Cell Membranes Review

how does glucose diffuse through the membrane? Which diffuse through the phospholipid bilayer? Which use facilitated diffusion?

A glucose molecule is too large to pass through a cell membrane via simple diffusion. Instead, cells assist glucose diffusion through facilitated diffusion and two types of active transport.

Describe what happens to plant and animal cells in hypertonic, isotonic, and hypotonic environments.

Animal cells burst and expand in hypotonic solutions, because water is flowing into the cells, too much pressure. Normal at isotonic because flow is equal. Shriveled at hypertonic because not enough water is going in. Plant cells are wilted and droopy in hypertonic solutions because they aren't getting water. In a hypotonic solution they are healthy because of the cell wall, instead of bursting the water pushes up against the wall leaving the plants firm. In isotonic environment, the plant cell shrivels away from the cell wall , called plasmolysis.

Explain the importance of surface area and volume relationships to explaining Why cells, in general, are rather small. The adaptations/modifications that eukaryotic cells have that enable them to be much larger than prokaryotic cells.

Cells need to be small so that they have enough surface for molecules to be able to diffuse in and out. Reducing the surface area to volume ratio can also be an adaptive strategy.

simple diffusion

Diffusion that doesn't involve a direct input of energy or assistance by carrier proteins. Goes right through

What is endosymbiosis? Explain which parts of the cell arose through endosymbiosis, and list the evidence for this theory.

Endosymbiosis is a biological relationship in which one species lives inside another. About two billion years ago, an archaea cell took up a bacterial cell. All the eukaryotes resulted from this acquisition, and the bacterial cell that was taken up evolved, over time, into the mitochondria that are found in all eukaryotic cells. Later, a eukaryotic cell took up a cyanobacterium. Evidence: Both mitochondria and chloroplasts have a double membrane. mitochondria and chloroplasts have their own DNA, and this DNA has the same form as the DNA that's found in bacteria. Both mitochondria and chloroplasts have their own ribosomes, and produce some of their own proteins. Both mitochondria and chloroplasts replicate themselves independently of the host cell's cell cycle.

how do hydrophilic substances diffuse through the membrane?

In facilitated transport, hydrophilic molecules bind to a "carrier" protein; this is a form of passive transport.

receptor-mediated endocytosis

In receptor mediated endocytosis, a piece of the membrane pinches in response to some molecule that binds with a receptor embedded in the membrane.

facilitated diffusion

Movement of specific molecules across cell membranes through protein channels

Explain the functions of phospholipids

The lipid bilayer acts as a barrier to the passage of molecules and ions into and out of the cell. However, an important function of the cell membrane is to allow selective passage of certain substances into and out of cells

how do ions diffuse through the membrane?

The plasma membrane is selectively permeable; hydrophobic molecules and small polar molecules can diffuse through the lipid layer, but ions and large polar molecules cannot.

how do large molecules diffuse through the membrane?

The plasma membrane is selectively permeable; hydrophobic molecules and small polar molecules can diffuse through the lipid layer, but ions and large polar molecules cannot.

how does carbon dioxide, oxygen, diffuse through the membrane?

The structure of the lipid bilayer allows small, uncharged substances such as oxygen and carbon dioxide, and hydrophobic molecules such as lipids, to pass through the cell membrane, down their concentration gradient, by simple diffusion.

Explain the functions of all of the the structures/molecules that make up proteins. Integral, transmembrane and peripheral

They act as channels or ports, allowing the cell to take in and let out molecules that can't diffuse through the phospholipid bilayer portion of the membrane. They act as carriers, allowing the cell to perform active transport, moving molecules from low concentration to high concentration. They act as attachment points for the fibers of the cytoskeleton, allowing the cell to change its shape and move They act as membrane-embedded enzymes. They act as receptors, receiving chemical messages and relaying these messages into the cytoplasm. Any protein embedded in the phospholipid bilayer is called an integral protein. If the protein passes all the way through the membrane, it's a transmembrane protein. If the protein hangs on to the membrane, attached to the phospholipid heads, then it's a peripheral protein.

how do triglycerides diffuse through the membrane?

They are bigger molecules they can't pass through

how does water diffuse through the membrane?

Water can diffuse through the lipid bilayer even though it's polar because it's a very small molecule.

Exocytosis

a process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.

how do amino acids diffuse through the membrane?

diffuses freely

Osmosis

diffusion of water

how do steroid hormones diffuse through the membrane?

free steroid hormones enter target cells primarily by passive diffusion through the cell membrane.

Explain the functions of all of the the structures/molecules that make up membrane carbohydrates

key role in allowing the immune system to recognize a cell as belonging to the multicellular organism that it's a part of.

Explain the functions of cholesterol

lipid that plays a key role in maintaining membrane integrity and fluidity. When cell membranes become too warm, cholesterol keeps the phospholipid bilayer intact. When cell membranes become too cold, cholesterol acts like an anti-freeze, keeping the membrane fluid.

Explain how plant, animal and bacterial cells are similar and different. Which parts/organelles do they have in common? Which parts are only in animal cells? Plant cells?

plant and and animal cells are both Eukaryotic They both contain membrane-bound organelles such as the nucleus, mitochondria, endoplasmic reticulum, golgi apparatus, lysosomes. A plant cell contains a large, singular vacuole that is used for storage and maintaining the shape of the cell. animal cells have smaller vacuoles. Plant cells have a cell wall, as well as a cell membrane animal cells only have membrane. Plant and Bacteria have cell walls. Bacterial cells don't have a nucleus, mitochondria or chloroplasts like animal and plant cells.

Endocytosis

process by which a cell takes material into the cell by infolding of the cell membrane

Phagocytosis

process in which extensions of cytoplasm surround and engulf large particles and take them into the cell

Explain the structure of the phospholipid bilayer. How is it organized, and why.

the heads are facing out toward the water molecules because they are hydrophilic while the tails are facing each other in the inside and creating hydrophobic pockets. They can be in a sheet or circle shape.

pinocytosis

the membrane pinches in. The pinching in continues until a vesicle forms surrounding some of the extracellular fluid and whatever was inside it.Think of pinocytosis as the cell taking a small "sip" of the material outside the membrane.

active transport

the movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy.

passive transport

the movement of substances across a cell membrane without the use of energy by the cell

how does urea diffuse through the membrane?

urea, enter and leave cells by passive diffusion across the plasma membrane.