Which of following is classified as a long bone?

To understand this question, we need to understand passive immunity and how it differs from active immunity.

1. What Is Passive Immunity?

Passive immunity occurs when a person receives antibodies from another source instead of producing them themselves.

In passive immunity:

• The body does not create its own antibodies
• Antibodies are transferred from another individual
• Protection occurs immediately
• The immunity is temporary because the body does not form memory cells

2. Example of Passive Immunity

One of the most common natural examples of passive immunity occurs between a mother and her baby.

Antibodies are transferred in two main ways:

During pregnancy

Maternal antibodies (IgG) cross the placenta to protect the fetus.

After birth

Antibodies (IgA) are transferred through breast milk.

These antibodies help protect the baby from infections while the baby's immune system is still developing.

3. Why the Correct Answer Is Passive Immunity

The option:

“A mother passes antibodies to her child through breast milk.”

is passive immunity because:

• The baby receives antibodies directly
• The baby did not produce the antibodies itself
• The protection is temporary

Why the Other Options Are Incorrect

Immunization leads to the activation of B-cell proliferation.

This describes active immunity, where the body produces its own antibodies after vaccination.

After primary exposure to an antigen, memory T cells remain to respond to a secondary exposure.

This describes immune memory, which is part of active immunity, not passive immunity.

Exposure to a virus leads to the production of antibodies that can bind to the virus.

This also describes active immunity, because the body is producing its own antibodies.

Key Takeaway Points

Passive immunity = receiving antibodies

Antibodies come from another person or source.

Passive immunity provides immediate protection

Protection begins right away because antibodies are already present.

Passive immunity is temporary

Because the body does not create memory cells, the protection does not last long.

Common examples of passive immunity

TEAS Exam Memory Trick

Think of this phrase:

Passive = Passing antibodies

If antibodies are given to you, it is passive immunity.

If your body makes the antibodies, it is active immunity.

This question tests your understanding of gene expression and protein synthesis inside the cell.

The key statement in the question is:

“The cell is able to make copies of its genetic information but is unable to produce encoded proteins.”

This tells us that:

• DNA replication is working
• But protein synthesis is not occurring

The cellular structure responsible for protein synthesis is the ribosome.

1. How Genetic Information Becomes Protein

Cells use a process called gene expression to convert genetic information into proteins.

This occurs in two major steps:

Step 1: Transcription

DNA → mRNA

• Occurs in the nucleus
• The DNA code is copied into messenger RNA (mRNA)

The question states the cell can make copies of its genetic information, meaning this step is working.

Step 2: Translation

mRNA → Protein

• Occurs at the ribosome
• Ribosomes read the mRNA instructions and build proteins from amino acids

If the cell cannot produce proteins, the issue is likely with the ribosomes, where translation occurs.

2. What Ribosomes Do

Ribosomes are the cellular structures responsible for protein synthesis.

Their function is to:

• Read mRNA instructions
• Assemble amino acids
• Build polypeptide chains (proteins)

Ribosomes can be found:

• Floating freely in the cytoplasm
• Attached to the rough endoplasmic reticulum (RER)

Without ribosomes, the cell cannot produce proteins, even if DNA and mRNA are present.

Why the Other Options Are Incorrect

Acrosome

The acrosome is a structure found in sperm cells that contains enzymes used to penetrate the egg during fertilization.

It has nothing to do with protein production in general cells.

Centrosome

The centrosome organizes microtubules and helps form the mitotic spindle during cell division.

It is involved in cell division, not protein synthesis.

Golgi Apparatus

The Golgi apparatus modifies, sorts, and packages proteins after they are made.

It does not produce proteins.

If ribosomes fail, proteins never reach the Golgi.

Key Takeaway Points

Ribosomes make proteins

Protein synthesis occurs during translation at ribosomes.

DNA → RNA → Protein

This process is called the central dogma of molecular biology.

If proteins cannot be produced, suspect ribosomes

Even if DNA replication and transcription work normally, protein synthesis cannot occur without ribosomes.

Ribosomes are found in two locations

• Free ribosomes → make proteins used inside the cell
• Rough ER ribosomes → make proteins for export or membranes

TEAS Exam Memory Trick

Think of ribosomes as protein factories.

If a question mentions:

• Protein production
• Translation
• mRNA being converted to protein

➡ The answer is usually ribosomes.

This question involves phase changes and gas pressure.

The key concept here is sublimation, which is when a substance changes directly from a solid to a gas without passing through the liquid phase.

Dry ice is the solid form of carbon dioxide (CO₂). When dry ice sublimates, it turns directly into CO₂ gas.

1. What Happens When Dry Ice Sublimates?

When dry ice changes from solid CO₂ to gaseous CO₂:

• Solid CO₂ molecules become free-moving gas molecules
• The gas molecules spread out and occupy more space
• The number of gas particles in the container increases

Because the container is sealed, the gas cannot escape.

2. Why Pressure Increases

Pressure in a gas occurs when gas molecules collide with the walls of a container.

As dry ice sublimates:

1. More CO₂ gas molecules are produced.
2. These gas molecules move freely throughout the container.
3. They collide with the container walls more frequently.

More collisions with the container walls result in greater pressure.

So the best explanation is that gas CO₂ particles occupy more space, leading to increased pressure.

