12 Questions
What is the main function of the phospholipid bilayer in the cell membrane?
The main function of the phospholipid bilayer is to regulate what enters and leaves the cell, maintain cell shape, and provide mechanical support.
What is the difference between hydrophilic and hydrophobic regions of the phospholipid molecules?
Hydrophilic regions are the phosphate heads that face outward and interact with water, while hydrophobic regions are the fatty acid tails that face inward and away from water.
What is the role of cholesterol in the cell membrane?
Cholesterol helps maintain membrane fluidity.
What is the difference between passive and active transport mechanisms?
Passive transport involves the movement of molecules without energy expenditure, such as diffusion and osmosis, while active transport involves the movement of molecules against concentration gradients, requiring energy expenditure.
What is the purpose of carbohydrates attached to proteins or lipids in the cell membrane?
Carbohydrates attached to proteins or lipids are involved in cell signaling.
What is the significance of the cell membrane's selective permeability?
The cell membrane's selective permeability allows it to regulate what substances enter and leave the cell, maintaining cellular homeostasis and proper function.
What is tissue, and how is it defined?
A group of cells having a common origin performing more or less a common or similar function.
How do cells in a tissue originate, according to Haberlandt (1914)?
Tissue formation occurs mainly in two ways: by repeated cell division and by concrescence.
What is the relationship between tissues, tissue systems, organs, and organisms?
Tissues form tissue systems, which make up organs, and several organs constitute an organism.
Why do lower plants and animals not have tissues?
They only represent a group of cells, lacking the level of organization typical of higher organisms.
What determines the functional activities of tissues?
The functional activities of tissues are not linked to or determined by their mode of origin.
How do the cells in a tissue relate to each other?
The cells of a tissue have a common origin.
Study Notes
Cell Membrane
Structure:
- Phospholipid bilayer: a double layer of lipid molecules with phosphate heads and fatty acid tails
- Hydrophilic (water-loving) heads face outward, interacting with water
- Hydrophobic (water-fearing) tails face inward, away from water
Functions:
- Regulates what enters and leaves the cell
- Maintains cell shape and provides mechanical support
- Acts as a barrier to separate the cell from its environment
- Allows for cell signaling and communication
Components:
- Phospholipids (major component)
- Proteins (embedded in the membrane, performing various functions)
- Cholesterol (helps maintain membrane fluidity)
- Carbohydrates (attached to proteins or lipids, involved in cell signaling)
Permeability:
- Selectively permeable: allows certain substances to pass through while restricting others
- Diffusion: movement of molecules from high to low concentration
- Osmosis: movement of water molecules through the membrane to balance concentration gradients
Transport mechanisms:
- Passive transport: movement of molecules without energy expenditure (e.g., diffusion, osmosis)
- Active transport: movement of molecules against concentration gradients, requiring energy expenditure (e.g., carrier proteins, pumps)
Fluidity:
- Influenced by temperature, cholesterol, and fatty acid composition
- Important for cell membrane function and flexibility
Learn about the structure and functions of cell membranes, including the phospholipid bilayer, permeability, transport mechanisms, and fluidity. Understand how the cell membrane regulates what enters and leaves the cell and maintains cell shape.
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