New User Special Price Expires in

Let's log you in.

Sign in with Facebook


Don't have a StudySoup account? Create one here!


Create a StudySoup account

Be part of our community, it's free to join!

Sign up with Facebook


Create your account
By creating an account you agree to StudySoup's terms and conditions and privacy policy

Already have a StudySoup account? Login here

Chapter 7 Cell Membrane

by: Sophia Notetaker

Chapter 7 Cell Membrane BIOC 0170

Marketplace > University of Pittsburgh > Biology > BIOC 0170 > Chapter 7 Cell Membrane
Sophia Notetaker
GPA 3.5
View Full Document for 0 Karma

View Full Document


Unlock These Notes for FREE

Enter your email below and we will instantly email you these Notes for Foundation of Biology I

(Limited time offer)

Unlock Notes

Already have a StudySoup account? Login here

Unlock FREE Class Notes

Enter your email below to receive Foundation of Biology I notes

Everyone needs better class notes. Enter your email and we will send you notes for this class for free.

Unlock FREE notes

About this Document

Chapter 7 Cell Membrane
Foundation of Biology I
Barbara Barnhart
Class Notes
chapter 7, cell membrane, Biology




Popular in Foundation of Biology I

Popular in Biology

This 10 page Class Notes was uploaded by Sophia Notetaker on Tuesday February 2, 2016. The Class Notes belongs to BIOC 0170 at University of Pittsburgh taught by Barbara Barnhart in Spring 2016. Since its upload, it has received 22 views. For similar materials see Foundation of Biology I in Biology at University of Pittsburgh.


Reviews for Chapter 7 Cell Membrane


Report this Material


What is Karma?


Karma is the currency of StudySoup.

You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!

