AP Biology : Types of Cells and Tissues

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #481 : Cellular Biology

Which of the following occurs in a sarcomere during muscle contraction?

Possible Answers:

The A band shortens

The thick filaments move closer to one another

All of these occur during muscle contraction

The Z lines get closer to each other

The I band retains its length

Correct answer:

The Z lines get closer to each other

Explanation:

During muscle contraction thick filaments (myosin) remain stationary, while thin filaments (actin) move towards one another. In the process, the H zone and I band shorten, as the Z lines get closer together. The A band, however, never changes in length.

Example Question #482 : Cellular Biology

You observe a muscle cell that is not multinucleated. What type of muscle cell can it be?

Possible Answers:

Cardiac muscle

Skeletal muscle or cardiac muscle

Smooth muscle or skeletal muscle

Cardiac muscle or smooth muscle

Skeletal muscle

Correct answer:

Cardiac muscle or smooth muscle

Explanation:

There are three primary types of muscle: skeletal, smooth, and cardiac.

Skeletal muscle is multinucleated and striated. Smooth muscle is mononucleated and not striated. Cardiac muscle is mononucleated and striated. If we know that the muscle type is not multinucleated, then it must be mononucleated and could be either smooth muscle or cardiac muscle.

Example Question #544 : Ap Biology

Which of the following events will occur first during the initiation of a muscle contraction?

Possible Answers:

Calcium is released from the sarcoplasmic reticulum

T-tubules close, resulting in activation of the Ca2+ ATPase pump

Calcium ions bind to troponin

Motor neurons release acetylcholine

Correct answer:

Motor neurons release acetylcholine

Explanation:

There are seven steps involved in the signaling cascade from the initiation of contraction to the subsquent relaxation of muscle fibers.

  1. Motor neurons release acetylcholine (ACh), which binds to receptors on the muscle fiber's cell membrane.
  2. ACh receptor binding and activation creates an action potential that propagates along the muscle fiber membrane and down T tubules.
  3. The action potential triggers the release of Ca2+ ions from the sarcoplasmic reticulum.
  4. The released Ca2+ ions bind to troponin, which causes the displacement of tropomyosin, revealing the myosin-binding sites on the actin filament.
  5. Myosin cross-bridges attach to actin at exposed binding sites and enter a cycle of shifts to crawl along the actin fiber. This causes the sarcomere to shorten. ATP is required for this reaction.
  6. Cytosolic Ca2+ ions are removed and brought back into the sarcoplasmic reticulum by active transport (by a Ca2+ ATPase pump).
  7. Tropomyosin blockage of myosin-binding sites is restored by Ca2+ ion removal). Contraction ends and the muscle fiber relaxes.  

Example Question #545 : Ap Biology

Which two major proteins are involved in the contraction of skeletal muscle?

Possible Answers:

Actin and myosin

Myosin and ATP

Actin and ATP

Titin and actin

Correct answer:

Actin and myosin

Explanation:

The contraction of muscle cells results from the controlled interaction between actin and myosin proteins.  

Actin forms a thin filament coil structure comprised to two strands of actin and some additional regulatory proteins (troponin and tropomyosin). The actin coils are arranged above and below myosin bundles, which are also called thick filaments. One end of myosin forms a globular head shape that, in a relaxed state, is not able to bind to a site on actin. When the muscle is stimulated by a motor neuron, a signal cascade results in a conformational change that allows the myosin head to bind to actin and shift positions, allowing the muscle to shorten and contract.

While ATP is an essential component in the biochemistry of muscle contraction, it is not actually a protein. ATP is, instead, considered an amino acid derivative. Titin is the elastic protein that connects the ends of a sarcomere and allows the muscle to recoil when over-stretched.

Example Question #11 : Understanding Muscle Cells

Ca2+ ions play a key role in muscle contraction and relaxation. What would happen if the calcium ions were removed from a muscle cell?

