Unit 2 Test Review

Question 1

What are ribosomes composed of, and what is their main function?

Answer 1

Ribosomes are composed of ribosomal RNA (rRNA) and proteins. Their main function is to synthesize proteins according to the mRNA sequence.

Question 2

Why are ribosomes found in all forms of life?

Answer 2

They represent the common ancestry of all known life.

Question 3

What are the two forms of the endoplasmic reticulum, and what are their respective functions?

Answer 3

The two forms are smooth and rough ER. Rough ER is associated with membrane-bound ribosomes and compartmentalizes the cell, while smooth ER functions in detoxification and lipid synthesis.

Question 4

What is the Golgi Apparatus, and what are its main functions?

Answer 4

The Golgi Apparatus is a membrane-bound structure consisting of flattened membrane sacs. It is responsible for the correct folding and chemical modification of newly synthesized proteins and their packaging for trafficking.

Question 5

What structural feature differentiates mitochondria from other organelles, and what is its significance?

Answer 5

Mitochondria have a double membrane, with the inner membrane forming convoluted folds, which increases the surface area for metabolic reactions.

Question 6

What is the function of lysosomes, and what do they contain?

Answer 6

Lysosomes are membrane-enclosed sacs containing hydrolytic enzymes used for intracellular digestion.

Question 7

What is the role of vacuoles, particularly in plant cells?

Answer 7

Vacuoles are membrane-bound sacs that play roles in storage and maintaining turgor pressure in plant cells. The large central vacuole in plants stores water and inorganic ions.

Question 8

Where are chloroplasts found, and what is their primary function?

Answer 8

Chloroplasts are found in photosynthetic algae and plants. They are responsible for photosynthesis and contain a double outer membrane.

Question 9

How does the endoplasmic reticulum (ER) contribute to cellular function?

Answer 9

The ER provides mechanical support, conducts protein synthesis on membrane-bound ribosomes, and plays a role in intracellular transport.

Question 10

What is the significance of the double membrane of mitochondria?

Answer 10

The double membrane of mitochondria allows compartmentalization for different metabolic reactions, aiding in efficient energy production.

Question 11

What is the role of lysosomes in cellular processes?

Answer 11

Lysosomes are crucial for intracellular digestion, recycling organic materials, and programmed cell death (apoptosis).

Question 12

What are the roles of vacuoles in plant cells?

Answer 12

Vacuoles help store and release macromolecules and waste products, as well as retain water to maintain turgor pressure.

Question 13

Why does the folding of the inner membrane of mitochondria increase ATP production?

Answer 13

The folding increases surface area, allowing more sites for ATP synthesis during cellular respiration.

Question 14

Where do the light-dependent reactions of photosynthesis occur, and what structures are involved?

Answer 14

The light-dependent reactions occur in the grana of the chloroplasts, which are stacks of thylakoids containing chlorophyll pigments and electron transport proteins.

Question 15

Where do the carbon fixation reactions of photosynthesis occur?

Answer 15

Carbon fixation reactions (Calvin cycle) occur in the stroma, the fluid inside the chloroplast.

Question 16

What is the Krebs cycle, and where does it occur?

Answer 16

The Krebs cycle, or citric acid cycle, is part of cellular respiration and occurs in the mitochondrial matrix.

Question 17

How does the surface area-to-volume ratio affect the exchange of materials in cells?

Answer 17

A higher surface area-to-volume ratio allows more efficient exchange of materials, while a lower ratio makes the process less efficient.

Question 18

Why do cells remain small in size?

Answer 18

Cells remain small to maintain a high surface area-to-volume ratio, ensuring efficient transport of materials in and out of the cell.

Question 19

How do complex cellular structures, such as membrane folds, enhance material exchange?

Answer 19

Membrane folds increase the surface area, allowing more space for molecules to be exchanged efficiently with the environment.

Question 20

What strategies have organisms evolved to exchange materials efficiently with the environment?

Answer 20

Specialized structures like vacuoles, cilia, and stomata have evolved to assist in efficient exchange of molecules with the environment.

Question 21

What is the Fluid Mosaic Model of the plasma membrane?

Answer 21

The Fluid Mosaic Model describes the cell membrane as a flexible layer made of phospholipids, with proteins, cholesterol, glycoproteins, and glycolipids embedded within it.

Question 22

How do phospholipids contribute to the structure of the cell membrane?

Answer 22

Phospholipids have hydrophilic heads facing the aqueous environments and hydrophobic tails facing each other, forming a bilayer that acts as a selective barrier.

Question 23

What roles do embedded proteins play in the plasma membrane?

Answer 23

Embedded proteins can be hydrophilic or hydrophobic, playing roles in transport, signal reception, and maintaining the internal environment of the cell.

