Download - Plasma Membrane
![Page 1: Plasma Membrane](https://reader036.vdocuments.site/reader036/viewer/2022072116/56812bd0550346895d902e03/html5/thumbnails/1.jpg)
Plasma Membrane
![Page 2: Plasma Membrane](https://reader036.vdocuments.site/reader036/viewer/2022072116/56812bd0550346895d902e03/html5/thumbnails/2.jpg)
Pre-Assessment
1. Which of the following statements concerning membrane proteins is incorrect?
A. They can act as a channel, allowing the transport of ions across the membrane.
B. They often require ATP to actively transport materials across the membrane against a concentration gradient.
C. They may be receptor proteins that bind specific molecules from the surrounding solution, which triggers endocytosis (i.e., receptor-mediated endocytosis).
D. They are usually not particular about what types of chemicals they will allow to cross the membrane.
![Page 3: Plasma Membrane](https://reader036.vdocuments.site/reader036/viewer/2022072116/56812bd0550346895d902e03/html5/thumbnails/3.jpg)
2. Which molecule works to keep the membrane at optimal fluidity?
3. Which molecule is both hydrophobic and hydrophilic and aggregates as a bilayer to form the "fabric" of the membrane?
4. Which molecule may function in facilitated diffusion? 5. Which molecule might serve as a binding site for a
hormone, thereby eliciting a response in the cell?
![Page 4: Plasma Membrane](https://reader036.vdocuments.site/reader036/viewer/2022072116/56812bd0550346895d902e03/html5/thumbnails/4.jpg)
Phospholipid Bilayer• Composed of fatty acid
tails connected to glycerol heads
• non-polar (hydrophobic) fatty acid interior impedes passage of water-soluble substances (it is liquid like a soap bubble)
• Polar heads (hydrophilic) are water soluble
![Page 5: Plasma Membrane](https://reader036.vdocuments.site/reader036/viewer/2022072116/56812bd0550346895d902e03/html5/thumbnails/5.jpg)
Components of a Plasma Membrane
• Phospholipids• Proteins– Integral proteins – completely penetrate the lipid bilayer;
they control the entry and removal of specific molecules– Peripheral proteins – bound to the exterior surface of
the membrane; they have various functions
![Page 6: Plasma Membrane](https://reader036.vdocuments.site/reader036/viewer/2022072116/56812bd0550346895d902e03/html5/thumbnails/6.jpg)
Components of a Plasma Membrane
• Cholesterol– Inside near the fatty acid tails; helps to regulate
membrane fluidity and is important for membrane stability
![Page 7: Plasma Membrane](https://reader036.vdocuments.site/reader036/viewer/2022072116/56812bd0550346895d902e03/html5/thumbnails/7.jpg)
Fluid Mosaic Model
![Page 8: Plasma Membrane](https://reader036.vdocuments.site/reader036/viewer/2022072116/56812bd0550346895d902e03/html5/thumbnails/8.jpg)
The 6 Membrane Protein Functions
1. Hormone binding sites – these proteins have specific shapes exposed to the exterior that fit the shape of specific hormones
2. Enzymes – catalyze chemical reactions; may be on interior or exterior of the cell membrane; often grouped together for a chain reaction (called metabolic pathway)
3. Cell adhesion – proteins hook together to provide temporary or permanent connections; these connections referred to as junctions
![Page 9: Plasma Membrane](https://reader036.vdocuments.site/reader036/viewer/2022072116/56812bd0550346895d902e03/html5/thumbnails/9.jpg)
4. Cell-to-cell communication – many include carbohydrates attached to protein molecules on outside of cell; they provide an ID tag letting other cells know what type of cell they are
5. Channels for passive transport – integral proteins that have a channel in them to allow substances to move through; passive means substances move through from high to low concentration
6. Pumps for active transport – integral proteins that shuttle a substance from one side to the other by changing their shape; this process requires energy in the form of ATP