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DAT Biology > 2. Cells > Flashcards

2. Cells Flashcards

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1
Q

Peripheral Proteins

A
  • attached loosely to inner or outer surface of membrane
  • generally hydrophilic, held in place by H bonding and electrostatic interactions, disrupt/detach by changing salt conc or pH to disrupt these interactions.
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2
Q

Integral Proteins

A
  • extend into the membrane
  • like phospholipids, integral proteins are amphipathic
  • use detergent to destroy membrane and expose these proteins
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3
Q

Transmembrane Proteins

A
  • integral proteins spanning across membrane, appearing at both sides
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4
Q

Fluid Mosaic Model

A
  • mosaic nature of scattered proteins within a flexible matrix of phospholipid molecules
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5
Q

Membrane Permeability

A
  • small, uncharged, nonpolar molecules (polar can only if small and uncharged, and hydrophobic molecules can freely pass. everything else requires transporter
  • large, polar (such as glucose) and all ions are impermeable.
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6
Q

Plasma Membrane Proteins

Channel Proteins

A
  • provide passageway through membrane for hydrophilic substances
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7
Q

Plasma Membrane Proteins

Recognition Proteins

A
  • give each cell a unique identification
  • are glycoproteins bec they have short polysaccharide chains (oligosaccharides). oligosaccharide part extends away from the surface of the membrane.
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8
Q

Plasma Membrane Proteins

Ion Channels

A
  • passage of ions across membrane
  • called gated channels in nerve and muscle cells, respond to stimuli
  • can be voltage gated (respond to diff in membrane potential), ligand gated (chemical binds and opens channel), or mechanically gated (respond to pressure, vibration, temperature, etc
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9
Q

Plasma Membrane Proteins

Porins

A
  • allow passage of certain ions + small polar molecules. - aquaporins increase rate of H2O passing (kidney and plant root cells). Usually not specific, if you fit, you can go through.
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10
Q

Plasma Membrane Proteins

Carrier Proteins

A
  • bind specific molecules, protein changes shape, molecules passes across, glucose into cell (type of transport protein)
  • specific to movement across membrane via integral membrane protein
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11
Q

Plasma Membrane Proteins

Transport Proteins

A
  • can use ATP to transport materials across (not all use ATP).
  • active transport. Na+ K+ pump to maintain gradients.
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12
Q

Plasma Membrane Proteins

Adhesion Proteins

A
  • attach cells to neighbors, provide anchors for internal filament and tubules (stability)
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13
Q

Plasma Membrane Proteins

Receptor Proteins

A
  • binding site for hormones + other trigger molecules
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14
Q

Cholesterol

A
  • adds rigidity to membrane of animal cells under normal conditions
  • sterols provide similar functions in plant cells
  • prokaryotes do not have cholesterol in membranes
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15
Q

Glycocalyx

A
  • carbohydrate coat that covers outer surface of cell wall of some bacteria and outer face of plasma membrane of some animal cells.
  • consists of glycolipids (attached to plasma membrane) and glycoproteins (such as recognition proteins.
  • may provide adhesive capabilities, barrier to infection, or markers for cell-cell recognition.
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16
Q

Organelles

A
  • bodies within cytoplasm that serve to physically separate various metabolic reactions that occur within cells
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17
Q

Nucleus

A
  • chromatin is general packaging structure of DNA around proteins in eukaryotes
  • chromosomes is tightly condensed chromatin when cell is ready to divide
  • histones serve to organize DNA which coil around into bundle nucleosomes (8 histones)
  • nucleolus make ribosomes (rRNA). rRNA synthesized in nucleolus + ribosomal proteins imported from cytoplasm -> ribosomal subunits form; subunits exported to cytoplasm for final assembly.
  • nucleus bound by double layer nuclear envelope w/ nuclear pores for transport (mRNA, ribosome subunits, dNTPs, RNA polymerase, histones, etc.)
  • no cytoplasm in nucleus, there is a nuceloplasm instead
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18
Q

Nuclear Lamina

A
  • dense fibrillar network inside nucleus of euk. cells (intermediate filaments + membrane assoc. proteins). provide mechanical support; also help regulate DNA replication, cell division, chromatin organization.
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19
Q

Nucleoid

A
  • irregular shaped region in prokaryotes containing all/ most genetic material
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20
Q

Cytoplasm

A
  • area not structure
  • metabolic activity and transport occur here.
  • Cyclosis is streaming movement within cell. Doesn’t include nucleus, but does include cytosol, organelles, everything in cytosol but nucleus.
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21
Q

Cytosol

A
  • cytosol doesn’t include the stuff suspended within the gel-like substance. it is just the gel like stuff.
  • Also known as cytoplasmix matrix.
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22
Q

Ribosomes

A
  • Eukaryotes: 60S + 40S = 80S
  • Prokaryotes: 50S + 30S = 70S
  • The two subunits produced in nucleolus and move to cytoplasm for assembly.
  • Larger S indicates heavier molecule
  • Made from rRNA + protein, function to make proteins.
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23
Q

