Cell Bio Exam 2

Types of transport: passive

)Passive: movement from area of high to low, no energy required Simple: when small, NONPOLAR, molecules can simply diffuse through the membrane without disruption or any help. ex: Oxygen Osmosis: diffusion of water Facilitated: has a doorway through the membrane to allow for molecules to go through without disturbing layer. Ex: ion channel. (Carbonyls displace water and still satisfy partial charge in the selectivity filter(no room for water anymore). If ion was smaller: distance between ion and carbonyl interaction would not occur, distorts E profile and is UNFAVORABLE Structure: 4 subunits with a pore center that have selective passing of K+ ions)

Why does a membrane need doorways?

- Absorb nutrients - Export waste - Access their chemical environment - Maintain correct pH - Control electrical potential across membrane

How thick is the plasma membrane?

50 atoms

Cell polarity

Apical: faces gut contents; transport proteins involved in the uptake of nutrients from the gut are confined to apical surface Basal: export of solutes out of the epithelial cell into the tissues and bloodstream are confined to the basal surfaces; lateral

Lysosome, acidification, autophagy, autophagosome

Lysosome: pH of 5, 50 digestive enzymes that inhabit it. Acts as acid VAT to dispose of things Acidification: if a large solid/liquid comes in, it acidifies and breaks down the contents so that no danger inside of them can replicate/spread. OR if cell surface is worn out in a protein/lipid it can be recycled - Endosomes acidify and become lysosomes Autophagy: cell packages and digests some of its OWN contents Autophagosome: when vesicles fuse and make double membrane compartment and surround material it wants to digest; this gets acidified and becomes lysosome

Eukaryotic membrane

Plamsa mem: only 2% of total membrane 98% of membrane is inside Bulk of membrane: ER and mitochondria

Asymmetric bilayer

Reason for asymmetry: outer leaflet is exposed to outside of the cell whereas the inner leaflet is exposed to cytoplasm. Different environments require different conditions.

Lipid bilayer, leaflets

The lipid bilayer is a thin polar membrane made of two layers of lipid molecules. contains 2 types of leaflets -inner leaflet: phospholipids face inside of cell/cytoplasm - outer leaflet: phospholipids that face outside of cell/extracellular fluid

In a patch of animal cell membrane about 10 μm in area, which will be true?

There will be more lipids than proteins.

Why do phospholipids aggregate to form cell membranes?

They are amphipathic.

What happens to proteins with no signal sequence that are made in the cytosol?

They remain in the cytosol.

Which membrane would show a more rapid recovery of fluorescence in a FRAP study?

a membrane containing a larger proportion of unsaturated fatty acids

What types of molecules might these researchers consider to be the original building blocks of cell membranes?

amphipathic molecules

How do the interiors of the ER, Golgi apparatus, endosomes, and lysosomes communicate with each other?

by small vesicles that bud off of one organelle and fuse with another

Most mitochondrial and chloroplast proteins are made within which part of the cell?

cytosol

In the α helices of transmembrane proteins, the hydrophobic side chains face which direction?

the outside of the membrane-spanning helix

Through which of the following do proteins travel from one cisterna to the next in the Golgi apparatus?

transport vesicles that bud from one cisterna and fuse with the next

How is transport regulated

transportation of each type of molecule is under control of a different transmembrane protein. Ex: nucleotide, sugar, AA, Na+

In a lipid bilayer, where do lipids rapidly diffuse?

within the plane of their own monolayer. The lipid bilayer is a two-dimensional fluid in which phospholipids rapidly diffuse within the plane of their own monolayer.

exocytosis and endocytosis

exo = getting stuff out. ex: secretion endo = taking stuff in. ex: clathrin (protein that has 3 legs which are trimers) clathrin cage: each triskelia can assemble by interaction with other copies of itself to create chicken wire pattern Steps: Triskelia in cytosol and indirectly interact with membrane proteins through adapter protein 2. Assemble cage like fashion w/ curvature and other proteins pinch it off (E needed) 3. Coated pit to coated vesicle to coat disassembles and individual triskelia release and fly away as uncoated vesicles that can now fuse

On what side of the plasma membrane are the carbohydrate chains of glycoproteins, proteoglycans, and glycolipids located?

extracellular (facing outside)

Compartments

extracellular: complex network of polysaccharides and proteins secreted by cells Cytosolic: monolayer that always faces the cytosol Lumen: interior space of an organelle

What is the end of a phospholipid tail described as?

hydrophobic

Ionic and nonionic detergents

ionic: strong detergents, go in and disrupt the membrane creating a bridge between water and the hydrophobic side; destroys cell in process. Ex: SDS nonionic: weak detergents; they do not destroy cell, but instead poke holes in the membrane to preserve cells and proteins. Ex: triton

Glycosylation/glycoprotein

lation- process of adding sugar chains to a compound protein- modified proteins in which sugar chains are added to the protein (make up carbohydrate layer)

Cisternae

membrane disks (flat) with fluid -transport vesicles and deliver proteins through stacks but resident enzyme also moves forward, move through sacks over time

Golgi apparatus

modification, sorting, packaging of proteins/lipids for other secretion or delivery

concentration gradient

movement from high to low is WITH gradient, while low to high is AGAINT, thus causing disruptions in the bilayer

How do proteins associate with membranes, peripheral, lipid modification, gpi

peripheral: no part of the protein is inserted in the membrane, loosely attached to integrals. function as enzymes, motor proteins, cell-to-cell connections GPI Anchor: extracellular, phospholipid with sugar linkage to protein of interest and the protein is stapled onto phospholipid head groups Attached to integral protein: protein-protein interaction with transmembrane protein; partners with transmembrane single/multi pass