Date Created: 02/02/16
Chapter 7 – Membranes I. Membrane Structure and Synthesis a. Examples of Cellular membranes: i. Plasma, ER, Golgi, Vesicles ii. Structures – Membranes made up of 1. Lipids 2. Proteins 3. Carbohydrates Green – carbs. Purple dark bubble – proteins. b. Membrane Lipids i. Phospholipid bilayer (main component) 1. Hydrophilic head 2. Hydrophobic tail 3. Amphipathic ii. Fluid Mosaic Model 1. The membrane is a fluid structure with a mosaic of various proteins embedded in or attached to a double layer of phospholipids 2. Freeze Fracture – made model apparent in 1970s 1 Ch. 7 a. Freeze cell, chisel with a knife fracture along hydrophobic region, proteins stay with one side or the other iii. Fluidity 1. lateral drifting; phospholipids can switch places a. Side to side (constant – very fast) b. Flip-Flop (-1 time per month) i. Rare since have to cross hydrophilic head would have to cross hydrophobic tail region 2. Affected by tails a) Unsaturated – Kinked due to double bonds – it is those kinks that made it fluid and flexible – olive oil b) Saturated – Straight due to single bonds; packed closely together, this make it more solid – less fluid – more hydrogen - butter 2 Ch. 7 2. Affected by cholesterol a. wedge between phospholipids b. Cholesterol helps membrane resist changes in fluidity as temp changes – like a buffer i. body temperature 1. Makes membrane more solid/less fluid by holding phospholipids in place ii. Cholesterol lowers temperature needed for solidification – prevents phospholipids from packing too close – keep membrane more fluid and not frozen 3. Membrane Proteins (Mosaic part – both structure and function) a. Just like phospholipids, proteins can move side to side however it is slower than phospholipids b. Mosaic part – membrane is a collage of different proteins c. Proteins determine most of the membranes functions d. Integral Proteins i. Transmembrane ii. Have contract with the hydrophobic region iii. Have cytoplasmic and extracellular portions iv. integrin’s e. Peripheral Proteins i. Not embedded ii. No contact with the hydrophobic region iii. Loosely bound to surface of the membrane 3 Ch. 7 c. Functions of Membrane Proteins i. Transport of Molecules across membrane through the proteins ii. Enzymes – catalyze reactions iii. Signal Transduction – extracellular portion received signal from outside environment and sends message into cell iv. Cell – Cell recognition 1. So cells can recognize each other through complementary proteins v. Intercellular joining 1. Gap junctions, tight junctions, binding of adjacent cells vi. Anchors for cytoskeleton inside cell 4. Membrane Carbohydrates - Some membrane proteins have carbohydrates attached to the extracellular surface of of the plasma membrane a. Needed for cell-cell recognition -Sorting of cells into tissues and organs -rejection of foreign cells by immune system b. Structure -Short, branched chains -attached to proteins (glycoproteins) or lipids (glycolipids) 4 Ch. 7 Membrane Synthesis 1. ER Makes proteins and carbohydrates inside then break off in transport vesicle 2. Transport vesicles fuses with Golgi which process by addition of functional groups 3. Breaks off Golgi as vesicle then fuses to plasma membrane 4. expels it contents a. Everything is coming outside II. Movement of Molecules through Membranes a. Permeability i. Small hydrophobic (nonpolar) molecules can move through membrane ii. Do not need the aid of membrane proteins iii. Hydrophobic would need a protein to aid it to go the hydrophilic tails iv. Hydrophilic molecules can’t get through the hydrophobic tails 1. Need transport proteins b. Types of Transport a. Passive – no energy expended to move molecules across membranes i. Diffusion – tendency of molecules to spread out evenly into available space ii. In absence of other forces (pressure plays a role), a substance will spontaneously diffuse from an area of high concentration to an area of low concentration 1. Concentration gradient 2. Ex. I2KI diffuses in to the starch bag. Because the i2KI has higher concentration iii. Osmosis – diffusion of water across a membrane 1. In living cells the environment, they are in affects the movement of water across the membrane 2. Tonicity – The ability of a surround solution to cause a cell to gain or lose water; partly depends on the concentration of solutes that can not cross the membrane 5 Ch. 7 3. Environments a) Hypotonic – low solute concentration outside of cell but 1. Solution has more water and less particles, 2. Cell has more particles and less water 3. Animal – Lysis – burst, Plant – Turgid high inside the cell, therefore water moves in. b) Hypertonic – high solute concentration outside of cell but low inside the cell, therefore water moves out. - cell has more water less particles -solution has less water and more particles -Water leaves the cell and cell shrinks When it shrinks Animal – Crenation Plant - Plasmolysis c) Isotonic – equilibrium, solute concentration is the same of both sides of the membrane. b. Facilitated Diffusion i. Passage of molecules or ions down their electrochemical gradient across a membrane with the assistance of specific transmembrane transport protein (No energy is need to transport) ii. Polar molecules and ions can not diffuse the phospholipid layer; they are hydrophilic – they need transport proteins to shield them from the hydrophobic tail 1. High to low concentration 2. We need energy when going from low to high iii. Two Types of Transport Proteins 1. Channel Protein – hydrophilic tunnel a. Is going to let the solution go through b. Example: Aquaporin make water moves through c. For ion called ion channels 6 Ch. 7 a) Gates – open and close in response to stimulus 2. Carrier Proteins a. Undergoes subtle change in shape when substance to be transported binds and then released C. Active Transport – requires energy to pump molecules opposite of the concentration gradient 1. Energy source – ATP (Adenosine triphosphate) a. Transfer phosphate group to transporter proteins to provide energy b. Phosphorylation – losing the phosphate i. Translating the phosphate group c. Transport proteins are carrier proteins d. Example – Sodium – Potassium Pump (carrier protein used) 7 Ch. 7 2. Passive vs. Active D. Membrane Potentials 1. The difference in electrical charge (voltage) across a cell’s plasma membrane due to the differential distribution of ions. 2. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances 3. Voltage across a membrane a. Inside more negativity charges than outside therefore its more positively charged ion drawn into cell and negative charge ions go out b. Therefore, concentrated dependent transport (chemical) and membrane (potential) electrical = an electrochemical gradient 4. Electrogenic pumps a. Transport proteins that generates voltage across a membrane b. Pumps store the energy to drive cellular work 8 Ch. 7 c. Important uses: ATP synthesis and cotransport Examples: Proton Pump showing co-transport (sucrose – H+ transporter) E. co-transport 1. a molecule that has been pumped against its concentration gradient will spontaneously move back (diffuse) to the lower concentration side 2. Spontaneous movement of the molecules provides energy to actively transport another molecules 3. Real life applications a. Gatorade replenishes electrolytes. Drink too much Gatorade, and water absorbs and becomes dehydrates F. Large Molecule Transport – requires energy 1. Molecules that are too large to pass through the membrane and do not fit into protein transporters 2. Exocytosis a. Fusion of transport vesicles with plasma membrane b. Contents are secreted c. Exo – Giving it out 3. Endocytosis a. Small area of plasma membrane sinks IN the engulfs stuff outside of membrane, pinches in and breaks away from plasma membrane b. Endo – absorbing and taking in 9 Ch. 7 G. Three Types of Endocytosis 1. Phagocytosis a. “food” intake, plasma membrane sends out little arms and surround food particles i. Vesicle fuses with a lysosome for digestion 2. Pinocytosis a. “Fluid” intake, engulfs fluid to bring in smaller solutes 3. Receptor mediated endocytosis a. “Specific” intake b. Grans specific molecules that are not very concentrated in extracellular environment c. Ligand i. Membrane proteins with specific recognition sites (binds to ligands) that are located on outside of membrane ii. On inside (cytosol) are coat protein iii. Pinches off from plasma membrane and releases molecule into cell iv. Receptor proteins are then recycled and send back out to plasma membrane 10 Ch. 7


Buy Material

Are you sure you want to buy this material for

0 Karma

Buy Material

BOOM! Enjoy Your Free Notes!

We've added these Notes to your profile, click here to view them now.


You're already Subscribed!

Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'

Why people love StudySoup

Jim McGreen Ohio University

"Knowing I can count on the Elite Notetaker in my class allows me to focus on what the professor is saying instead of just scribbling notes the whole time and falling behind."

Allison Fischer University of Alabama

"I signed up to be an Elite Notetaker with 2 of my sorority sisters this semester. We just posted our notes weekly and were each making over $600 per month. I LOVE StudySoup!"

Bentley McCaw University of Florida

"I was shooting for a perfect 4.0 GPA this semester. Having StudySoup as a study aid was critical to helping me achieve my goal...and I nailed it!"


"Their 'Elite Notetakers' are making over $1,200/month in sales by creating high quality content that helps their classmates in a time of need."

Become an Elite Notetaker and start selling your notes online!

Refund Policy


All subscriptions to StudySoup are paid in full at the time of subscribing. To change your credit card information or to cancel your subscription, go to "Edit Settings". All credit card information will be available there. If you should decide to cancel your subscription, it will continue to be valid until the next payment period, as all payments for the current period were made in advance. For special circumstances, please email


StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here:

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.