Chapter 4: Membrane Structure and Function
Highlight = Key Term Highlight = Important Concept
● High blood sugar (glucose) levels over a long period
○ Frequent urination increased thirst, higher hunger
● Many long-term health problems
Fluid-mosaic model of plasma membrane
● Selectively permeable
● Maintains homeostasis
● Primarily made of proteins and phospholipids
● Amino acids can be polar or nonpolar
● Protein connected to sugar = glycoprotein
Permeability of membrane
○ Nature-polarity or charge
● Small molecules diffuse through membranes easier
● Charged molecules need channel proteins
What characteristics of glucose (C6H12O6 ) make it unlikely to diffuse across a phospholipid membrane?
● It’s a large polar molecule
● The hydroxyl group makes it polar
How does glucose got to the membrane of an intestine cell?
● Diffusion: why do molecule diffuse?
○ They want to get away from each other
○ They have heat that allows them to move away from each other Don't forget about the age old question of What do the different trophic levels ensure in ecosystem?
○ They have heat that allows them to move away from each other
○ Move down the concentration gradient
Problem with too much glucose
● Osmosis and osmotic pressure
● Isotonic- same amount dissolved inside cell as well as outside the cell ● Hypotonic- less salt in solution than there is around the cell
○ Purified water (very little dissolved in it)
● Plant cell in hypotonic solution
○ Central vacuole fills with water and turgor pressure develops
What would be the physiological response of a human that has too much glucose in their blood?
● Urinate more → pee would be sweet
● Thirst → drink more to try to fix it
Symptoms of diabetes have to do with homeostasis
● Increased urination
● Increased thirst
● Bring back blood
Functions of membrane proteins
● Channel proteins
○ Allow certain molecules through coding for proteins in DNA in nucleus ○ Cystic fibrosis- change in DNA for channel proteins Don't forget about the age old question of What is the contribution of camillo golgi in sensory physiology?
○ Specialized for water
● Carrier Proteins
○ Glucose requires carrier proteins (GLUT) to get through membrane ● Cell Recognition proteins
○ Glycoprotein let your body know it’s you
● Receptor Proteins
○ Get a signal and change things going on in the cell
● Enzymatic Proteins
○ Take a molecule and put it through an enzymatic reaction
● Rise in blood glucose causes pancreas to release insulin
● Insulin travels to different cells throughout the body to induce them to take up glucose
Which type of membrane protein will insulin interact with?
● Receptor Proteins
○ Hormone that sends signal to receptor
When insulin producing cells are attacked by someone’s own immune system. What type of membrane protein is probably involved?
Cell recognition We also discuss several other topics like How much amount of energy is produced by fats in vegetable oil?
Some people are insulin sensitive. What could cause this?
● Receptor protein not working
● Carry mutation that makes receptor protein not work
● GLUT 4 that doesn’t work (carrier protein)
Transport across membranes
● Transport by carrier proteins
● Combine with a molecule or ion to be transported across the membrane
● Small molecules that are not lipid soluble
● Molecules follow the concentration gradient
● Energy is not required and is reversible
● Molecules or ions combine with carrier proteins
○ Often called pumps
● Molecules move against the concentration gradient
○ Entering or leaving cell
○ Accumulate either inside or outside the cell We also discuss several other topics like What is the contemporary psychodynamic theory?
● Energy and carrier proteins are required
○ Usually by ATP
1. Carrier has a shape that allows it to take up 3 Na+
2. ATP is split
3. Change in shape results and causes carrier to release 3 Na out of the cell 4. Carrier has a shape that allows it to take up 2K+
5. Phosphate group is released from carrier We also discuss several other topics like What three beliefs were christians supposed to accept about god’s nature and the existence of evil?
Don't forget about the age old question of In geology, what is seismology?
6. Change in shape results and causes carrier to release 2K+ inside the cell
● A vesicle fuses with the plasma membrane as secretion occurs
● Cells take in substances by vesicle formation
● Phagocytosis: the material taken in is large, such as food particle or another cell.
● Pinocytosis: occurs when vesicles from around a liquid or around very small particles
○ Receptor mediated endocytosis: uses a receptor protein shaped so that a specific molecules, such as a vitamin, peptide hormone, or lipoprotein, can bind to it.