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Chapter 32: Problem 16

Some unicellular organisms, such as the amoeba, ingest food by endocytosis. The food vesicle fuses with a lysosome, which digests the food. Waste is excreted by which process? a. exocytosis b. filtration c. osmoregulation d. dilatation

Short Answer

Expert verified
a. exocytosis

Step by step solution

01

Understand Endocytosis and Lysosome Function

Endocytosis is the process by which a cell engulfs a particle or molecule to form a vesicle. The vesicle is then brought into the cell, where it can fuse with a lysosome. Lysosomes contain enzymes that digest the ingested material.
02

Identify How Cells Excrete Waste

Cells must expel the waste products generated by digestion. The process by which these waste products are expelled from the cell is critical to understanding the options.
03

Evaluate the Options

a. Exocytosis is the process where vesicles inside the cell fuse with the cell membrane, releasing their contents outside the cell. b. Filtration involves the movement of water and solutes across a membrane due to hydrostatic pressure and is not related to vesicle release. c. Osmoregulation refers to the control of water and electrolyte balance within a cell or organism. d. Dilatation means dilation or expansion and does not relate to waste excretion.
04

Determine the Correct Answer

The process by which waste is excreted from the cell is exocytosis, where vesicles containing waste material fuse with the cell membrane to expel waste products.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

endocytosis
Endocytosis is an essential process for cells, especially in unicellular organisms like amoebas, to obtain nutrients. This process begins when the cell engulfs a particle or molecule from its external environment, forming a vesicle around it.

There are different types of endocytosis:
  • Phagocytosis: Often referred to as 'cell eating,' this involves engulfing large particles like food or bacteria.
  • Pinocytosis: Known as 'cell drinking,' this involves engulfing fluids and dissolved solutes.
  • Receptor-mediated endocytosis: This is a more selective method where specific molecules bind to receptor proteins on the cell surface before being engulfed.
Once the vesicle containing the ingested material is inside the cell, it typically fuses with a lysosome to break down the substances.
lysosome function
Lysosomes play a crucial role in the cell's digestive process. These are small organelles filled with enzymes that break down various types of biomolecules.

When a vesicle formed by endocytosis fuses with a lysosome, the enzymes inside the lysosome go to work:
  • Breaking down complex molecules into simpler ones.
  • Degrading damaged cellular components for recycling.
  • Destroying pathogens that may have been engulfed during phagocytosis.
Lysosomes ensure that cells can reuse the fundamental building blocks of the ingested material and maintain cellular health.
waste excretion in cells
Once the lysosome has digested the material within the vesicle, waste products are generated. Cells need to expel these waste products to maintain homeostasis and proper function. This is where exocytosis comes into play.

Exocytosis is the process where vesicles, which contain cellular waste, fuse with the plasma membrane of the cell. Here is how it works:
  • The vesicle moves to the cell membrane.
  • The membrane of the vesicle fuses with the cell's outer membrane.
  • The waste material is expelled outside the cell.
This process ensures that cells can efficiently remove waste, relying on exocytosis to ensure a clean and balanced internal environment.

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Most popular questions from this chapter

Which toxic substance is formed by nitrogenous waste? a. chlorine b. potassium c. ammonia d. sodium

Explain two different excretory systems other than the kidneys. a. (1) An excretory mechanism occurs in annelids through the Malpighian tubules. Metabolic wastes like uric acid freely diffuse into the tubules. Uric acid is excreted as a thick paste or powder. (2) An excretory mechanism occurs in the flatworm, which contains two tubules with cells called flame cells. They have cilia that propel waste matter down the tubules and out of the body. b. (1) An excretory mechanism occurs in arthropods through a pore called the nephridiopore. These organisms have a system for tubular reabsorption. (2) An excretory mechanism occurs in annelids through the Malpighian tubules. Metabolic wastes like uric acid freely diffuse into the tubules. Uric acid is excreted as a thick paste or powder. c. (1) An excretory mechanism is endocytosis, which occurs when vacuoles merge with the cell membrane and excrete cellular wastes in the environment. (2) An excretory mechanism occurs in annelids through a pore called the nephridiopore. These organisms have a system for tubular reabsorption. d. (1) An excretory mechanism is exocytosis, which occurs when vacuoles merge with the cell membrane and excrete cellular wastes in the environment. (2) An excretory mechanism occurs in flatworms which consists of two tubules containing cells called flame cells. They have a cluster of cilia that propel waste matter down the tubules and out of the body.

How does the loop of Henle act as a countercurrent multiplier? a. The descending limb of the loop of Henle is water permeable, so the water flows from the filtrate to the interstitial fluid. Osmolality in the limb decreases, and it is lower inside the loop than in the interstitial fluid. As the filtrate enters the ascending limb, Na+ and Clions exit through ion channels present in the cell membrane. Further up, only sodium is passively transported out of the filtrate. b. The descending limb of the loop of Henle is water impermeable, so the water flows from the filtrate to the interstitial fluid. Osmolality in the limb increases, and it is higher inside the loop than in the interstitial fluid. As the filtrate enters the ascending limb, Na+ and Clions exit through ion channels present in the cell membrane. Further up, only sodium is passively transported out of the filtrate. c. The descending limb of the loop of Henle is water impermeable, so the water flows from the filtrate to the interstitial fluid. Osmolality in the limb increases, and it is higher inside the loop than in the interstitial fluid. As the filtrate enters the ascending limb, Na+ and Clions exit through ion channels present in the cell membrane. Further up, sodium is actively transported out of the filtrate, and chlorine ions follow. d. The descending limb of the loop of Henle is water permeable, so the water flows from the filtrate to the interstitial fluid. Osmolality in the limb increases, and it is higher inside the loop than in the interstitial fluid. As the filtrate enters the ascending limb, Na+ and Clions exit through ion channels present in the cell membrane. Further up, sodium is actively transported out of the filtrate, and chlorine ions follows.

What is the difference between an osmoregulator and an osmoconformer? a. Osmoregulators can change the osmotic pressure of their body fluids, while osmoconformers cannot. b. Osmoconformers can change the osmotic pressure of their body fluids, while osmoregulators cannot. c. Osmoregulators match the osmotic pressure of their cells with that of the environment, while osmoconformers do not. d. Osmoconformers match the osmotic pressure of their cells with that of the environment, while osmoregulators do not.

What is the 鈥渇ight or flight鈥� response, and what is its effect on the excretory system? a. Aldosterone is the 鈥渇ight or flight鈥� that is released by the adrenal medulla under extreme stress. This hormone constricts the smooth muscles of the blood vessels. It constricts the afferent arterioles, causing the flow of blood into the nephrons to stop. b. Epinephrine and norepinephrine are the 鈥渇ight or flight鈥� hormones that are released by the adrenal medulla and the nervous system, respectively, under extreme stress. These hormones constrict the smooth muscles of the blood vessels. They constrict the afferent arterioles, causing the flow of blood into the nephrons to stop. c. ADH is the 鈥渇ight or flight鈥� hormone that is released by the adrenal medulla under extreme stress. This hormone constricts the smooth muscles of the blood vessels. It constricts the efferent arterioles, causing the flow of blood into the nephrons to stop. d. Epinephrine and norepinephrine are the 鈥渇ight or flight鈥� hormones that are released by the adrenal medulla and the nervous system, respectively, under extreme stress. These hormones constrict the smooth muscles of the blood vessels. They constrict the efferent arterioles, causing the flow of blood into the nephrons to stop.
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