Understanding the Endoplasmic Reticulum and Golgi Body

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Biology › Understanding the Endoplasmic Reticulum and Golgi Body

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1

Steroids are an important component of cell membranes and gonadal hormones. What organelle is most important in the synthesis of steroids?

Smooth endoplasmic reticulum

Rough endoplasmic reticulum

Golgi apparatus

Lysosomes

Explanation

Steroids are a type of lipid that include cholesterol (needed for cell membranes) and gonadal hormones (estrogen, testosterone, and progesterone). Since they are lipids, steroids are synthesized in the smooth endoplasmic reticulum, the site of lipid synthesis.

Remember that smooth endoplasmic reticulum also plays a role in detoxification of harmful chemicals.

Rough endoplasmic reticulum is used to produce proteins that will be secreted from the cell, including most peptide hormones. The Golgi apparatus is used to modify these proteins and create vesicles for protein transport. Lysosomes contain hydrolytic enzymes that digest cellular wastes.

2

Which organelle is most important for a person who has consumed too much alcohol?

Smooth endoplasmic reticulum

Rough endoplasmic reticulum

Mitochondria

Ribosomes

Explanation

The question states that the person has consumed too much alcohol, which means that the body must detoxify the chemicals from alcohol. You are therefore looking for the organelle that participates in detoxification of chemicals. In addition to synthesizing lipids, the smooth endoplasmic reticulum plays an important role in detoxification of chemicals. This detoxification process occurs in the liver, which contains an abundance of smooth endoplasmic reticulum.

Rough endoplasmic reticulum and ribosomes are involved in protein synthesis, and mitochondria are the site of energy (ATP) production.

3

Lipid synthesis occurs in which of the following cell organelles?

Smooth endoplasmic reticulum

Lysosome

Golgi apparatus

Rough endoplasmic reticulum

Vacuole

Explanation

Smooth endoplasmic reticulum (ER) is devoted almost exclusively to the manufacture of lipids, and in some cases the metabolism of lipids and their associated products. Smooth ER synthesizes lipids, phospholipids, and steroids. It also carries out the metabolism of carbohydrates and drug detoxification. The smooth ER of the endoplasmic reticulum lacks ribosomes, hence the name smooth ER.

4

Which of the following organelles is responsible for detoxification?

Smooth endoplasmic reticulum

Rough endoplasmic reticulum

Mitochondria

Golgi apparatus

Ribosome

Explanation

Smooth endoplasmic reticulum(ER) is responsible for the detoxification of a number of organic chemicals. The smooth ER converts organic substances into water and other soluble products to allow for excretion. Large amounts of smooth ER are found in liver cells, where products of natural metabolism, drugs, and alcohol are detoxified. Fun fact: the smooth ER can double its surface area within a few days then return to its normal size once the assault has subsided.

5

The liver is plays a vital role in alcohol detoxification. Which of the following would one most likely observe when viewing a liver cell under a microscope?

Smooth endoplasmic reticulum

Rough endoplasmic reticulum

Mitochondria

Nuclei

Explanation

Cells associated with the smooth endoplasmic reticulum (ER) are responsible for cellular detoxification; therefore, one would expect to see a higher concentration of smooth ER in liver cells.

6

Which organelle is used for detoxifying drugs?

Smooth endoplasmic reticulum

Rough endoplasmic reticulum

Lysosome

Golgi apparatus

Explanation

The smooth endoplasmic reticulum has a variety of functions, one of which involves the detoxification of drugs and pollutants found in the body. Enzymes found in the smooth endoplasmic reticulum allow it to break down harmful drugs and toxins. Cells in the liver, called hepatocytes, have particularly large smooth endoplasmic reticulum regions, allowing them to be especially efficient at clearly toxins from the body.

The rough endoplasmic reticulum and Golgi apparatus are involved in protein modification, folding, and packaging. Lysosomes house enzymes that aid in breakdown of macromolecules and cellular wastes; they are specialized to remove biological waste, but are not well-suited to remove ingested toxins.

7

The main function of the nucleus is __________.

DNA and RNA synthesis

produce proteins

produce enzymes

detoxification of toxins and poisons

Explanation

The nucleus is the site of DNA replication, and transcription, which is the process by which DNA is converted to RNA. Enzymes are a class of proteins. All protein synthesis occurs in the ribosomes, some of which are on the endoplasmic reticulum (rough ER), and some are floating in the cytoplasm. Detoxification of harmful substances is carried out by the smooth endoplasmic reticulum.

8

The smooth endoplasmic reticulum's main function is __________.

synthesize lipids and detoxify harmful substances

synthesize RNA

synthesize proteins

regulate water intake

Explanation

Smooth endoplasmic reticulum (ER) synthesizes lipids and detoxifies harmful substances. RNA synthesis occurs in transcription but does not involve Smooth ER. Proteins are synthesized by Rough ER and ribosomes. Water intake is regulated by vacuoles, which are present in a few animal cell types.

9

Which of the following is not a function of the smooth endoplasmic reticulum?

Protein synthesis

Lipid synthesis

Transport of proteins

Detoxification of the cell

Transportation of cellular materials

Explanation

The smooth endoplasmic reticulum has a variety of functions. Proteins can be packaged and transported through the cell by the smooth endoplasmic reticulum, as can other cellular components and materials. The membrane around the smooth endoplasmic reticulum can be used to create intracellular vesicles. The smooth endoplasmic reticulum is also responsible for using these vesicles to interface with the plasma membrane, synthesizing phospholipids to repair and grow the membrane surface area. The smooth endoplasmic reticulum also contains enzymes responsible for degrading inorganic toxins, such as alcohol and drugs. This organelle is especially prevalent in hepatocytes (liver cells) where the blood if filtered and toxins are removed for degradation.

Protein synthesis requires the action of ribosomes, which can be found in the cytosol or embedded in the membrane of the rough endoplasmic reticulum.

10

A researcher observes two organelles under the microscope. He notices that organelle A contains more amino acids than organelle B. What might the researcher conclude about the two organelles?

Organelle A is rough endoplasmic reticulum and it contains ribosomes

Organelle A is smooth endoplasmic reticulum and it contains ribosomes

Organelle B is rough endoplasmic reticulum and it contains ribosomes

Organelle B is smooth endoplasmic reticulum and it contains ribosomes

Explanation

The question states that organelle A has more amino acids. This means that organelle A has more proteins than organelle B. Remember that rough endoplasmic reticulum (rough ER) is termed ‘rough’ because it contains ribosomes on its surface. These ribosomes give it a rough appearance under the microscope. Ribosomes are the site of protein synthesis, therefore, rough ER will contain more proteins (and amino acids).

We cannot draw any conclusions about organelle B, since most organelles contain fewer amino acids and proteins than the rough endoplasmic reticulum.

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