What did I learn? Score Your Quiz (Module 6)

In this module you learned about several types of steroid hormones that are made in the body. Which of the following steroid hormones is important in increasing muscle size?
1. Cortisol
  Not correct. Cortisol is one of the glucocorticoids that is synthesized in the adrenal gland. It actually causes muscle breakdown. The synthetic version, cortisone, is used as a powerful anti-inflammatory agent.
2. Estrogen
  No, estrogen is a female sex steroid synthesized in the ovaries to help in the process of ovulation. It also helps maintain the mineral density in bones.
3. Testosterone
  You are right. Testosterone is a male sex steroid synthesized in the testes to produce male sexual characteristics (androgen). It also can increase muscle size in exercising males and females (anabolic).
4. Progesterone
  Sorry, this isn’t right. Progesterone is a female sex steroid synthesized in the ovaries to help prepare the uterus for pregnancy (promotes endometrial cell differentiation).
Steroids are lipophilic molecules that must cross the cell membrane in order to bind to its receptor inside the cell. What form of membrane transport is used?
1. Active transport
  Sorry, this isn’t right. Active transport is a process that requires energy to move a substance against the concentration gradient. It involves the help of a protein carrier, or transporter.
2. Passive diffusion
  Very good! The non-polar nature of steroids allow them to move easily with their concentration gradient into the cell. Their non-polar nature attracts them to the hydrophobic core of the membrane lipid bilayer and this helps the steroid to move in the direction of the cytoplasm. No energy is required.
3. Facilitated diffusion
  Not correct. Facilitated diffusion also occurs with concentration gradient, but it requires a protein carrier to help. No energy is required, but the carriers can become saturated, limiting the transport. A good is example is the movement of the testosterone-anadrogen receptor into the nucleus, across the nuclear membrane.
4. Filtration
  No, sorry. Filtration is a process of solute moving through a pore in the membrane, with the concentration gradient. It is often aided by pressure. It is limited by the size of the compound and it does not require any energy.
Anabolic steroids increase the ability of DNA to make more muscle proteins. The protein synthesis is directed by 2 major processes. Which of the following describes the steps to protein synthesis?
1. translation, followed by transcription
  Sorry, you’ve got it backwards. Translation occurs second. It is the process of assembling a sequence of amino acids to form a protein using instructions brought by the mRNA to the ribosome. It takes place in the cytosol. Transcription occurs first. It is the process of generating a specific mRNA from the DNA template, with the help of several enzymes. It takes place in the nucleus.
2. translation, followed by transportation
  Not correct. Translation occurs second. It is the process of assembling a sequence of amino acids to form a protein using instructions brought by the mRNA to the ribosome. It takes place in the cytosol. Transportation is the movement of a molecule from one site to another, or your ride from school back to your house.
3. transcription, followed by conscription
  You’re half right. Transcription is the process of generating a specific mRNA from the DNA template, with the help of several enzymes. It takes place in the nucleus. Conscription is the process of recruitment or enlistment to be in the armed forces or maybe in the school play.
4. transcription, followed by translation
  Yea, you got it right! Transcription is the process of generating a specific mRNA from the DNA template, with the help of several enzymes. It takes place in the nucleus. Translation is the process of assembling a sequence of amino acids to form a protein using instructions brought by the mRNA to the ribosome. It takes place in the cytosol.
There are several steps involved in muscle contraction. Which of the following sequences is correct?
1. Acetylcholine binds to a receptor on the muscle cell, activating DNA. DNA causes calcium to be released from the sarcoplasmic reticulum, causing the tendons to shorten.
  Try again. DNA does not play a role in muscle contraction and tendons lengthen when a muscle contracts.
2. Acetylcholine binds to a receptor on the muscle cell, calcium is released from the sarcoplasmic reticulum, sarcomeres shorten due to the thin actin filaments sliding over the thick myosin filaments.
  Great! Muscle contraction is initiated when acetylcholine binds to its receptor, triggering release of calcium from inside the muscle cell into the sarcoplasm. This causes the sliding of actin and myosin filaments to shorten the sarcomeres, contracting the muscle.
3. Acetylcholine binds to a receptor on the muscle cell, calcium is released from the sarcoplasmic reticulum, sarcomeres shorten causing the thin actin filaments to twist around the thick myosin filaments.
  Not quite. Shortening of the sarcomeres results from the sliding of actin filaments over the myosin filaments.
4. Acetylcholine binds to a receptor on the tendons, calcium is released from the sarcoplasmic reticulum, the tendons pull on the sarcomeres causing them to lengthen.
  Well, you’re only right for the receptor. Actually, some nucleic acids in DNA can serve as a receptor for certain drugs.
The production of hormones in our bodies is under the control of positive and negative feedback. This keeps levels of hormones in the normal range. However, hormone production changes when we take drugs that bind to the hormone receptors. What will happen to the athlete who takes anabolic steroids over a long period of time?
1. His testes will stop making testosterone
  You are right. The high amount of anabolic steroid in the blood signals the hypothalamus (i.e., binds to androgen receptors there) in the brain to stop producing gonadotropin releasing hormone. This stops the pituitary gland from making LH and FSH. These hormones signal the testes to make testosterone – without them, no testosterone is synthesized.
2. His testes will increase the production of testosterone
  No, the opposite happens. The high amount of anabolic steroid in the blood signals the hypothalamus in the brain to stop producing gonadotropin releasing hormone. This stops the pituitary gland from making LH and FSH. These hormones signal the testes to make testosterone – without them, no testosterone is synthesized.
3. His hypothalamus will increase production of gonadotropin releasing hormone
  No, the opposite happens. The high amount of anabolic steroid in the blood signals the hypothalamus in the brain to stop producing gonadotropin releasing hormone.
4. His pituitary will increase production of LH and FSH
  No, the opposite happens. The high amount of anabolic steroid in the blood signals the hypothalamus in the brain to stop producing gonadotropin releasing hormone. This stops the pituitary gland from making LH and FSH.