Question 24

What is passive transport, and why is it important for cells?

Answer 24

Passive transport is the net movement of molecules from an area of high concentration to an area of low concentration without the use of metabolic energy. It is crucial for importing materials like nutrients and exporting waste products in cells.

Question 25

How does active transport differ from passive transport?

Answer 25

Active transport requires the input of energy (usually in the form of ATP) to move molecules from areas of low concentration to areas of high concentration, against their concentration gradient, while passive transport does not require energy.

Question 26

What is the role of the sodium-potassium pump in active transport?

Answer 26

The sodium-potassium pump moves 3 Na+ ions out of the cell and 2 K+ ions into the cell using energy from ATP. This process maintains the cell’s membrane potential and concentration gradients of sodium and potassium.

Question 27

What are electrogenic pumps, and why are they important for cells?

Answer 27

Electrogenic pumps are transport proteins that generate voltage across a membrane by moving charged particles. For example, the sodium-potassium pump in animal cells and the proton pump in plants, fungi, and bacteria are electrogenic pumps that help maintain the cell’s electrochemical gradient.

Question 28

Explain cotransport and give an example of how it works in the body.

Answer 28

Cotransport occurs when the movement of one substance across its concentration gradient facilitates the movement of another substance.

Question 29

What are endocytosis and exocytosis?

Answer 29

Endocytosis is the process by which cells take in large molecules or particles by engulfing them in vesicles formed from the plasma membrane. Exocytosis is the reverse process, where vesicles inside the cell fuse with the plasma membrane to release their contents outside.

Question 30

Describe the different types of endocytosis.

Answer 30

Phagocytosis: “Cell eating,” where the cell engulfs large particles, like bacteria.

Pinocytosis: “Cell drinking,” where the cell takes in fluid and dissolved solutes.

Receptor-mediated endocytosis: A specific form of pinocytosis where the cell uses receptors to capture specific molecules before taking them in.

Question 31

What is facilitated diffusion, and how is it different from simple diffusion?

Answer 31

Facilitated diffusion is a type of passive transport where molecules move down their concentration gradient with the help of transport proteins. Unlike simple diffusion, it is used for larger or charged molecules that cannot freely pass through the lipid bilayer.

Question 32

What role do aquaporins play in facilitated diffusion?

Answer 32

Aquaporins are channel proteins that facilitate the rapid movement of water molecules across cell membranes.

Question 33

How do ion channels contribute to facilitated diffusion?

Answer 33

Ion channels are proteins that create hydrophilic pathways through the membrane for ions like Na+ and K+. Some are gated and open or close in response to stimuli such as a change in charge or the binding of a molecule.

Question 34

How does osmosis differ from diffusion?

Answer 34

Osmosis is a specific type of diffusion where water molecules move across a semipermeable membrane from an area of higher water potential (lower solute concentration) to an area of lower water potential (higher solute concentration).

Question 35

Define the terms isotonic, hypertonic, and hypotonic.

Answer 35

Isotonic: Equal solute concentration on both sides of the membrane, resulting in no net movement of water.

Hypertonic: Higher solute concentration outside the cell, causing the cell to lose water and shrivel.

Hypotonic: Lower solute concentration outside the cell, causing the cell to gain water and potentially burst.

Question 36

How do cells with cell walls (like plants) handle changes in tonicity differently from animal cells?

Answer 36

Plant cells can become firm in a hypotonic environment, as the cell wall prevents them from bursting. In an isotonic environment, they become limp. In a hypertonic environment, plant cells undergo plasmolysis, where the membrane pulls away from the cell wall, causing wilting.

Question 37

How do internal membranes contribute to the compartmentalization of eukaryotic cells?

Answer 37

Internal membranes divide eukaryotic cells into different compartments, each specialized for specific functions. This organization helps prevent interference between metabolic processes and increases efficiency by creating distinct environments for enzymatic reactions.

Question 38

Why is compartmentalization important for cellular processes?

Answer 38

Compartmentalization allows cells to carry out different metabolic processes simultaneously without interference, increases surface area for reactions, and helps regulate the internal environment.

Question 39

How did membrane-bound organelles evolve in eukaryotic cells?

Answer 39

Membrane-bound organelles, like mitochondria and chloroplasts, evolved from free-living prokaryotic cells through endosymbiosis. These organelles share similarities with their prokaryotic ancestors, such as their own DNA and double membranes.

Question 40

How do prokaryotic cells differ from eukaryotic cells in terms of compartmentalization?

Answer 40

Prokaryotic cells lack membrane-bound organelles but have specialized regions within the cell that perform specific functions. Eukaryotic cells, on the other hand, have complex compartmentalization with distinct organelles enclosed by membranes.