cell membrane and cytoplasm

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  1. Major features of prokaryotic cell 4
    No nuclear envelope

    No membrane bound organelles

    No cell wall and no cytoskeleton

    Smaller than eukaryotic cells
  2. Organelle define
    Subcellular compartment or large macromolecular complex, often membrane

    enclosed but doesn’t have to be, so long as it has a distinct structure, composition, and function
  3. major features of eukaryotic (animal) cell 3
    DNA enclosed in nuclear envelope (nucleus and cytoplasm(surrounds nucleus) is divided into 2 main compartments

    Internal membrane bound organelles

    Cytoskeleton and no cell wall
  4. 2 major features of eukaryotic cell (plant)
    Chloroplasts

    Cell wall made of cellulose
  5. Antibiotic define
    A soluble substance derived from a mold or bacterium that inhibits the growth of other microorganisms, many times by fitting in the active site of an enzyme
  6. How do antibiotics skills bacteria and not your cells?
    They target either bacterial enzymes that have no eukary counterpart or bacterial enzymes (like in protein synthesis) whose structure is different enough from their eukaryotic counterparts such that the antibiotic kills bacteria but not you
  7. How light microscopy is used?
    light is focused on a specimen by a glass condenser lens; the image is then magnified by an objective lens and an ocular lens, for projection on the eye, digital camera, digital video camera, or photographic film
  8. how electron microscopy is used?
    a beam of electrons (top of the  microscope) is used instead of light, and electromagnets are used instead of glass lenses. The electron beam is focused on the specimen by a condenser lens; the image is magnified by an objective lens for projection on a digital detector, fluorescent screen, or photographic film **better at resolving smaller objects
  9. micrograph
    photo taken by means of a microscope

    **prokaryotes are .2-2 microns in diameter

    **eukaryotes are 10-100 microns in dimeterImage Upload
  10. Cell membranes 3 main components
    Phospholipids

    Cholesterol

    Proteins

    **cell membranes range from 7.50nm in thickness so they can only be viewed under an electron microscope
  11. 3 part structure of phospholipids
    Polar head group

    Linkage derived from glycerol

    2 nonpolar fatty acid tails

    **can be saturated and unsaturated, in humans phospholipids contain 1 saturated and one unsaturated FA tails

    ** saturated straight unsaturated kink
  12. 4 most abundant types of phospholipids in human membranes
    Phosphatidylcholine

    Sphingomyelin (linkage derived from sphingosine not glycerol)

    Phosphatidylserine(only phosphor with negative charge and gives itself a special function

    Phosphatidylethanolamine

    **all major classes of phospholipids are synthesized on smooth ER
  13. 2 actions phospholipids perform when placed into water
    Form a lipid bilayer by putting hydrophilic head groups next to water and bury hydrophobic tails away from water

    **water above and below bilayer prevents membrane lipids from escaping from bilayer, but the phospholipids move around and change places with one another spontaneously or move laterally, rotate, or flex.

    **it is not energetically favored to drag large hydrophilic head group through the hydrophobic center of the bilayer
  14. Fluidity define
    Speed at which movements occur (to phospholipids, cholesterol, or proteins)

    **composition of membranes affect fluidity
  15. Double bond in unsat fatty acyl tail causes bend in tail, causes phospholipids to stay further apart and be more fluid

    Unsaturated fatty acyl tails on phospholipids increase membrane fluidity, Saturated tails on  phospholipids decrease membrane fluidity
  16. 2 reasons why membranes have to be fluid to work properly
    • Membrane traffic in cell, membranes have to be fluid enough to change their shape and be able to bud off a vesicle
    • Be fluid enough to have a vesicle fuse with a target membrane and have its lipid and membrane components spread out in the bilayer after fusion
  17. Cholesterol structure and function
    One smaller polar head group and one fatty acid tail Cholesterol molecules immobilize the first few


     

    hydrocarbon groups of the phospholipid molecules but the smaller polar head group allows cholestersol to flip easily between 2 bilayers and will be distributed equally in every membrane

    Tends to “stiffen” cell  membranesThis makes the lipid bilayer less deformable and decreases its permeability to small water soluble molecules

