chapter 3 Flashcards
(55 cards)
What is the cell theory?
A cell is the structural and functional unit of life.
It states that all living organisms are composed of cells, and all cells arise from preexisting cells.
What determines the biochemical functions of cells?
The shape of the cell and specific subcellular structures.
Structure and function are complementary in cells.
How many different types of human cells are there?
Over 250 different types.
These types differ in size, shape, and subcellular components.
What are the three basic parts of human cells?
- Plasma membrane
- Cytoplasm
- Nucleus
What are extracellular materials?
Substances found outside cells.
This includes extracellular fluids, cellular secretions, and extracellular matrix.
What is the function of the plasma membrane?
Acts as an active barrier separating intracellular fluid from extracellular fluid.
It controls what enters and leaves the cell.
What model describes the structure of the plasma membrane?
Fluid mosaic model.
It illustrates the flexible lipid bilayer and the arrangement of proteins within it.
What is glycocalyx?
Sugars (carbohydrates) sticking out of the cell surface.
It functions as specific biological markers for cell-to-cell recognition.
What are the main components of the lipid bilayer?
- 75% phospholipids
- 5% glycolipids
- 20% cholesterol
What are the two types of membrane proteins?
- Integral proteins
- Peripheral proteins
What characterizes integral proteins?
Firmly inserted into the membrane and most are transmembrane proteins.
They have both hydrophobic and hydrophilic regions.
What are the functions of peripheral proteins?
- Enzymes
- Motor proteins
- Cell-to-cell connections
What are tight junctions?
Integral proteins on adjacent cells fuse to form an impermeable junction.
They prevent fluids and most molecules from moving between cells.
What are desmosomes?
Rivet-like cell junctions formed by linker proteins interlocking.
They allow ‘give’ between cells, reducing the possibility of tearing under tension.
What are gap junctions?
Transmembrane proteins form tunnels allowing small molecules to pass between cells.
They are used to spread ions and electrical signals quickly.
What are the two essential ways substances cross the plasma membrane?
- Passive transport
- Active transport
What is passive transport?
Movement of substances across the plasma membrane without energy input.
Types include simple diffusion, facilitated diffusion, and osmosis.
What factors influence the speed of diffusion?
- Concentration
- Molecular Size
- Temperature
What is simple diffusion?
Passive diffusion of lipid-soluble and nonpolar substances through the membrane.
Examples include oxygen and carbon dioxide.
What is facilitated diffusion?
Transport of certain molecules down their concentration gradient via carrier or channel proteins.
It applies to hydrophobic molecules like glucose.
What is osmosis?
Movement of solvent (e.g., water) across a selectively permeable membrane.
Water moves from areas of low solute concentration to high solute concentration.
What is tonicity?
Ability of a solution to change the shape or tone of cells by altering their internal water volume.
Solutions can be isotonic, hypertonic, or hypotonic.
What happens in a hypertonic solution?
Water flows out of the cell, resulting in cell shrinking (crenation).
This occurs because the solution has a higher osmolarity than the cell.
What happens in a hypotonic solution?
Water flows into the cell, resulting in cell swelling and potentially bursting (lysing).
This occurs because the solution has a lower osmolarity than the cell.
