Question 1

A spherical cell has a radius of 2 $$ \mu m . $$Calculate its surface area-to-volume ratio, and explain why this ratio is important for cellular function.

Accepted Answer

Surface area-to-volume ratio is $$\frac{3}{r}$$, so for $$r = 2\ \mu m$$, the ratio is $$1.5\ \mu m$$^{-1}$$. A higher ratio allows for more efficient exchange of materials with the environment.

Question 2

Which of the following best explains why mitochondria and chloroplasts are considered evidence for the endosymbiont theory?

Accepted Answer

They contain their own circular DNA and ribosomes similar to those of prokaryotes.

Question 3

A freshwater plant cell is placed in a hypertonic solution. What will most likely happen to the cell, and why?

Accepted Answer

Water will leave the cell, causing the plasma membrane to pull away from the cell wall (plasmolysis) due to osmosis.

Question 4

Which of the following adaptations would most likely increase the surface area-to-volume ratio in an animal, and why is this beneficial?

Accepted Answer

Development of microvilli in the intestines, which increases surface area for nutrient absorption.

Question 5

Which statement best describes the orientation of hydrophobic and hydrophilic regions in a transmembrane protein within the phospholipid bilayer?

Accepted Answer

Hydrophobic regions are embedded within the membrane's interior, while hydrophilic regions are exposed to the aqueous environments on either side.

Question 6

A patient is given an intravenous solution that is hypotonic relative to their blood plasma. What is the most likely effect on their red blood cells?

Accepted Answer

Water will enter the cells by osmosis, causing them to swell and possibly lyse.

Question 7

Which of the following best describes the role of ATP in active transport across the plasma membrane?

Accepted Answer

ATP provides energy to change the shape of transport proteins, allowing substances to move against their concentration gradients.

Question 8

Which of the following is a function of the Golgi apparatus in eukaryotic cells?

Accepted Answer

Modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles.

Question 9

A cell is observed to have a large central vacuole, chloroplasts, and a cell wall. Which type of cell is this, and what is the function of the central vacuole?

Accepted Answer

Plant cell; the central vacuole stores water, ions, and contributes to turgor pressure.

Question 10

Which of the following best explains how cholesterol affects membrane fluidity at different temperatures?

Accepted Answer

Cholesterol reduces membrane fluidity at high temperatures and prevents solidification at low temperatures.

Question 11

A cell is placed in a solution with a water potential ($$\Psi) of$$ $$-0.5$$ MPa. The cell's internal water potential is $$-0.7$$ MPa. In which direction will water move, and why?

Accepted Answer

Water will move out of the cell because water moves from higher to lower (more negative) water potential.

Question 12

Which of the following is a key difference between prokaryotic and eukaryotic cells?

Accepted Answer

Eukaryotic cells have membrane-bound organelles, while prokaryotic cells do not.

Question 13

Which of the following best describes the function of peroxisomes in eukaryotic cells?

Accepted Answer

They break down fatty acids and detoxify harmful substances using enzymes that produce hydrogen peroxide.

Question 14

Which scenario best illustrates cotransport in a biological membrane?

Accepted Answer

A proton gradient created by ATP-driven pumps is used to drive the uptake of sucrose into the cell.

Question 15

Which of the following best describes the Fluid Mosaic Model of the cell membrane?

Accepted Answer

A dynamic structure with proteins and lipids moving laterally within the bilayer.

Question 16

Which of the following is a function of the cytoskeleton in eukaryotic cells?

Accepted Answer

Providing structural support and facilitating movement of organelles within the cell.

Question 17

A white blood cell engulfs a bacterium by surrounding it with its plasma membrane, forming a vesicle. What is this process called?

Accepted Answer

Phagocytosis, a type of endocytosis.

Question 18

Which of the following best explains why unsaturated fatty acids increase membrane fluidity?

Accepted Answer

Their kinks prevent tight packing of phospholipids, allowing more movement.

Question 19

Which of the following is true about the selective permeability of biological membranes?

Accepted Answer

Small, nonpolar molecules can cross easily, while large or charged molecules require transport proteins.

Question 20

A vesicle containing neurotransmitters fuses with the plasma membrane of a neuron, releasing its contents into the synaptic cleft. What is this process called?

Accepted Answer

Exocytosis.

Unit 3 Study Guide: A Tour of the Cell & Membrane Structure and Function

Guida di studio - Domande di pratica

Study guide - Flashcard