ER

A
  • Rough ER: contains ribosomes. creates glycoproteins by attaching polysaccharides to polypeptides as they’re assembled by ribosomes.
  • In euk. rough ER is continuous w/ outer nuclear memb.
  • Smooth ER (no ribosomes): synthesize lipids and steroid hormones for export. In liver cells, smooth ER breakdown toxins, drugs, and toxic by-products from cellular reactions.
  • Smooth and striated muscle have smooth ER called sarcoplasmic reticulum that store and release ions, Ca+2.
24
Q

Lysosomes

A
  • vesicles produced from Golgi that contain digestive enzymes (low pH); breakdown nutrients/bacteria/cell debris
  • functions in apoptosis (release contents into cell)
  • not found in plant cells
25
Q

Golgi

A
  • transport of various substances in vesicles.
  • cis face for incoming vesicles.
  • trans face for secretory vesicles
  • Has flattened sacs known as cristernae.
26
Q

Peroxisomes

A
  • breakdown substances, fatty acid, and amino acid, common in liver and kidney where they break toxic substances
  • in plant cells, peroxisomes modify by-products of photorespiration.
  • In germinating seeds, it is called glyoxysomes -> breakdown stored fatty acids to generate energy for growth.
  • Peroxisomes produce H2O2 which they can use to oxidize substrates, and can breakdown H2O2 if necessary
27
Q

Microtubules

A
  • protein tubulin
  • support and motility for cellular activities; spindle apparatus, flagella and cilia (9+2 array, 9 pairs + 2 singlets) in all animal cells and lower plants (mosses, ferns)
28
Q

Intermediate Filaments

A
  • support for maintaining cell shape, e.g. keratin
29
Q

Microfilament

A
  • actin

- cell motility (skeletal muscle, amoeba pseudopod, cleavage furrow)

30
Q

Microtubules Organizing Centers (MTOCs)

A
  • centrioles (9X3), pair of centrioles in centrosome give rise to microtubules of spidle apparatus
  • basal bodies: base of each flagellum and cilium and organize their development. 9x3 array
  • plant cells lack centrioles and its division is by cell plate instead of cleavage furrow - plants do have MTOCs
31
Q

Transport Vacuoles

A
  • transport materials between organelles or organelles and plasma membrane
32
Q

Food vcauoles

A
  • temporary receptacles of nutrients; merge with lysosomes which breakdown food.
33
Q

Central Vacuoles

A
  • large, occupy most of plant cell interior.
  • exert turgor when fully filled to maintain rigidity.
  • store nutrients, carry out functions performed by lysosomes in animal cells
  • have a specialized membrane (tonoplast)
34
Q

Storage Vacuoles

A
  • plants store starch, pigments, and toxic substances (nicotine)
35
Q

Contractile Vacuoles

A
  • in single celled organisms that collect and pump excess water out of cells (prevent bursting)
  • active transport
  • found in protista like amoeba and paramecia, organisms that live in hypotonic environment.
36
Q

Cell Walls

A
  • found in plants, fungi, and bacteria
  • plants: cellulose
  • fungi: chitin
  • bacteria: peptidoglycans
  • archaea: polysaccharides
  • provide support. sometimes a secondary wall forms beneath the primary one.
37
Q

Mitochondria

A
  • aerobic respiration
38
Q

Chloroplasts

A
  • photosynthesis, plant process of incorporating energy from sunlight into carbohydrates.
39
Q

Extracellular Matrix

A
  • found in animals
  • area between adjacent cells (beyond plasma membrane and glycocalyx)
  • occupied by fibrous structural proteins, adhesion proteins, and polysaccharides secreted by cells: provide mechanical support and help bind adjacent cells (collagen most common here, also integrin and fibronectin). Laminin can be seen as well
40
Q

Plastids

A
  • double-layer membrane found in plant cells.
  • chloroplasts: site of photosynthesis
  • leucoplasts: specialize in storage or biosynthetic fxns
    a. amyloplasts: starch
    b. elaioplasts: lipid
    c. proteinoplasts: protein
  • chromoplasts: store carotenoids
41
Q

Mitochondria

A
  • make ATP
  • also fatty acid catabolism (B oxidation)
  • have their own circular DNA and ribosomes (endosymbiotic theory)
42
Q

Cytoskeleton

A
  • microtubules: flagella and cilia (largest)
  • intermediate filaments:
  • microfilaments: (smallest)
  • in euk cells, aids in cell division, cell crawling, and movement of cytoplasm and organelles.
43
Q

Endomembrane System

A
  • network of organelles and structures, either directly or indirectly connected that function in transport of proteins and other macromolecules into/out cell
  • plasma membrane, ER, golgi, nuclear envelope, lysosomes, vacuoles, vesicles, endosomes, but not mitochondria or chloroplasts
44
Q

Plant Cells

A
  • in hypotonic solution (normal state) -> vacuole swells -> turgid
  • in isotonic solution -> plant cell flaccid
  • in hypertonic solution -> cell is plasmolyzed; cytoplasm pulled away from cell wall.
  • fungal cells also remain turgid due to cell wall, but animal cell will burst (cytolysis)
45
Q

