Cells Flashcards

Questão	Responda
Channel proteins	provide passageway through membrane for hydrophilic (water-soluble) substances (polar, and charged).
Recognition proteins	such as major-histocompatibility complex on macrophage to distinguish between self and foreign; they are glycoproteins due to oligosaccharides attached.
Ion channels	passage of ions across membrane. Called gated channels in nerve and muscle cells, respond to stimuli. Note that these can be voltage-gated (respond to difference in membrane potential), ligand-gated (chemical binds and opens channel), or mechanically-gated (respond to pressure, vibration, temperature, etc).
Porins	allow passage of certain ions + small polar molecules. Aquaporins increase rate of H2O passing (kidney and plant root cells). These tend not to be specific, they’re just large passages, if you can fit you’d go through.
Carrier Proteins	bind to specific molecules, protein changes shape, molecule passed across. E.g. glucose into cell.(this is a type of transport protein). Carrier seems to be specific to movement across membrane via integral membrane protein.
Transport proteins	can use ATP to transport materials across (not all transport use ATP). Active transport. E.g. Na+-K+ pump to maintain gradients. Facilitated diffusion as well. Transport protein is a broad category that encompasses many of the above. Chad’s quiz says transport use ATP but other sources contradict: transport can by facilitated diffusion.
Adhesion proteins	attach cells to neighboring cells, provide anchors for internal filaments and tubules (stability)
Receptor proteins	binding site for hormones + other trigger molecules
Cholesterol	adds rigidity to membrane of animal cells under normal conditions (but at low temperatures it maintains its fluidity); sterols provide similar function in plant cells. Prokaryotes do not have cholesterol in their membranes (use hopanoids instead)
Glycocalyx	: a carbohydrate coat that covers outer face of cell wall of some bacteria and outer face of plasma membrane (some animal cells). It consists of glycolipids (attached to plasma membrane) and glycoproteins (such as recognition proteins). It may provide adhesive capabilities, a barrier to infection, or markers for cell-cell recognition
Nuclear Lamina	dense fibrillar network inside nucleus of eukaryotic cells (Intermediate filaments + membrane assoc. proteins). Provides mechanical support; also helps regulate DNA replication, cell division, chromatin organization.
Ribosomes	60S + 40S = 80S, prokaryote (50S + 30S = 70S); the two subunits produced inside the nucloleus moved into the cytoplasm where they assembled into a single 80S ribosomes (larger S value indicates heavier molecule). Made of rRNA+protein, function to make proteins
Cytosol	difference vs cytoplasm here (cytosol doesn’t include the stuff suspended within the gel-like substance, it is JUST the gel-like stuff. Think jello vs veggie stew.) (the cytosol is also known as cytoplasmic matrix)
Endoplasmic Reticulum	: rough ER (with ribosomes) creates glycoproteins by attaching polysaccharides to polypeptides as they are assembled by ribosomes. In eukaryotes the rough ER is continuous with the outer nuclear membrane. Smooth ER (no ribosomes) synthesizes lipids and steroid hormones for export. In liver cells, smooth ER has functions in breakdown toxins, drugs, and toxic by-products from cellular rxn. Smooth and striated muscle have smooth ER’s called sarcoplasmic reticulums that store and release ions, e.g. Ca 2+
Lysosomes	vesicles produced from Golgi that contain digestive enzymes (low pH for function); break down nutrients/bacteria/cell debris. Any enzyme that escape from lysosomes remains inactive in the neutral pH of cytosol (other source says autolysis) (lysosomes in plant cell – maybe, but generally taught as none). Functions in apoptosis (releases contents into cell).
Golgi aparatus	transport of various substances in vesicles (cis face is for incoming vesicles, trans face for secretory vesicles). Has flattened sacs known as cisternae
Peroxisomes	break down substances (H2O2 +RH2 => R + 2H2O), fatty acid, and amino acid; common in liver and kidney where they break toxic substances. In plant cell, peroxisomes modify by-products of photorespiration.
Microtubules	made up of protein tubulin, provide support and motility for cellular activities; spindle apparatus which guide chromosomes during division; in flagella and cilia (9+2 array; 9 pairs + 2 singlets in center) in all animal cells and lower plants (mosses, ferns).
Microfilaments	made up of actin and involved in cell motility. (skeletal muscle, amoeba pseudopod, cleavage furrow)
Intermediate filaments	provide support for maintaining cell shape. E.g. keratin
Central vacuoles	large, occupy most of plant cell interior, exert turgor when fully filled to maintain rigidity. Also store nutrients, carry out functions performed by lysosomes in animal cells. Have a specialized membrane (tonoplast)
Contractile Vacuoles	in single-celled organisms that collect and pump excess water out of the cells (prevent bursting). Active transport. Found in Protista like amoeba and paramecia, organisms live in hypotonic environment.
Cell walls	found in plants, fungi, protists, and bacteria (cellulose in plants; chitin in fungi; peptidoglycans in bacteria, polysaccharides in archea). Provides support. Sometimes a secondary cell wall develops beneath the primary one.
Plastids	found in plant cells. Chloroplasts (site of photosynthesis), leucoplasts (can specialize to store starch/lipid/protein as amyloplasts/elaioplasts/proteinoplasts respectively, or serve general biosynthetic fxns), chromoplasts (store carotenoids)
Mitichondria	make ATP, also fatty acid catabolism (B-oxidation)! (fatty acids are made in cytosol). Also have their own circular DNA and ribosomes (gives rise to endosymbiotic theory!). Have a double layered membrane.
Anchoring junctions	desmosome (keratin filaments inside attach to adhesion plaques which bind adjacent cells together via connecting adhesion proteins, providing mechanical stability, hold cellular structures together). In animal cells. Present in tissues with mechanical stress – skin epithelium, cervix/uterus.
Tight junctions	completely encircles each cell, producing a seal that prevents the passage of materials between cells; characteristic of cells lining the digestive tract where materials are required to pass through cells into blood (They prevent the passage of molecules and ions through the space between cells. So materials must actually enter the cells (by diffusion or active transport) in order to pass through the tissue). In animal cells.
Gap junction	narrow tunnels between animal cells (connexins); prevent cytoplasms of each cell from mixing, but allow passage of ions and small molecules; essentially channel proteins of two adjacent cells that are closely aligned (smooth muscle single of spreading action potential). In animal cells. Tissue like heart have these to pass electrical impulses

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	Criado por Foster Parnell mais de 9 anos atrás