Possible Answers:

Tropomyosin would straighten and loosen the actin coils

A Ca2+ ATPase pump would activate and actively transport Ca2+ back into the cytosol

Myosin-binding sites on actin would become exposed

Myosin-binding sites on actin would become blocked

Correct answer:

Myosin-binding sites on actin would become blocked

Explanation:

Ca2+ plays a critical role in the regulation of muscle cell contraction and relaxation. Motor neuron stimulation and subsequent the action potential signals the release of Ca2+ from the sarcoplasmic reticulum. The ions bind to troponin—a protein found in a complex with tropomyosin and bound to actin filaments—and exposes the myosin-binding sites on the actin filament by shifting the troponin-tropomyosin complex. With the myosin-binding sites revealed, the myocyte will be able to contract.

In the absence of calcium in the cell, the binding sites on the actin filament cannot be made available and myosin will not bind. No contraction will occur.

Example Question #11 : Understanding Muscle Cells

What muscle type is responsible for digestive peristalsis?

Possible Answers:

Smooth muscle and skeletal muscle

Voluntary muscle only

All muscle types may undergo peristalsis 

Skeletal muscle only

Smooth muscle only

Correct answer:

Smooth muscle only

Explanation:

There are three types of muscle tissue: skeletal muscle, smooth muscle, and cardiac muscle. Skeletal muscle is under voluntary control and is mainly responsible for locomotion and skeletal movement. Smooth muscle is involuntary and surrounds the viscera to aid in vascular constriction and organ movement. Cardiac muscle is found only in the heart and is responsible for pumping the blood.

The smooth muscle of the digestive tract is responsible for the wavelike movement of peristalsis. In humans, peristalsis is primarily responsible for helping move food down the digestive tract. It is important to understand that peristalisis is an involuntary movement.

Example Question #11 : Understanding Muscle Cells

The muscle cells that line the walls of arteries are an example of __________.

Possible Answers:

cardiac muscle

skeletal muscle

smooth muscle

artery walls are not lined with muscle cells

striated muscle

Correct answer:

smooth muscle

Explanation:

The three types of muscle in the body are smooth, skeletal, and cardiac muscle. The type of muscle lining artery walls is smooth muscle, which is also present in many organs such as the intestines and the urinary bladder. Unlike skeletal muscle, smooth muscle control is involuntary and, unlike both skeletal and cardiac muscle, it is non-striated. Smooth muscle around the arteries and arterioles is important for regulating blood pressure and directing blood flow in the body.

Example Question #11 : Understanding Muscle Cells

Which of the following are categorizations of muscle tissue?

Possible Answers:

All of these

Smooth

Muscle

Skeletal

Correct answer:

All of these

Explanation:

Muscle is a major type of tissue in the human body. They contract and enable movement. The three major types of muscle tissues include skeletal, cardiac, and smooth tissues.

Example Question #12 : Understanding Muscle Cells

Which of the following is not true regarding the structure of skeletal muscle tissue?

Possible Answers:

Skeletal muscle tissue can be "red" or "white" 

It is striated

It is made up of myocytes

It is not striated

Correct answer:

It is not striated

Explanation:

Skeletal muscle tissue is a categorization of muscle tissue that controls skeletal movement and posture. Skeletal muscle tissue is striated and made up of myocytes, which are organized into myofibrils. Skeletal muscle tissue can be categorized further into type I, type IIa, type IIx, and type IIb. These types include red—oxygenated—and white—deoxygenated—tissues.

Example Question #41 : Types Of Cells And Tissues

Skeletal muscle tissue cannot perform which of the following types of muscle contractions?

Possible Answers:

Slow contraction

Fast contraction

Voluntary

Involuntary

Correct answer:

Involuntary

Explanation:

Skeletal muscle tissue is involved in voluntary skeletal movement. Skeletal muscle can be divided into type I, type IIa, type IIx, and type IIb categories. Type I tissues exhibit slow contractions and type II are involved in fast contractions.

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