Intracellular Circulation

A
  • Brownian movement: particles move due to kinetic energy, spreads small suspended particles throughout cytoplasm
  • cyclosis/streaming: circular motion of cytoplasm around cell transport molecules
  • endoplasmic reticulum: provide channel through cytoplasm, provide direct passage from plasma membrane to nuclear membrane
46
Q

Extracellular Circulation

A
  • Diffusion: if cells in close contact w/ external environment can suffice for food and respiration needs. Also used to transport materials between cells and interstitial fluid around cells in more complex animals
  • circulatory system: complex animals we/ cell too far from external environment. use vessels
47
Q

Cell Junctions

A
  • serve to anchor cells to one another or provide passageway for cellular exchange.
  • Anchoring junctions: protein attachments between adjacent animal cells. Ex. Desmosome: consists of proteins (including keratin) that bind adjacent cells together, also associated w/ protein filaments that extend into interior of cell and hold cellular structures together. present in tissues w/ mechanical stress - skin epithelium, cervix/uterus.
  • Tight junctions: tightly stitched seams between animal cells. prevents passage of material between cells. ex. cells lining digestive tract where material must pass through cells (rather than intercellular spaces)
  • Communicating junctions:passageways between cells that allow transfer of chemical or electrical signals. two kinds:
48
Q

Communicating Junctions

A
  • two kinds:
    1. gap junctions: narrow tunnel btw animal cells consissting of proteins called connexins. The proteins prevent mixing of cytoplasm but allow exchange of stuff. Are essentially channel proteins of two adjacent cells. Bec. the proteins of each cell extend beyond plasma membrane before they meet, a small gap occurs between the two plasma membranes. present in tissue like heart for passage of electrical impulses.
    2. Plasmodesmata: narrow channels between plant cells. a narrow tube of endoplasmic reticulum called a desmotubule, surrounded by cytoplasm and plasma membrane passes through the channel. Material exchange occurs through cytoplasm surrounding the desmotubule
49
Q

Differences Between Plant and Animal Cells

A
  • presence of cell walls, chloroplasts, and central vacuoles in plant cells and their absence in animal cells
  • presence of lysosomes, centrioles, and cholesterol in animal cells and their absence in plants.
50
Q

Eukaryotes

A
  • all organisms except bacteria, cyanobacteria, and archaebacteria
51
Q

Prokaryotes

A
  • lack all organelles described.
  • plasma membrane, DNA molecule, ribosomes, cytoplasm, and cell wall.
  • no nucleus
  • single (circular) naked DNA (no chromatin)
  • 50 S + 30 S = 70 S ribosomes
  • cell walls (peptidoglycan); archaea (polysaccharides)
  • flagella constructed from flagellin not microtubules
52
Q

Bulk Flow

A
  • collective movement of substances in same direction in response to a force or pressure. Blood moving through a blood vessel is bulk flow.
53
Q

Passive Transport

A
  • no energy required
    1. simple diffusion: net movement from high conc to low conc
    2. Osmosis: diffusion of H2O across a selectively permeable membrane. Turgor pressure is the osmotic pressure that develops when H2O enters cells of plants and microorganisms.
    3. Dialysis: diffusion of solutes across a selectively permeable membrane. Term usually used when different solutes are separated by a selectively permeable membrane.
    4. Plasmolysis: movement of H2O out of a cell (osmosis) that results in collapse of cell (especially plant cells w/ central vacuoles)
    5. Facilitated Diffusion: diffusion of solutes or H2O through channel proteins in plasma membrane. Water can pass plasma membrane w/out help but aquaporins increase rate by facilitated diffusion.
    6. Countercurrent Exchange: diffusion of substances between two regions in which substances are moving by bulk flow in opposite directions. Ex. direction of flow of H2O through gills of fish is oppostie flow of blood ( diffusion of O2 from H2O is maximized this way)
54
Q

Active Transport

A
  • movement of solutes against gradient
  • require energy (usually ATP)
  • transport proteins in plasma membrane transfer solutes such as small ions (Na+, K+, Cl+, H+), amino acids, and monosaccharides
  • endocytosis and exocytosis
55
Q

Vesicular Transport

A
  • Exocytosis; vesicles fusing w/ plasma membrane and release contents to outside of cells
  • Endocytosis: capture of substances outside the cell when plasma membrane merges to engulf it. three kinds:
    1. Phagocytosis: cellular eating. undissovled materials enter cell. plasma membrane wraps around solid material and engulfs it, forming a phagocytic vesicle. Phagocytic cells (such as WBCs) engulf bacteria in this manner.
    2. Pinocytosis: cellular drinking. when dissolved materials enter the cell. plasma membrane folds inward and encircles the liquid inside a vesicle.
    3. Receptor-mediated endocytosis: a form of pinocytosis when specific molecules in fluid surrounding cell bind receptors in plasma membrane -> membrane pits, receptors and the specific molecules (ligands) fold inward and formation of vesicle folows. ex. proteins that transport cholesterol in blood (low-density lipoproteins) and certain hormones.

DAT Biology (19 decks)

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