Phagocytosis, phagosome, pinocytosis

phagocytosis: cell eating, just below plasma membrane phagosome: large vesicles that contain microorganisms and cell debris (will fuse w lysosomes where food particles are digested) Pino: cell drinking (what was outside is not getting mixed into cytosol-still in vesicles)

Secreted protein/signal sequence (signal peptide)/nascent protein

polypeptide, when off the ribosome is assessed to detemine whether it has a hydrophobic string of AA at the N-terminus. If yes, it is recognized and brought to the ER and puts into translocation channel which is threaded to lumen

Cell cortex/ membrane cytoskeleton

special layer of cytoplasm that is located on the inner face of the plasma membrane. In an animal cell, it will be rich in actin filaments that help conduct the shape of the cell and drive cell movement. Ex: red blood cells have a protein, spectrin that forms a lattice that provides support

Endoplasmic reticulum

synthesis of most lipids and most proteins for distribution to many organelles. Consists of a series of parallel interconnected membranous tubes that enclose fluid-filled interiors. Rough- ribosomes Smooth- No ribosomes

Which cellular compartment acts as the main sorting station for extracellular cargo molecules taken up by endocytosis?

Endosomes

How do proteins associate with membranes, integral, passes

- increase the density of proteins in membranes (about 50 lipids per protein) - Integral: in membranem across the bilayer with some of the protein in the cell, some out of cell, and other spanning across the membrane. Function as enzymes, transport proteins, or receptors Single pass: aplha helices Multiple pass: beta barrel or multiple alpha helices (3 or more alpha helices pass thru membrane)

Which statements are true about the differences between phospholipids and detergents?

-Phospholipids have two hydrocarbon tails, whereas detergents have just one. -Detergents are shaped like cones, whereas phospholipids are more cylindrical. -Phospholipids form bilayers in water, whereas detergents tend to form micelles.

Plasma membrane

-surrounds cell; maintains different conditions inside vs. out - Home to proteins, 2% of cells total membrane - Eukaryotes, most of membrane is intracellular -ER: 50%, mitochondria: 30%

Clathrin Cage

Clathrin is responsible for shaping the forming vesicle during endocytosis. If clathrin forms an open-ended lattice, the vesicle will not properly form and endocytosis will be inhibited.

Proteins destined for the Golgi apparatus, endosomes, lysosomes, and even the cell surface must pass through which organelle?

ER

The outer membrane of the nucleus is continuous with the membrane of which other organelle?

ER

Which organelle is important for controlling the concentration of calcium ions in the cytosol?

ER

Why do phospholipids form bilayers in water?

The hydrophilic head is attracted to water while the hydrophobic tail shuns water.

Protein translocation

The signal peptide is recognized by an enzyme that clips off the N terminus so that it can survive in the lumen conditions If in mem: needs to be 2nd string of hydrophobic AA that causes it to be released in the membrane with part being out of the cytosol and other part being in lumen Glycosylation: adding a sugar onto a molecule

Which of these strategies do prokaryotic cells use to isolate and organize their chemical reactions?

aggregating proteins into multicomponent complexes that form biochemical subcompartments with distinct functions

What is the whole phospholipid molecule described as?

amphipathic

Lateral mobility:

can move: lateral diffusion for some, can have flexion, and can have rotation cannot: no flip flop, this is rare and must be catalyzed by a protein, it will not happen by chance

The shape of a cell and the mechanical properties of its plasma membrane are determined by a meshwork of fibrous proteins called what?

cell cortex

membrane permeability

degree to which a membrane allows a substance to pass through it

Early/late endosome

early: just beneath the plasma membrane; where material is brought in from cell surface and processes late: located closer to nucleus

The movement of materials from the plasma membrane, through endosomes, and then to lysosomes describes which type of pathway?

endocytic pathway

2D fluid

flat structure, can extend in either direction maintaining same thickness (thin). The fluid isn't stuck together, but simply loosely amongst molecules

Hydropathy plots

highlights areas that have many hydrophobic side chains. Unfolds the protein so only primary sequence is seen, and then analyzes the amino acids -X-axis: amino acid number (based on hydrophobicity/hydrophilicity -Hydrophobic: top of graph - Hydrophilic: bottom of graph -Y-axis: the hydropathy index that represents # of hydrophilic or hydrophobic side chains

Porin proteins—which form large, water-filled pores in mitochondrial and bacterial outer membranes—fold into β-barrel structures. The amino acids that face the outside of the barrel have what kind of side chains?

hydrophobic

In a typical human secretory cell, which of the following membranes has the largest surface area?

rough ER

Types of transport: active

shipping molecules across a membrane, often against concentration gradient, requiring energy and is usually as a coupled ion gradient Pumps: burning of ATP allows for confirmation change which drives some ions out. Ex: sodium potassium pump-1/3 of atp made by cells is spent to power sodium potassium pump, for each ATP broken down, it moves 3Na+ out and 2K+ inside the cell (similar to a trade) Contransporters: transports materials against the gradient, has moving parts that change the confirmation. Indirectly uses ATP. Ex: glycine transporter: high concentration of sodium on outside 3 Na for 1 glycine. Symporter: moves 2 molecules in the same direction Endocytosis/exocytosis: endo: within exo:out

Protein sorting

similar to post office; once packaged, it is sent off in vesicles to fuse with PM dumping lumen components to outside of cell