Year 11 Human Biology Cells Flashcards
What is the primary characteristic of the cell membrane?
semipermeable.
Which small molecules can pass through the cell membrane?
- Glucose
- Amino acids
- Carbon dioxide
- Oxygen
- Ions
What are the two ends of phospholipid molecules?
- Hydrophobic (water-hating) end
- Hydrophilic (water-loving) end
What model describes the structure of the cell membrane?
The fluid mosaic model.
Describe the fluid mosaic model.
The fluid mosaic model proposes that protein molecules are embedded in the phospholipid bilayer like a mosaic and that membranes are fluid.
What role do cholesterol molecules play in the cell membrane?
Cholesterol molecules make the membrane more stable.
What types of molecules can move through the phospholipid bilayer?
- Lipid-soluble molecules
- Small molecules like water, urea, oxygen, and carbon dioxide
What process allows water-soluble molecules to move through the cell membrane?
Water-soluble molecules move through channels in the proteins.
Define diffusion.
Diffusion is the movement of molecules from areas of high concentration to areas of low concentration.
What is an example of diffusion?
A sugar cube dissolving in a glass of water.
What is a concentration gradient?
The difference in concentration on either side of the membrane.
Is diffusion an active or passive process?
Diffusion is a passive process.
What is facilitated diffusion?
Facilitated diffusion is the diffusion of molecules through protein channels in the membrane.
What substances are commonly transported by facilitated diffusion?
- Ions
- Glucose
- Amino acids
What is osmosis?
Osmosis is the movement of water molecules across a semipermeable membrane from an area of high concentration of water molecules to an area of low concentration.
What is required for active transport?
Energy is required for active transport.
What is the purpose of active transport?
Active transport moves substances against the concentration gradient.
What is endocytosis?
Endocytosis is the process where the cell membrane surrounds a substance and forms a vesicle to transport large molecules or particles into the cell.
Is endocytosis an active or passive process?
Endocytosis is an active process.
What is exocytosis?
Exocytosis is the process of expelling substances from the cell using vesicles.
What is an example of exocytosis?
A cell producing digestive enzymes that must be secreted into the digestive tract.
What is the surface area to volume ratio?
The surface area to volume ratio is the ratio that indicates how efficiently a cell can exchange substances with its environment.
How does the surface area to volume ratio change with cell size?
The surface area to volume ratio decreases with increased size of cells.
What shape increases the surface area to volume ratio?
Shapes that are longer and flatter increase the surface area to volume ratio.
