A cell is unable to synthesize lipids. Which of its cell organelles might be defective?
- A.Smooth endoplasmic reticulum
- B.Golgi bodies
- C.Lysosomes
- D.Mitochondria
Correct answer
Explanation
The correct answer is A, Smooth endoplasmic reticulum. Lipids, including steroids and the phospholipids of membranes, are made by the smooth endoplasmic reticulum, so a defect there would stop lipid synthesis.
The endoplasmic reticulum is a network of membrane tubes in the cytoplasm. Rough ER carries ribosomes on its surface and makes proteins. Smooth ER has no ribosomes; it makes lipids and steroid hormones, and in liver cells it also helps remove poisons and drugs from the body. The lipids and proteins made by the ER are used to build new cell membranes, a process called membrane biogenesis. Cells that make steroid hormones, such as those of the adrenal cortex and gonads, are rich in smooth ER.
B is wrong because Golgi bodies modify, package and send out materials made by the ER; they do not make lipids.
C is wrong because lysosomes contain digestive enzymes that break down worn-out parts and germs.
D is wrong because mitochondria carry out cellular respiration and make ATP, the cell's energy currency.
Exam tip: rough ER → proteins; smooth ER → lipids and steroids, detoxification; Golgi → packaging; lysosome → suicide bag; mitochondria → powerhouse.
Practice Questions
View allWhich one of the following is not true for anodizing process?
- A.It makes aluminium corrosion resistant.
- B.Metals like aluminium, titanium and magnesium can be anodized.
- C.Clean aluminium article is the anode and oxygen gas is evolved at the cathode.
- D.It is used in aircraft industry.
Show answer
In anodizing the clean aluminium article is indeed the anode, but oxygen is released at the anode, not at the cathode; hydrogen is released at the cathode.
Read the full explanation →Which one of the following statements is not correct?
- A.The response of the ear to sound of increasing intensity is approximately logarithmic.
- B.The sensitivity of the human ear does not vary with the frequency of the sound.
- C.When two or more waves traverse the same medium, the displacement of any element of the medium is the algebraic sum of the displacements due to each wave.
- D.Longitudinal waves can travel in all media—solids, liquids and gases.
Show answer
The statement that the sensitivity of the human ear does not vary with frequency is false, because the ear is far more sensitive to some frequencies than to others.
Read the full explanation →Kwashiorkor disease in children is caused by
- A.sufficient carbohydrates but less fats in diet
- B.sufficient carbohydrates and fats but deficient proteins in diet
- C.sufficient vitamins but deficient fats in diet
- D.sufficient fats but deficient vitamins in diet
Show answer
Kwashiorkor is a disease of protein deficiency in a child who still gets enough calories. It usually appears when a child is weaned from breast milk onto a starchy diet with little protein.
Read the full explanation →Which one of the following is the correct order of pH for the given substances?
- A.Coffee < Lemon juice < Milk of magnesia < Blood
- B.Milk of magnesia < Blood < Coffee < Lemon juice
- C.Lemon juice < Blood < Coffee < Milk of magnesia
- D.Lemon juice < Coffee < Blood < Milk of magnesia
Show answer
Arranged from most acidic to most basic, the four substances fall in exactly this order. Lemon juice, rich in citric acid, has a pH of about 2 to 2.5.
Read the full explanation →Which one of the following diseases may be caused by the deficiency of vitamin C?
- A.Rickets
- B.Rabies
- C.Hepatitis
- D.Scurvy
Show answer
Scurvy is caused by a lack of vitamin C, or ascorbic acid, which the body needs to make collagen, the protein that holds skin, gums and blood vessels together.
Read the full explanation →