Ch 3. Cell membranes and organelles
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89 terms
Terms | Definitions |
|---|---|
 organelles | specialized structures in cells used to carry out various functions. Only in eukaryotes |
| fluid-mosaic model | the cell membrane is semi-permeable, consising of a double layer of phospholipids, which have a hydrophilic phosphate head and a hydrophobic fatty acid tail. Heads on outside, tails on inside |
| four major phospholipid types in mammalian cells | phosphotidylcholine, sphingomyelin, phosphotidylserine and phosphotidylethanolamine. All have neutral charge except with serine |
| phosphotidylinositol | lipid that is essential in cell signaling, used to convert nonsteroid hormone messages into "second messages" sent into the cel cytoplasm |
| ganglioside | an example of a glycolipid in cell membrane. May aid in electrical impulses along cel membranes and cell-to-cell recognition |
| What do most proteins/phospholipids associated with the plasma membrane have associated with them? | carbohydrate groups/sugars. The plasma membrane is extremely sugar rich |
| What is the most favorable configuration for the amino acid region that crosses within the hydrophobic membrane interior? | alpha helix because it allows the protein to "hide" the polar peptide bonds that link the amino acids, which causes the nonpolar amino acid side chains to stick out, which works well with hydrophobic fatty acid tails. |
| glycocalyx | the protein- and carbohydrate-rich coating on the cell surface |
| What are two factors that determine whether or not a molecule will be able to pass through a cell's membrane? | size and polarity. Those that are small and nonpolar will have easiest time getting through |
| What are three transport mechanisms for molecules through the cell membrane? | simple difussion, facilitated diffusion and active transport |
| simple diffusion | movement of particles from higher concentration to lower concentration. No energy required! |
| Examples of molecules that can move through layer via simple diffusion | water, carbon dioxide, oxygen |
| Osmosis | simple diffusion when it occurs with water. Higher water concentration (low salt) to lower water concentration (high salt) |
| hypotonic solution | where salt concentration is high compared to surroundings (water rushes in) causes swelling |
| hypertonic solution | where salt concentration is low compared to surroundings (water rushes out) causes shrinking |
| isotonic solutions | when there an equal salt concentration compared to surroundings |
| facilitated diffusion | uses channels, aka passive transport |
| what type of charge does the cytoplasm have? what ions are favored to move by facilitated diffusion | negatively charged, positively charged ions |
| electrochemical gradient | combination of solute concentration and electrical gradient |
| active transport | use energy of ATP to change conformation in membrane so molecules can be brought into and out of cell AGAINST concentration gradients. |
| ATPase pumps | provide maintenance of unequal concentrations of cetain ions across the lipid bilayer |
| example of an active transport | sodium-potassium ATPase membrane pump. uses the energy of ATP breakdown to pull in 2 potassium ions and kick out 3 sodium ions |
| antiport | one molecule goes in, another goes out |
| symport | two molecules go in/out at same time |
| Where is calcium stored in the cell? | It is in high concentration in endoplasmic reticulum, and low concentration in cytoplasm |
| calcium-ATPase pumps | in the ER membrane, actively transport calcium to ER |
| What can the calcium gradient in the ER be used for? | by muscle cells to regulate muscle contraction |
| endo and exocytosis | used to move large molecules through the cell membrane. Invagination of cell membrane to make vesicle |
| what are the three types of cell junctions? | tight junctions, desmosomes, gap junctions |
| tight junctions | aka occluding junctions. so tight that nothing can diffuse between the cells or past the junction. Privide barrier to transport |
| example of a useful place for tight junction | intestines because cells absorb nutrients from one side of cell and transport them out to the other side, tight junctions prevent the nutrients from leaving the cell once inside |
| what types of cells use anchoring junctions? | cells subjected to stress |
| anchoring junctions | hold cells together |
| an example of cells with anchoring junctions | desmosomes in epithelial/heart cells |
| what is another name for communicating junctions | gap junction |
| what types of proteins form gap junctions? | connexins, form tubes between cells cytoplasms |
| what types of signals are transmitted with gap junctions? | undisrupted and very fast signal transmission |
| examples of cells with gap junctions | ex. heart, muscle contraction, fish tail flip |
| connexeon | complex of many connexin proteins |
| plasmodesmata | glant cells equivalent of gap junctions, allow flow of nuclei from one cell to another. |
| what can plant viruses do? | exploit plasmodemata, virus particles can spread rapidly from one section to another |
| nucleus | largest organelle of animal cell. |
| nuclear envelope | separates the nucleus from the rest of the cell. Double membrane with nuclear pores for communication. very selective |
