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56 Cards in this Set
- Front
- Back
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Increase in size and multicellularity can create problems such as surface area to volume ratio. What prevents the cell from overheating due to this?
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Organelles increase the total surface area, evening out the surface area to volume ratio. i.e. connection between plasma membrane and intracellular membranes such as ER
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Advantages of comparmentalization
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Most or all enzymes of a metabolic pathway concentrated in one location, allows substrates to accumulate in specific comparments, pH, Ions and cofactors, allosteric regulation, storage
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What is an allosteric regulation?
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The process by which a molecule binds to a site on an enzyme other than the active site that changes the enzyme shapes and either acts as an inhibitor or activator. Self limiting. Liken to negative feedback with hormones
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What feature makes a plasma membrane asymmetrical?
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Glycolipids. Only found on the extracellular surface of the membrane.
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What are the two types of membrane models?
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Particulate Model
Lamellar Model |
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What is Particulate membrane model?
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Single layer of globular subunits of proteins and lipids
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What is a lamellar membrane model?
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Sheet-like layers of proteins and lipids. Double layer of lipids between two layers of proteins.
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What factors affect the fluidity of the plasma membrane?
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Cholesterol content, hydration, fatty acid side chain, degrees of saturation, temperature (applies to plasma membrane and organelle membrane)
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What is the most common lipid in the lipid bilayer?
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Phospholipids - consist of phosphotidyl group complexed to structures like choline, serine, etc.
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What factors affect the fatty acid chain of phospholipids?
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Changes in diet (changes length and degree of saturation)
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Why is there cholesterol in membranes?
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Allows fatty acid chains to be more tightly bound inducing reduction in permeability, thickens bilayer prevening crystalization, provides mechanical stability, enhances fluidity
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What are glycolipids mostly derived from?
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Sphingosine - long amino alcohol
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What are the two types of glycolipids?
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Neutral and Complex
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What are Neutral glycolipids?
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Polar head group consists of 1-15 neutral sugars (i.e. galactocerebroside - the main glycolipid in myelin)
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What are complex glycolipids?
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Also known as gangliosides. Contain one or more sialic acid residues (N-acetyl neuraminic acid) w/ net negative charge. Most abundant in neurons constituting 6% total lipid mass.
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What are peripheral (extrinsic) proteins?
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Hydrophilic, relatively easy to isolate, function in cell-cell aggregation
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What are integral (intrinsic) proteins?
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Hydrophobic, hard to isolate. Transport proteins, enzymatic activity, structure, etc.
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What cellular organelle has its own DNA?
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Mitochondria - circular DNA - most genes are transferred into the nucleus
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What cellular organelle produces 95-98% of ATP?
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Mitochondria - the rest of the 2-5% is produced by glycolysis and creatinie phosphate
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What cellular organelle divides independently of the cell?
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Mitochondria
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What are the functions of Mitochondria?
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95-98% of ATP production, apoptosis, large generator of reactive oxygen specs, human genetic disorders - implicated w/ neurodegenerative disease (alzheimers, parkinsons, etc)
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What are the main functions of Smooth Endoplasmic Reticulum?
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Synthesis of steroids, phospholipids and glycolipids, drug detox, hydroxylation, carbohydrate synthesis
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True or false, smooth endoplasmic reticulum can become rough endoplasmic reticulum and vice versa.
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True
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What is the function of ribosomes?
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Formation of proteins from individual amino acids using messenger RNA (Translation)
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Is the golgi apperatus large or small on secretory cells, nerve cells, muscle cells?
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Very large on secretory and nerve cells. Small in muscle cells.
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What are the functions of the golgi apperatus?
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Glycosylation of proteins (i.e. galactotransferases) and secretion of glycoprotiens, remodeling of membranes, synthesis of carbohydrates for glycosylation
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What cells are lysosomes most abundant in?
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Leukocytes, phagocytes, damaged cells, during apoptosis, during phagocytosis
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What is Pompes Disease in relation to lysosomes?
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Glycogen is taken up by lysosomes but not digested.
