Ch. 6, 7, 12 Quiz

Small and hydrophobic molecules pass through a cell membrane most easily because the lipid bilayer of the membrane is made up of hydrophobic tails that repel water. This allows small and hydrophobic molecules to easily dissolve in the lipid bilayer and diffuse across the membrane. Large polar molecules, ionic molecules, and large hydrophobic molecules face more difficulty passing through the membrane due to their size or charge, and may require specific transport proteins or channels. Monosaccharides like glucose are small but polar, so they may require specific transport proteins to cross the membrane.

Diffusion is a passive process that involves the movement of molecules from areas of high concentration to areas of lower concentration. This process does not require energy input and does not involve integral proteins in the cell membrane. It occurs spontaneously and is driven by the random motion of molecules.

Integral membrane proteins are usually transmembrane proteins because they are embedded within the lipid bilayer of the cell membrane. These proteins have regions that span across the entire membrane, allowing them to interact with both the intracellular and extracellular environments. Transmembrane proteins play crucial roles in various cellular processes such as cell signaling, transport of molecules across the membrane, and cell adhesion. Therefore, it is accurate to say that integral membrane proteins are usually transmembrane proteins.

Plant cells are usually in a hypotonic solution because they have a rigid cell wall that prevents them from bursting when water enters the cell. The cell wall exerts an inward pressure on the cell membrane, creating a turgid state. On the other hand, animal cells are usually in an isotonic solution, meaning the concentration of solutes inside and outside the cell is balanced. This allows for the free movement of water across the cell membrane without causing the cell to shrink or swell. Therefore, the statement that plant cells are usually in a hypotonic solution and animal cells are usually in an isotonic solution is true.

During prophase, the chromosomes condense and become visible under a microscope. This is the first phase of mitosis where the nuclear envelope starts to break down, and the spindle fibers begin to form. The condensation of chromosomes allows for easier separation and distribution of genetic material during cell division.

The major reason for size limits on certain types of cells is the need for surface area sufficient to support the cell's functions. As cells increase in size, their volume increases faster than their surface area. This can lead to a decreased surface area-to-volume ratio, making it more difficult for the cell to exchange nutrients, gases, and waste efficiently. Therefore, size limits are necessary to ensure that cells have enough surface area to adequately support their metabolic activities.

Cyclins are proteins that play a crucial role in regulating the cell cycle. They change in concentration during different stages of the cell cycle, specifically binding to and activating cyclin-dependent kinases (CDKs). This interaction triggers various cellular processes, such as DNA replication and cell division. ATPases are enzymes that hydrolyze ATP to release energy, kinetochores are protein structures that help in chromosome segregation during cell division, centrioles are involved in cell division and formation of the mitotic spindle, and proton pumps are membrane proteins that transport protons across cell membranes. None of these options accurately describe proteins involved in regulating the cell cycle and changing in concentration, making cyclins the correct answer.

Chloroplasts and mitochondria are the organelles associated with energy transformation. Chloroplasts are found in plant cells and are responsible for photosynthesis, where light energy is converted into chemical energy in the form of glucose. Mitochondria are found in both plant and animal cells and are responsible for cellular respiration, where glucose is broken down to release energy in the form of ATP. Together, chloroplasts and mitochondria play a crucial role in energy conversion and are essential for the functioning of cells.

Phagocytosis is the process by which white blood cells engulf and ingest bacteria. This process involves the formation of pseudopodia, which surround and engulf the bacteria, forming a phagosome. The phagosome then fuses with lysosomes, forming a phagolysosome, where the bacteria are broken down and destroyed. Therefore, phagocytosis is the correct answer for this question.

Non-dividing cells are in the G0 phase. In this phase, cells are not actively dividing and are considered to be in a resting state. They may temporarily exit the cell cycle or enter a quiescent state where they can remain for an extended period of time. Cells in G0 can re-enter the cell cycle and start dividing again if they receive appropriate signals or stimuli.

The formation of the cell plate across the middle of the cell is actually a characteristic of plant cells undergoing cytokinesis, not animal cells. In animal cells, cytokinesis occurs through a process called cleavage furrowing, where the cell membrane pinches inwards to divide the cell into two daughter cells. Therefore, the statement is false.

The endoplasmic reticulum is not part of a prokaryotic cell. Prokaryotic cells, such as bacteria, do not have a membrane-bound organelle like the endoplasmic reticulum. The endoplasmic reticulum is found in eukaryotic cells and plays a role in protein synthesis and lipid metabolism. In prokaryotic cells, DNA is present, along with other structures like the cell wall, ribosomes, and plasma membrane.

Each cell division doubles the number of cells. So, starting with one cell (the fertilized egg), the first division produces 2 cells, the second division produces 4 cells, the third division produces 8 cells, the fourth division produces 16 cells, and the fifth division produces 32 cells. Therefore, after five cell divisions, an early embryo would have 32 cells.

When distilled water, which is hypotonic compared to the cells, is injected into the patient's vein, it will cause the patient's blood cells to swell. This is because the concentration of solutes inside the cells is higher than that of the distilled water, causing water to move into the cells through osmosis. As a result, the cells will take in water and expand, leading to cell swelling.

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During the S phase of the cell cycle, DNA is replicated. This phase occurs after the G1 phase and before the G2 phase. In the S phase, the DNA is duplicated to ensure that each daughter cell receives a complete set of genetic information during cell division. This replication process is essential for cell growth and development.

Tay-Sachs disease is a genetic abnormality that causes the accumulation and clogging of cells with large, complex lipids. The lysosome, a membrane-bound organelle, is responsible for breaking down and recycling cellular waste, including lipids. In Tay-Sachs disease, a defect in the lysosomal enzymes leads to the buildup of lipids, causing the symptoms associated with the condition. Therefore, the lysosome must be involved in this condition.

A lack of appropriate cell death could logically result in a tumor because if cells do not undergo programmed cell death (apoptosis) when they should, they can continue to divide and accumulate, leading to the formation of a tumor. This can occur due to mutations or dysregulation in the genes and signaling pathways involved in apoptosis.

The major structural components of the cell membrane are phospholipids and proteins. Phospholipids form a lipid bilayer that makes up the basic structure of the membrane, while proteins are embedded within the lipid bilayer and perform various functions such as transport, signaling, and cell adhesion. Nucleic acids, cellulose, and cholesterol are not major structural components of the cell membrane.

The organelles that contain genetic information are ribosomes, mitochondria, chloroplasts, and nucleus. Ribosomes are responsible for protein synthesis and contain RNA molecules that carry genetic information. Mitochondria and chloroplasts have their own DNA and are involved in energy production and photosynthesis, respectively. The nucleus contains the majority of the cell's genetic material in the form of DNA, which carries instructions for cell function and development.