| what allows proteins to enter nucleus | special sequences in protein |
| nucleolus | assembles ribosomal RNA (rRNA) whcih is taken to cytoplasm for protein synthesis |
| what process is not done in nucleus? | energy production |
| ribosomes | involved in protein production. One large and one small subunit |
| where are ribosomes made? | in nucleolus |
| where can you find ribosomes | free ribosomes in cytoplasm and bound ribosomes in the outermembrane of ER |
| which organelles have their own ribosomes for protein synthesis? | mitochondria and chloroplasts. They more closely resemble prokaryotic ribosomes |
| rough ER | has ribosomes lining outer surface, invoved in protein synthesis |
| lumen | the interior of the ER between membrane layers, at some points its continuous with nuclear envelope |
| smooth ER | no ribosomes, involved in lipid synthesis and drug detoxification |
| what types of proteins are made by ribosomes in the rough ER? | proteins that are secreted, found in the cell membrane, the ER or the Golgi |
| what type of amino acid sequence on the amino terminus of proteins determines its fate? | a hydrophobic sequence of amino acids |
| what is special about proteins that will be secreted? | they have one hydrophobic signal sequence, they will be inserted into the ER lumen when synthesized and then released from cell later |
| what is special about proteins that are destined to be membrane bound? | They have hydrophobic transmembrane domains that are threaded through the rough ER membrane as protein is synthesized |
| what is another function of ER membrane besides protein synthesis? | budding off to form vesicles that have newly synthesized proteins, they head for golgi |
| location of golgi apparatus | located between the ER and plasma membrane |
| location of cis golgi | stacks of golgi apparatus closest to ER |
| location of trans golgi | stacks of golgi farthest from ER, closest to plasma membrane |
| What part of golgi do vesicles from ER fuse to? | fuse with cis golgi |
| Give an example of a role of the golgi | carries out postranslational modification of proteins through glycosylation (adding sugar groups to proteins) so they can go to plasma membrane |
| how do proteins move from stack to stack in cis golgi? | they are packaged in vesicles and as they move, they fuse with the stack and release contents. |
| what happens to proteins in trans golgi? | they are sorted into vesicles bsed on signals on the proteins that indicate their destination |
| lysosomes | contain hydrolytic enzymes that break down the various biological molecules to their building blocks to be used in new synthesis |
| What is the pH inside the lysosome? | slightly acidic, pH 5, optimal for enzymes. This is kept separate by lysosome membrane |
| what is special about peroxisomes? | contain oidative enzymes that catalyze reactions where hydrogen peroxide (toxic) is created and then destroyed. |
| what do peroxisomes break down? | fats into small molecules to be used for fuel, in liver used to detoxify alcohol |
| mitochondria | source of energy and site of aerobic respiratin |
| What is special about mitochondria phospholipid bilayer membrane? | it has many pares that allow some molecules to enter on the basis of their size |
| cristae | the internal compartments formed by the inner membrane of a mitochondrion |
| matrix of mitochondria | the area bounded b the innermembrane, site of reactions involved in cell respiration (electron transport, krebs cycle and ATP production) |
| What is unique about mitochondria? | They contain their own circular DNA and ribosomes, both of which resemble those of prokaryotes. They can self-replicated through binary fission |
| endosymbiotic hypothesis | the theory that mitochondria developed from prokaryotic cells, providing energy to host cell and protection from environment (symbiosis) |
| what is one major organelle that animal cells have but plant cells do not? | centrioles |
| chloroplasts | only in plant cells and protist. Function in photosynthesis, have their own DNA and ribosomes |
| thylakoids | membrane sacs inside chloroplast |
| grana | the stacks in the thylakoids tht are derived from the inner membrane |
| stroma | the floid inside the chloroplast surrounding the grana |
| Where is the chlorophyll of the cell located? | in the thylakoid membranes |
| What are the specialized plant organelles? | chloroplasts, large vacuoles, cellulose cell wall |
| vacuoles | membrane-enclosed sacs within cells. In plants, they can take up to 90% of the cell volume. Store waste products |
| What is the difference between genome in prokaryotes and eukaryotes? | pro- small, circular, no histones. Euk- large segmented chromosomes with histones, packaging |
| where does ATP production occur in prokaryotes v eukaryotes? | pro- plasma membrane, euk- mitochondria |
| what is the difference between flagella in prokaryotes vs eukryotes? | pro- unique structure, euk- with microtubules |
| What is the diff between RNA processing in prokaryotes vs eukaryotes? | pro- no splicing, euk- 5-cap, poly-A tail, mRNA splicing |
| Where does transcription and translation occur in pro- vs euk-? | pro- together in cytosol, euk- separate |
| Difference between cytoskeleton of pro- and euk-? | pro- do not have cytoskeleton, euk- do have one |
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