Section 5 reading guide Flashcards
What are the major functions of the plasma membrane?
Defines the cell, outlines its borders, determines the nature of its interaction with its environment
How does the fluid mosaic model apply to plasma membranes? What types of biomolecules are in the plasma membrane?
The fluid mosaic model applies to plasma membranes because it best describes the structure and function of the plasma membrane. The biomolecules in the plasma membrane are carbohydrates, proteins, cholesterol, and phospholipids.
What does it mean that phospholipids are amphipathic? Which part of phospholipids are hydrophobic? Hydrophilic?
Phospholipids are hydrophobic and hydrophilic. They have hydrophilic heads that interact with water, and hydrophobic tails that interact with other hydrophobic tails.
How do phospholipids arrange themselves in solution?
Phospholipids arrange themselves so the hydrophobic tails are facing each other and the hydrophilic heads are facing outwards, making contact with the water.
How does temperature affect membrane fluidity?
increased temperature leads to increased membrane fluidity, and decreased temperature leads to decreased fluidity
How does saturation level of fatty acids affect membrane fluidity?
a higher degree of saturation (more saturated fatty acids) leads to a less fluid membrane, while a higher degree of unsaturation (more unsaturated fatty acids) results in a more fluid membrane
How does cholesterol affect membrane fluidity?
Cholesterol acts as a “buffer” to regulate membrane fluidity, preventing excessive fluidity at high temperatures and preventing excessive rigidity at low temperatures by inserting itself between phospholipids and preventing them from packing too tightly together
What do we mean when we say the plasma membrane is selectively permeable?
The membrane allows certain substances to pass through the membrane and disallows the entrance of other substances.
What types of molecules can cross the lipid bilayer without extra help? Why can they do this?
small, nonpolar molecules like oxygen, carbon dioxide, and nitrogen gas. These molecules can pass through because they are hydrophobic like the tails of phospholipids.
What types of molecules cannot cross the lipid bilayer on their own? Why can’t they?
Large, charged, and polar molecules are not able to pass through the lipid bilayer because they have an opposite polarity than the hydrophobic tails, so they cannot interact with each other.
1) What is diffusion?
2) How is this an example of passive transport?
3) How does a solute’s concentration gradient affect the direction that a solute diffuses?
1)the movement of molecules from an area of high concentration of the molecules to an area with a lower concentration
2) does not require any additional energy from the cell
3) Higher the concentration gradient, the faster the rate of diffusion
How is facilitated diffusion different from passive transport?
facilitated diffusion utilizes transport proteins (like channels or carriers) embedded in the membrane to help specific molecules move down their concentration gradient
Explain the roles of channel proteins in facilitated transport
hydrophilic domains inside of the protein, hydrophobic domains outside of the protein, allows polar compounds to pass through without interacting with the nonpolar side, open all the time
Explain the roles of carrier proteins in facilitated transport
binds to a substance and changes shape to move the molecule from the cells outside to its interior, for a specific single substance
How does osmosis work? How is it similar yet different from diffusion?
Osmosis moves free water molecules through a semipermeable membrane. It is similar yet different from diffusion because they both transport material across the membrane, but osmosis transports only water.
Describe an animal cell in a hypotonic solution
A red blood cell will have a lower concentration of water outside, so water will go into the cell and cause it to swell/burst
Describe an animal cell in isotonic solution
A red blood cell will have an equal amount of water outside of the cell and inside of it. There will be no net loss/gain of water in the cell.
Describe an animal cell in hypertonic solution
A red blood cell will have a higher concentration of water inside of the cell, so it will leave the cell and cause it to shrivel/shrink.
Describe a plant cell in hypotonic solution
When there is a higher concentration of water outside of the plant cell, the cell wall prevents the plasma membrane from expanding too much, so the cell does not burst/swell.
Describe a plant cell in isotonic solution
The plant cell well not lose water or gain water.
Describe a plant cell in hypertonic solution
The cytoplasm in plants always causes the cell to be slightly hypertonic, so water always enters the cell when it is available. This strengthens the cell wall by producing turgor pressure. The cell wall is not flexible, so even if water tries to leave, it can’t.
1)What is active transport? 2)How is it similar yet different to passive transport and facilitated transport?
3)What is required for active transport to work?
1) the process of moving molecules across a cellular membrane through the use of cellular energy
2)all three methods move molecules across a cell membrane, but the key difference is that active transport requires energy to move molecules against their concentration gradient, while passive transport and facilitated transport do not
3)energy in the form of ATP
How can active transport move molecules against their concentration gradients?
The cell has to use energy to move substances against their concentration gradient. ATP is generated through the cell’s metabolism, and pumps help work against gradients.
What is the difference between primary active transport and secondary active transport?
primary active transport directly uses energy from ATP to move molecules against their concentration gradient, while secondary active transport uses the energy stored in an existing electrochemical gradient, typically created by primary active transport, to move molecules against their gradient