    **Cholesterol is absolutely essential for every membrane in every cell in your body, you don’t ingest it, your body will synthesize it on SER (cells needed a lot of membrane cholesterol or steroid hormones have more SER), it is also a precursor for steroid hormones

    **Bacteria and plant cells do not contain cholesterol*, this is why bacteria need a cell wall to maintain rigidity of membrane
  18. How temperature effects cholesterols fluidity?
    Warm temperature, cholesterol restrains movement of phospholipids (high cholesterol decrease fluidity)

    Cool temperature maintain fluidity by preventing tight packing
  19. Image Upload
    **membranes are composed of lipids with embedded proteins 1:1 ratio
  20. 2 types of membrane function and location
    Integral membrane proteins – embedded in membrane need detergent to remove

    Peripheral membrane proteins – only help to membrane by ionic interactions with membrane proteins or lipids, can be washed away with high salt rinse
  21. 3 structures of representative integral membrane proteins and their structures helices
    Glycophorin – human red blood cell protein has a single transmembrane alpha helix (2 copies form dimer)

    Bacteriorhodopsin – a light driven proton pump from the plasma membrane of a purple bacterium has 7 transmembrane helices

    Porin – nonselective channel protein from the outer membrane of a bacterium or mitochondria

    **aa in transmembrane domain are hydrophobicImage Upload
  22. Characteristics of integral membrane protein 6
    Alpha helix containing about 20 AA is required to completelty transverse a membrane

    These amino acids need to have hydrophobic side chains to be able to cross the hydrophobic interior of the bilayer

    Both lipids and proteins may be mobile or fluid in the plane of the membrane

    BUT Transmembrane proteins will also not flip spontaneously (like phospholipids) between leaflets of the bilayer because of all the charge

    Membranes composed of just phospholipids spontaneously repel large and/or hydrophilic molecules

    Use regulated ion channels to control which ions cross membranes
  23. 6 functions of membranes and membrane proteins
    Transport of molecules – channels and pumps

    Cell signaling – cell membrane bound receptors, enzymes, and proteins

    Phagocytosis, pinocytosis, receptor medited endocytosis

    Cell to cell communication – due to presence of carbohydrates

    Attachment to cytoskeleton and extracellular matrix

    Compartmentalization – segregates one part of the cell from other
  24. 2 types of transport proteins
    A protein spanning the membrane may provide hydrophilic channel across that is selective for a particular solute

    One transport protein shuttles a substance from one side to the other by changing shape by hydrolyzing ATP as an energy source to pump across membrane
  25. Channelopathies defined Pathy = suffering or disease
    Diseases caused by disturbed function of ion channel subunits or the proteins that regulate them
  26. Many mutation sites may cause similar channelopathy, what 2 ways can channelopathies occur?
    Congenital – resulting in mutation or mutations in the encoding genes

    Acquired – often resulting from auto immune attack on an ion channel
  27. Cystic fibrosis transmembrane conductance regulator function
    Is a transmembrane protein with 12 transmem domains that transports chloride ions into and out of epithelial cells into the lumen
  28. Cystic fibrosis define
    Repeated chest infections cause progressive loss of lung function and major cause of premature death and is caused by mutations in CFTR
  29. Simplified cystic fibrosis
    Normal cell lining respiratory tract secrete proteins into lumen of airway, with defective CFTR the chloride imbalance within cell causes cell to secrete less water, cells swell, tissue damage, secretions become thick, the secretions clog up respiratory tract and trap bacteria leads to lung infections
  30. Cell signaling defined
    Receptor (membrane protein) may have a binding site with a specific shape that fits the shape of a chemical messenger (i.e hormone). The signaling molecule (external messenger) may cause the protein to change shape allowing it to relay a message inside usually by binding to a cytoplasmic protein.

