulate in the blood
What are gap junctions?
gated type of cell that allow sharing of metabolic activity, important for cells isolated from circulatory like lens of the eyes depending on gated channels to share metabolic activity and heart cells. Like if big change in pH or calcium, channels can be opened or closed
what are the three types of vesicular transport?
pinocytosis, phagocytosis, receptor mediated endocytosis
what is phagocytosis?
cell membrane encloses around a solid particle like for white blood cells
what is pinocytosis?
when the receptor forms around the fluid containing dispersed molecules
what is receptor mediated endocytosis?
the name given to the formation of clathrin coated vesicles that mediate the internalization of membrane bound receptors whose primary function is to receive nutrients
what is exocytosis?
refers to the vesicular transport out of the cell whose primary function is to expel waste
when referring to the plasma membrane we view it as a fluid mosaic model, though it is very organized adding to the complexity of it. Why?
the idea is that its composition both laterally and horizontally between the two leaflets is not random, no uniform distribution of lipids and proteins and we have this idea of lipid rafts.
what are lipid rafts?
assemblies of different amounts of sphingolipids, cholesterol, and proteins that aggregate most often transmembrane protein involved in signal transduction. If all in the same raft then dimerization occurs and signals can be propagated
what would happen if some lysosomal enzymes found there way into the cytoplasm?
they wound not be able to function well because pH is different. Also keep in mind that lysosomal enzymes have to be imported into the lysosomes
what is an example of lysosomal storage disease?
Tay Sachs disease (an accumulation of partially digested gangliosides in lysosomes) and Pompe disease (accumulation of glycogen particles in lysosomes) Gaucher Disease, Hurler Syndrome, I-Cell Disease
why are mitochondrial disorders are rare?
first, we inherit mitochondrial genes them from our maternal mother and all children who inherit defective mitochondria will express some component of disease (mild to severe) affecting nervous system or muscle function.
What is an example of mitochondrial disorders?
Leber hereditary optic neuropathy and Myoclonic epilepsy with ragged red fibers (MERRF)
what is the largest sub cellular organelle?
Nucleus, which houses the genome of the cell
what is the nucleus primary function?
DNA replication, transcription, and ribosome assembly (nucleolus).
what is the nucleolus?
a substructure of the nucleus, the site of rRNA transcription and processing of ribosome assembly
what is important about genome folding?
the genome is so large that all 3 m of DNA need to be folded into a small space like a couple micrometers. If done incorrectly, knots can occur and errors happen affecting proper cell division.
what is progeria?
rapid aging for kids and die young of diseases like heart disease. This is due to the inability of the nuclear envelope to anchor chromosomes that would otherwise prevent knots from forming
what is the smooth ER used for?
lipid synthesis, toxin metabolism, hydrophobic molecule synthesis, glycogen storage
what is the rough ER used for?
protein synthesis, post-translational modifications
name the two peroxisomal disorders discussed in class?
Adrenoleukodystrophy (intermediate) and Zellweger Syndrome
What is Adrenoleukodystrophy?
This is when you have peroxisomal oxidation of very long chain fatty acids, these accumulate in the nervous system and adrenal glands and interfere with nerve function b/c of the disruption in myelin sheath
What is Zellweger Syndrome?
classic peroxisomal biogenesis disorder - usually because of the failure of the body to produce peroxisomes that function properly - with distinctive dysmorphic features like a prominent forehead, hypertelorism, large fontanelle; this is fatal in infants
what are ribosomes?
intracellular organelles used for protein synthesis
what are prokaryotes?
single cells surrounded by a cell membrane and a cell wall exterior to the membrane; they are prokaryotes not containing nuclei or other organelles (membrane surrounded sub cellular structures) Gram Positive and negative bacteria, gram positive retains the dye. Gram negative is disease causing
What is the internal compartmentalization of membranes?
membranes are lipid structures that separates the contents of the compartment they surround from the environment. Cell organelles have membranes that separate themselves from the cytoplasm and also membranes concentrate enzyme for a particular function. This is controlled by transporters and receptors
