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Biol 1103 Chapter 5-8 Notes

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Detailed and comprehensive notes Chapter 5-8. *Essential Study Material!!

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  • October 3, 2024
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  • 2021/2022
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Chapters 5-8 study guides

Chapter 5 Membrane Structure, Synthesis, and Transport
 5.1 Membrane Structure.
 Describe the Fluid-Mosaic Model of Membrane Structure.
o Phospholipid Bilayer Components
 Cell membrane is a fundamental and defining feature of cells, with the
hydrophilic phosphate head groups facing the aqueous environment on
the other side and the hydrophobic tails in the middle.
 Amphipathic
 Phospholipid molecules
 Hydrophobic
 (Water fearing) regions face in
 Hydrophilic
 (Water loving) regions face out
o Fluid-Mosaic Model
 Mosaic of phospholipid, protein, and carbohydrate molecules
 Fluid lipids and proteins move more relative to each other within
membrane
 Two leaflets (halves of bilayer) asymmetrical
 Identify the Three Different Types of Membrane Proteins.
o Transmembrane Proteins
 Physically embedded in hydrophobic region of phospholipid bilayer
 Integral membrane protein
o Lipid-Anchored Protein
 Covalent attachment of lipid to amino acid within protein
 Integral membrane protein
o Peripheral Protein
 Non-covalently bound to
 Integral membrane protein
 Polar head groups of phospholipids
 5.2 Fluidity Of Membranes.
 Describe the Fluidity of Membranes.
o Semi-Fluid
 Movement occurs in two directions
 Lipids rotate
 Phospholipids
 Cholesterol
 Proteins move
 Typical phospholipid exchanges places with its neighbor 10 ^7 s^-1
 CoreSKILL-> Predict How Changes in Lipid Composition Affect Membrane Fluidity.
o Lipid Composition Affects Fluidity by…
 Length of phospholipid tails
 Short = more fluid
 Number of double bonds
 More = more fluid
 Unsaturated
 Cholesterol for stabilization
 Warm temp. – makes more rigid
 Cold temp. - makes more fluid

,  Proteins may be anchored
 5.3 Synthesis Of Membrane Components In Eukaryotic Cells.
 Outline the Synthesis of Lipids at the ER Membrane.
o 1
 In the cytosol, fatty acids are activated by the attachment of a CoA
molecule
o 2
 The fatty acids bond to glycerol-phosphate and are inserted into the
cytosol Inc. leaflet of the ER membrane via acyl transferase
o 3
 The phosphate is removed by a phosphate enzyme.
o 4
 A choline already linked to the phosphate its attached via choline
phosphatransferase.
o 5
 Flippases transfer some of the phospholipids to the other leaflet
 Explain How Transmembrane Proteins are Inserted into the ER Membrane.
o 1
 A protein begins synthesis into the ER, and the ER signal sequence is
cleaved.
o 2
 Polypeptide synthesis continues, a hydrophobic transmembrane
segment is made as the polypeptide is being threaded through the
channel
o 3
 Polypeptide synthesis is completed and the transmembrane sequence
remains in the membrane
 Describe the Process of Glycosylation and its Functional Consequences.
o Glycosylation
 Process of covalently attaching a carbohydrate to a protein or lipid
 Glycolipid
 Carbohydrate to lipid
 Glycoprotein
 Carbohydrate to protein
 N-Linked Glycosylation
 Attachment of carbohydrate to nitrogen atom of asparagine side
chain
 O-Linked Glycosylation
 Addition of sugars to oxygen atom of serine or threonine side chains
 Only in Golgi
o Process of Glycosylation
 1
 Prior to Glycosylation of a polypeptide, a group of 14 sugars is built
onto a lipid in the ER membrane
 2
 Oligosaccaride transferase moves the carbohydrate tree from the
lipid and transfers it to an asparagine in the polypeptide
 3
 Polypeptide synthesis is completed
 5.4 Overview of Membrane Transport.

,  Compare and Contrast Simple Diffusion , Facilitated Diffusion , Passive
Transport , And Active Transport.
o Passive Transport
 Does not require energy
 Solutes moves down or with [] gradient
 Movement of bio chemicals and other atomic or molecular substances
across cell membrane via specific transmembrane integral proteins
 Simple Diffusion
 Diffusion of a solute through membrane without transport
protein
 Substance moves from area of [high] to [low]
 No energy required
 Facilitated Diffusion
 Movement of biochemical and other atomic or molecular
substances across cell membranes without the need of energy
input
 Substance moves from area of [high] to [low]
o Active Transport
 Requires energy to move substances across cell membranes
 Substance moves from area of [low] to [high]
o Selectively Permeable
 When a cell lets some things across the cell membrane but excludes
others
o Membrane Transport
 The movement of particles of any substance so that they spread out
evenly into the available space
o Transmembrane Gradient
 Protein channels and carrier proteins
 Concentration Gradient
 Amount of gradient difference in concentration from one area to
another
o Electrochemical Gradient
 Usually for an ion that can move across a membrane
 Describe the Process of Osmosis and how it Affects Cell Structure.
o Osmosis
 Diffusion of water
 Moves water from a higher concentration to a lower concentration
o Isotonic
 Solute concentration outside equals the inside, no net movement,
animals like this
 _[solute]=[solute] on either side of the membrane
o Hypertonic
 Solute concentration is greater outside then inside
 Cell shrinks or shrivels
 Water becomes plasmolyze
 3.5% solute
o Hypotonic
 Solute concentration is greater inside than outside
 Water enters the cell and it gets larger
 Plants like this and animals don’t because they’ll explode
 0.1% solute

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