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Questions and Answers
What percentage of proteins in the plasma membrane are integral/intrinsic proteins?
What type of transport requires energy and moves substances against the concentration gradient?
Which type of protein movement was confirmed by the 1972 Singer & Nicolson model for the plasma membrane?
What is the main example of a channel protein involved in facilitated diffusion?
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What is the role of glycoproteins on the cell surface?
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Study Notes
Protein Classification
- Peripheral proteins make up 10% of membrane proteins, while integral proteins make up 90%
- Integral proteins are transmembrane or in-wall, meaning they span across the membrane or are embedded in it
Transport Mechanisms
Passive Transport
- Occurs along the concentration gradient, requiring no energy
- Examples include passive diffusion, where molecules move from an area of higher concentration to an area of lower concentration
Facilitated Diffusion
- Involves the use of channel proteins or carrier proteins to facilitate transport
- Channel proteins form a pore or channel in the membrane, allowing specific molecules to pass through
- Examples include porin proteins
Active Transport
- Transport occurs against the concentration gradient, requiring energy consumption
- Examples include the Na+ pump, which transports sodium ions into the cell against their concentration gradient
Osmosis
- Movement of water molecules from an area of higher concentration to an area of lower concentration
- Occurs through a selectively permeable membrane, allowing polar molecules like water to pass through
Plasma Membrane
- Discovered by Singer and Nicolson in 1972
- Labeling proteins on the membrane surface confirms the fluid mosaic model, where proteins are able to move laterally but do not flip-flop across the membrane
Glycoproteins and Cell Recognition
- Glycoproteins, or sugar-proteins, are important for cell-to-cell recognition
- They provide mobility and flexibility to the cell surface, allowing for interactions with other cells
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Description
This quiz covers the types of proteins and their roles in cell membrane transport, including peripheral and integral proteins, passive and active transport, facilitated diffusion, and osmosis.