    A signaling molecule can bind to the receptor which can activate one or more intracellular signaling pathways with series of signaling proteins. One or more of the intracell signaling proteins can alter the activity or effector proteins and thereby the behavior of the cell
  31. Lipid rafts form a thick bilayer that are formed by 3
    Sphingomyelin

    Glycolipids

    Cholesterol

    **they float around but fluidity within is diminished
  32. Charatceristics of lipid rafts lipids
    Sphingomyelin has 2 saturated FA tails, causes less fluidity in lipid raft

    Need 24-25 hydrophobic AA to cross lipid raft, transmem proteins with longer domains cluster in lipid rafts as well as signaling proteins
  33. Ways in which lipid rafts control cell signaling?
    Rafts may contain incomplete signaling pathways that are activated when a receptor or other molecule is recruit into the raft

    Rafts can limit signaling by physical sequestration  (being kept apart) of signaling components to block nonspecific interactions or by suppressing the intrinsic activity of signaling proteins within rafts

     

    Singal transduction in lipid rafts occurs more rapidly and efficiently because of close proximity of interaction proteins. Different signaling rafts allow for separation of specific signaling molecules from each other
  34. Phagocytosis-cell eat

    Pinocytosis-cell drink

    Receptor mediated endocytosis-breakdown specific ligands by engulfing them and then pinching them off **clathrin coated pits and vesicles carry out RME
  35. How are faces of cellular membranes conserved during membrane budding and fusion?
    During endocytosis, segment of plasma mem buds inward toward the cytosol so the exoplasmic face is inside facing the vesicle lumen while the cytosolic face is on the outside. During exocytosis, an intracellular vesicle fuses with plasma membrane and the exoplasmic face connects with the extracellular medium. Whatever is facing what will eventually end there once the process is complete
  36. Caveolae defined and function
    Lipid raft protein coating that forms the organelle caveola in most cell types but are abundant in endothelial cells lining blood capillaries

    It also carries macromolecules from blood stream across capillary endothelial cell and into the extracellular fluid and vice versa. Can pinch off and bring a macromolecule into the cell one type of endocytosis that is not clathrin-mediated

    **if the vesicles go all the way across the cell and fuse with the other side its call transcytosis, caveolae do this
  37. Cell to cell communication have membrane carbohydrates that do what
    are attached to glycoproteins lipids (glycolipids) and play a key role in cell-cell recognition
  38. How cell-cell recognition occurs with membrane carbohydrates? 3
    Ability of a cell to distinguish neighboring cells from each other

    Important in organ and tissue development

    Basis for rejection of foreign cells by immune system
  39. Extracellular matrix function and characteristics
    Nonliving material secreted by cells that fills spaces between the cells in tissue, protecting them and holding them together

    May be semifluid or regidy and hard as in bone

    Is composed mainly of proteins (i.e collagens, elastin, glycoproteins,fibronectin,laminins and osteoporins
  40. Cytoplasm define
    Contents of a Contents of a cell that are contained within its plasma membrane but, in the case of eukaryotic cells, outside the nucleus
  41. Cytosol define
    Contents of the main compartment of the cytoplasm excluding membrane bounded organelles such as endoplasmic reticulum and mitochondria

    **70% of cell volume, gelatinous substance, consists of cytoskeleton filaments, organic molecules, free proteins like enzymes, fatty acids, sugars and AA, salts and water. Contains ribosomes, proteasomes, and nonmembrane bound cytoplasmic inclusions
  42. 3 common types of cytoplasmic inclusions
    Fat droplets

    Lipofuscin granules

    Glycogen rosettes
  43. Characteristics of cytoplasmic inclusions
    Not membrane bound

    Composed of accumulated metabolites or other substances and are oftem transitory components of the cytoplasm

    Nonmotile with no metabolic activity

    Not an organelle since they don’t do anything
  44. Glycogen rosettes (granules) function and characteristics4
    Stored E source

    Aggregates of a carbohydrate polymer in which glucose is stored

    Not surrounded by membrane

    Liver cells and skeletal muscles are 2 major glycogen storage sites

Card Set Information

Author:
kaitiek09
ID:
333935
Filename:
cell membrane and cytoplasm
Updated:
2017-09-05 13:59:58
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medical
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Description:
RUSM cell membranes and cytoplasm WEEK 1 FUNDAMENTALS 1
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