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What is the Danielli-Davson "sandwich model?"
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Proposed model- phopholipid bilayer lays between two layers of protein
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Drug detoxification using cytochrome p450 which increases drug solubility is carried out in which organelle?
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Smooth Endoplasmic Reticulum
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3 types of diffusion:
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Through lipid bilayer, through protein channel, facilitated diffusion
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What is Fick's Law of Diffusion?
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With concentration gradient. When surface area increases, diffusion increases
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What four factors affect net diffusion?
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Concentration gradient, permeability of membrane, electrical potential difference, pressure difference
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Facilitated Diffusion
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Diffusion (high-low concentration) but used for large particles that are non-lipid soluble and too big for pores
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Properties of Facilitated Diffusion (5)
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Uses carrier molecules, with concentration gradient (no ATP), equilibrium, saturation (limited # carrier molecules), specificity (because of carrier molecule)
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Properties of Active Transport (6)
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Against concentration gradient (using ATP), no equilibrium, carrier molecule, saturation, specificity, primary and secondary types
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Difference between primary and secondary active transport
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Primary: Uses ATP to move a molecule against concentration gradient
Secondary: Uses ion concentration - against concentration gradient, exchange of molecules across each side of membrane |
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Formula for Osmotic pressure
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pi=iRT x (hc-lc)
osmotic pressure = (# of particles time gas constant times temp in Kelvin)(high concentration minus low concentration) |
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Mechanism for phagocytosis & pinocytosis (cell drinking)
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Particle attachment to plasma membrane, influx Na+ depolarize membrane, release Ca+ from ER, Ca+ induced activation of microfilaments and membrane contraction, enclosure of particles, reuptake of Ca+ into E.R., engulfment of particle, fusion of lysosome
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What is the bilayer lipid membrane?
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Primarily phospholipid with cholesterol which provides mechanical stability, enhanced fluidity and prevents hydrocarbon chains from "sticking" together
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What is the function of rough endoplasmic reticulum?
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Protein synthesis post-translation (not a part of translation)
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What is the function of smooth endoplasmic reticulum?
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Drug detoxification, hydroxylation, lipid synthesis, carbohydrate synthesis
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In the particulate model of the plasma membrane it is assumed that the membrane is comprised of what?
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A single layer of globular proteins and lipids
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What shows membrane asymmetry and may function in cellular communication?
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Glycolipids
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Drug detoxification using cytochrome p450 which increases drug solubility is carried out in what organelle?
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Smooth endoplasmic reticulum
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What is the difference between osmolarity and molarity?
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Osmolarity is the number of solutes dissociated. Molarity is the number of solutes (dissociated or associated)
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What are the definitions of isotonic, hypertonic and hypotonic?
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Isotonic: equal flow of water in and out of cell, Hypertonic: higher solute content (in body, an example is the loop of henle), Hypotonic: lower solute content
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What is the normal plasma osmotic pressure?
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300 MosM
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What is osmotic pressure primarily dependent upon?
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Number of particles (size does not matter)
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Which of the following is not a factor that influences the rate of diffusion? A) distance for diffusion, B) Concentration of substance, C) Energy available for transport, D) D.M.W. of diffusing molecule
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C) Energy available for transport
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What are three factors that influence the rate of diffusion?
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Distance for diffusion, concentration of substance, D.M.W. of diffusing molecule
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At a plasma osmotic pressure of 260 MosM, would urine conentration increase, decrease, or remain unaltered?
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Decrease
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What is the formula for diffusion?
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Diffusion is equal to the difference in concentration gradient times surface area times temperature - all over the square root of the molecular weight times distance
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What is the relationship between diffusion rate and membrane permeability?
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Diffusion rate is directly proportional to membrane permeability
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Where are osmoreceptors located?
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Hypothalamus
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What process occurs when plasma osmolarity increases above 300 MosM?
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Cells crenate - Action potential sent to the supraoptic nucleus of the hypothalamus - Causes production of ADH (vasopressin) - Stimulates the collecting ducts to be permeable to water - causes concentrated urine
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