Unit 2: Cells, Membranes and Signaling … CELL MEMBRANE. Chapter 5 Hillis Textbook. HOW DOES THE LAB RELATE TO THE NEXT CHAPTER?. SURFACE AREA: the entire outer covering of a cell that enables materials pass. VOLUME: the inside spare that can be filled with organelles/etc .
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SURFACE AREA: the entire outer covering of a cell that enables materials pass.
VOLUME: the inside spare that can be filled with organelles/etc.
CELLS WITH MORE SURFACE AREA AND LESS VOLUME WILL BE VERY EFFICIENT!!!
You looked at the rate of diffusion
Which cell could diffuse materials quicker and more efficiently?
These molecules get in and out of the cell by the CELL MEMBRANE!
A membrane’s structure and functions are determined by its constituents: lipids, proteins, and carbohydrates.
The general structure of membranes is known as the fluid mosaic model.
Phospholipids form a bilayer which is like a “lake” in which a variety of proteins “float.”
Lipids form the hydrophobic core of the membrane.
Most lipid molecules are phospholipids with two regions:
electrically charged “heads”
that associate with water
nonpolar fatty acid “tails” that
do not dissolve in water
A bilayer is formed when the fatty acid “tails” associate with each other and the polar “heads” face the aqueous environment (Water).
Bilayer organization helps membranes fuse during vesicle formation and phagocytosis.
Membranes are fluid due to the flexible composition and mosaic due to the patterns that form from lipids and proteins
Two important factors in membrane fluidity:
Lipid composition—types of fatty acids can increase or decrease fluidity
Temperature—membrane fluidity decreases in colder conditions
Proteins are randomly scattered within the cell membrane to form a mosaic pattern
Biological membranes contain proteins, with varying ratios of phospholipids.
Peripheral membrane proteins lack hydrophobic groups and are not embedded in the bilayer.
Integral membrane proteins are partly embedded in the phospholipid bilayer.
Anchored membrane proteins have lipid components that anchor them in the bilayer.
Proteins are asymmetrically distributed on the inner and outer membrane surfaces.
A transmembrane protein extends through the bilayer on both sides, and may have different functions in its external and transmembrane domains.
Some membrane proteins can move within the phosopholipid bilayer, while others are restricted.
Proteins inside the cell can restrict movement of membrane proteins, as can attachments to the cytoskeleton.
Plasma membrane carbohydrates are located on the outer membrane and can serve as recognition sites.
Glycolipid—a carbohydrate bonded to a lipid
Glycoprotein—a carbohydrate bonded to a protein
Biological membranes allow some substances, and not others, to pass. This is known as selective permeability.
Two processes of transport:
Passive transport does not require metabolic energy.
Active transport requires input of metabolic energy.