Chapter 5 Part 1 Flashcards
From the perspective of the cell membrane, how does winter wheat survive the colder months?
Genes that increase the proportion of unsaturated fatty acids are activated.
Why do saturated fatty acids decrease the fluidity of cell membranes?
They can pack together more tightly
What does amphipathic mean?
The molecule has both a hydrophillic section and a hydrophobic section.
How does cholesterol decrease membrane fluidity while also helping to prevent low temperature solidification?
Cholesterol reduces membrane fluidity at moderate temps by restricting the flow of lipids. At low temps it hinders packing of the lipids.
What is an electrochemical gradient?
A gradient composed of an electrical gradient and a concentration gradient.
Why does K+ enter a cell
There are K+ leak channels in the cell membrane. K+ enters the cell because, in part, there is a preponderance of negatively charged amino acids at physiologic pH.
Why doesn’t potassium (K+) continue to move into the cell until all negative charges inside the cell have been satisfied?
As K moves into a cell, it creates a concentration gradient, this opposes its continued movement.
Sodium (Na+) doesn’t move into a resting cell, whereas K+ does. How is this possible?
There are no Na leak channels in the cell membrane.
What opens the Na+ gate in cells in neurons?
A stimulus such as touch, pain, light, and temperature.
Why is a membrane considered selectively permeable?
Only certain molecules are able to cross the cell membrane.
Is saltwater hypotonic or hypertonic to a red-blood cell?
Saltwater has more dissolved particles, therefore it is hypertonic to the cell.
The concentration of dissolved particles defines tonicity. What defines the movement of water?
Water moves down its concentration gradient.
What does water follows salt mean?
Water flows down its concentration gradient. For example, If there is more salt outside a cell, water will flow towards the salt (and, this is down water’s concentration gradient).
What does osmosis mean?
The diffusion (movement) of water.
