Transport across cell membranes Flashcards
What is the function of phospholipids
. Forms bilayer
. Selectively permeable- only allowing non-polar molecules through into cells
. Compartmentalisation- maintain different concentrations either side of the membrane
. Flexible shape
What if the function of phospholipids within cells
. Selectively permeable- only allowing non-polar molecules through into organelles
. Separates metabolic reaction and enzymes inside organelles
. Surface for reactions
What is the function of cholesterol
. Regulates fluidity
. Hydrophobic
What is the function of proteins
. Stability to membrane
. Can be extrinsic or intrinsic
. Channel proteins for polar molecules in facilitated diffusion
. Carrier proteins for active transport of polar molecules
What is the function of glycoproteins/ glycolipid
. Receptor site for hormones
. Act as recognition sites for molecules and cells
. Helps cells to attach to each other to form tissue
Define fluid ( fluid mosaic)
Molecule can move relative to one another, allowing flexibility
Define mosaic ( fluid mosaic)
Made of both phospholipids and proteins
How does steepness affect the rate of transport
The greater the difference in concentration between the two sides of the membranes the faster the rate of transport
How does surface area affect rate of transport
The greater the surface area the faster the rate of transport. This is because more molecules or ions can cross the membrane at any on time
How does the number of proteins affect the rate of transport
A larger number of channel and carrier proteins in the membrane the faster the rate of transport. This is because more molecules or ions can cross the membrane at any one time
How does temperature affect the rate of transport
Higher temperature give molecules or ions more kinetic energy so the faster the rate of transport. Molecules can move faster.
Define diffusion
Net movement of molecules or ions from a higher concentration to lower concentration. Down a concentration gradient until equilibrium. Passively
Define facilitated diffusion
Net movement of molecules or ions from higher concentration to lower concentration. Down a concentration gradient until equilibrium. Passively. Using channel and carrier proteins.
Define osmosis
The diffusion of water molecules from a higher water potential to a lower water potential. Down a water potential gradient until equilibrium. Passively across membrane or through aquaporins
Define solute
Ion/ Molecule that dissolves in a solvent
Define solvent
Substance solute dissolves in
Define incipient plasmolysis
The protoplast no longer presses on the cell wall
Define protoplasts
Consists of outer cell-surface membrane, nucleus, cytoplasm, and inner vacuole membrane
Define plamolysed
The protoplast and cell contents pull away from the cell wall
Define turgid
The protoplast is pushed against the cell wall
How does a high water potential outside a cell affect an animal cell
- Water enters by osmosis
- Cell swells and bursts
How does an equal water potential affect an animal cell
- There is no net movement of water by osmosis
- No change to cell
How does a lower water potential outside a cell affect animal cell
- Water leaves by osmosis
- Cell shrinks
How does a higher water potential outside the cell affect plant cells
- Water enters by osmosis
- Protoplast swells
- Cell becomes turgid
How does an equal water potential affect plant cells
- No net movement of water by osmosis
- No change to the protoplast
- Incipient plasmolysis
How does a lower water potential outside the cell affect plant cells
- Water leaves by osmosis
- Protoplast shrinks, the cell is plasmolysed
- Cell becomes flaccid
Define active transport
The movement of ions or molecules from a lower concentration to a higher concentration. Against a concentration gradient. Using ATP and carrier proteins
Describe the co-transport and absorption of glucose in the ileum
. Sodium ion leaves the epithelial cell into the blood
. By active transport using the Na+ / K + pump
. So sodium ions concentration inside epithelial cell is lower than lumen of ileum
. Sodium ion moves from the lumen of the ileum into the epithelial cell by facilitated diffusion down a concentration gradient
. Glucose absorbed with sodium ion against glucose concentration gradient
. Glucose moves into blood from epithelial cell by facilitated diffusion
