Bio 10 HW 4

Which components form the structure of the plasma membrane?

A double layer of phospholipids with embedded proteins

You measure the concentration of a polar molecule inside and outside of a cell. You find that the concentration is high and gradually increasing inside the cell. You also measure the ATP concentration inside the cell and find that it is dropping. Your best hypothesis for the process that is occurring would be:

Active transport

Extremely small viruses are still too large to enter cells by passive transport. What process brings viruses into a host cell?

Endocytosis

Phagocytic white blood cells digest many of the invasive bacteria that enter the human body. How could a bacterial cell enter a white blood cell to be digested?

Endocytosis

Why are monosaccharides used by body cells?

For energy production

If a drop of purple dye is added to a water-filled vase of white flowers, how will the purple dye move through the water?

From high concentrations of purple dye to low concentrations

Which of the following is the function of cholesterol in the cell membrane?

Helping to maintain fluidity in the membrane

Which process does not involve molecules moving across cell membranes?

Hydrogenation

If the solution surrounding a cell contains more solute than the cytoplasm inside the cell, the outside solution is said to be:

Hypertonic

Facilitated diffusion is similar to simple diffusion because

In both, substances move from areas of high concentration to low concentration

What is the function of the plasma membrane in a photosynthetic eukaryotic cell

It isolates the cell's contents from the external environment

What is the function of the plasma membrane in a photosynthetic eukaryotic cell?

It isolates the cell's contents from the external environment

What is diffusion?

Molecules moving from high concentrations to low concentrations

Which statement best summarizes the differences between osmosis and diffusion?

Osmosis deals only with water

How are large substances moved during exocytosis?

Out of the cell

Hydrophobic molecules can pass freely through the plasma membrane, but ions and polar molecules are impeded by the hydrophobic core. For this reason, plasma membranes can be considered:

Partially permeable

The principle components of cell membranes are:

Phospholipids

Some antibiotics disrupt bacterial phospholipids. Which cell component would be affected by such antibiotics?

Plasma membrane

What type of molecules, embedded in phospholipid bilayers, transport hydrophilic molecules into or out of the cell?

Proteins

Imagine a balloon is made from a membrane that's permeable to water but not sugar molecules. How would the balloon be affected if it is filled with a 50% sugar solution and then placed in a beaker of water?

The balloon would get larger as it gains water.

What do you think would happen to an animal cell that was placed into a drop of 100% pure water?

The cell will swell up and eventually burst

Elodea is a freshwater aquatic plant that is often used as aquarium vegetation. How would an Elodea plant be affected by immersion in a saltwater aquarium?

The cells of the plant would shrink as water from the plant moved into the aquarium

A scientist isolates a mutant of a gated ion channel that transports ions into the cell in the presence of a particular chemical signal. She determines that the mutation causes the channel to remain open even in the absence of any chemical signal. She measures concentrations of the ion on either side of the membrane and finds that the concentration is higher inside the cell than outside at the beginning of the experiment. After an hour, she measures the concentrations again. What do you expect she will find?

The concentration of ion inside the cell is equal to the concentration outside the cell

True/false: diffusion occurs because of random molecular movement

True

Which molecule requires the most ATP to be used for moving across a plasma membrane?

an ion moving against a concentration gradient

Phospholipids assemble spontaneously into bilayers driven by the attraction of their "tail" portions to each other and of their "head" portions to each other. The tail regions are:

hydrophobic

The fatty-acid tails of a phospholipid are:

hydrophobic

You are bored at a lunch meeting and surreptitiously place a raisin in your glass of water. The raisin swells to twice its original size. Relative to the water, the raisin must have been

hypertonic

The main lipid component of plasma membranes is ____________.

phospholipids

Cells contain proteins that help transport substances from the exterior to the interior of the cell. Where are these proteins found?

plasma membrane

In general, which of the following is largely responsible for moving substances across the plasma membrane, communicating with other cells, and identifying the cell?

proteins

True/False: Recognition proteins of the plasma membrane help in the immune response

true

A phospholipid has ______ fatty acids attached to it.

two

Yeast cells take up glucose (a sugar) to use as their primary source of energy. Typically, glucose concentrations outside yeast cells are far lower than glucose concentrations inside the cells. Therefore, for yeast to take up glucose, they must:

use active transport to move glucose up (against) its concentration gradient.