3. Gas Behavior vs Solid Behavior

When CO₂ changes from solid → gas, the particles become much farther apart and mobile, which increases pressure inside a sealed container.

Why the Other Options Are Incorrect

Gas CO₂ molecules move faster when CO₂ is a solid.

Molecules in a solid move much less than gas molecules. Gas molecules move faster because they have greater freedom of movement.

CO₂ molecules combine to form larger molecules in the gas phase.

CO₂ molecules do not combine during sublimation. They remain individual CO₂ molecules.

CO₂ particles exert less force on the container walls as a gas.

Gas particles actually exert more force because they collide with the container walls frequently.

Key Takeaway Points

Sublimation

Sublimation is the change of state from:

Solid → Gas

Example: Dry ice (solid CO₂) → CO₂ gas

Gas pressure

Gas pressure is caused by collisions of gas particles with container walls.

More particles = more collisions = higher pressure

Gas particles spread out

Gas molecules move freely and occupy more space than solid particles.

Sealed containers trap gases

If gas forms inside a sealed container, the pressure will increase because the gas cannot escape.

TEAS Exam Memory Trick

Remember:

More gas particles → More collisions → Higher pressure

This question focuses on the pancreas and blood glucose regulation, specifically the endocrine portion of the pancreas called the islets of Langerhans.

These islets contain several types of hormone-producing cells that regulate blood sugar.

1. The Islets of Langerhans in the Pancreas

The pancreas contains clusters of endocrine cells called the islets of Langerhans. Each cell type secretes a different hormone that helps regulate blood glucose.

2. Role of Beta Cells

Beta cells are responsible for producing insulin, the hormone that lowers blood glucose levels.

Insulin works by:

• Allowing glucose to enter body cells
• Promoting glucose storage in the liver as glycogen
• Lowering the amount of glucose circulating in the bloodstream

Without insulin, glucose cannot enter most cells effectively.

3. What Happens in Type 1 Diabetes

Type 1 diabetes mellitus is an autoimmune disease in which the body's immune system attacks and destroys beta cells in the pancreas.

Because beta cells are destroyed:

• The pancreas cannot produce insulin
• Blood glucose levels rise dramatically
• Cells cannot use glucose properly for energy

As a result, individuals with type 1 diabetes must receive insulin injections to regulate their blood sugar.

This is why type 1 diabetes is also called insulin-dependent diabetes mellitus.

Why the Other Options Are Incorrect

F cells

F cells produce pancreatic polypeptide, which regulates pancreatic secretions and digestion but does not control blood glucose directly.

Alpha cells

Alpha cells produce glucagon, which raises blood glucose levels by stimulating the liver to release stored glucose.

Destruction of alpha cells would reduce glucagon but would not cause insulin deficiency.

Delta cells

Delta cells produce somatostatin, which inhibits the release of both insulin and glucagon. They regulate hormone balance but are not responsible for insulin production.

Key Takeaway Points

Beta cells produce insulin

Insulin is the hormone responsible for lowering blood glucose levels.

Type 1 diabetes is an autoimmune disease

The immune system destroys beta cells, preventing insulin production.

Without insulin, glucose cannot enter cells efficiently

This causes high blood sugar (hyperglycemia).

People with type 1 diabetes require insulin therapy

Because their pancreas cannot produce insulin, they must take external insulin to survive.

TEAS Exam Memory Trick

Remember:

B = Beta = Blood sugar lowering

Beta cells → Insulin → lowers blood glucose

If beta cells are destroyed → Type 1 diabetes.

This question is asking which cell structure is a system of interconnected tubes and is involved in protein production. The correct answer is the rough endoplasmic reticulum (rough ER).

1. What is the Rough Endoplasmic Reticulum?

The rough endoplasmic reticulum is a network of membranous sacs and interconnected tubes found inside eukaryotic cells. It is called “rough” because ribosomes are attached to its outer surface, giving it a bumpy appearance under a microscope.

Those ribosomes are the key reason the rough ER is involved in protein production.

2. How the Rough ER Helps Make Proteins

Protein production happens in stages:

Step 1: DNA instructions are transcribed into mRNA

This occurs in the nucleus.

Step 2: Ribosomes read the mRNA

Ribosomes attached to the rough ER translate the mRNA code into a chain of amino acids.

Step 3: The rough ER begins processing the protein

Once the protein is made, the rough ER helps:

• fold the protein correctly
• modify it
• transport it to other parts of the cell, often to the Golgi apparatus

So while ribosomes directly assemble proteins, the rough ER is the interconnected tube system associated with making and processing proteins.

3. Why “interconnected tubes” matters

The wording of the question points strongly to the endoplasmic reticulum, because the ER is literally a membrane network spread throughout the cytoplasm.

There are two types of ER:

• Rough ER → has ribosomes, involved in protein synthesis
• Smooth ER → no ribosomes, involved in lipid synthesis and detoxification

Since the question specifies protein production, it must be the rough endoplasmic reticulum.

Why the Other Options Are Incorrect

the cytoskeleton

The cytoskeleton is a framework of protein fibers that helps the cell maintain its shape, move, and transport materials internally.

It is not the organelle primarily responsible for protein production.

the lysosome

A lysosome contains digestive enzymes that break down waste materials, damaged organelles, and foreign substances.

Its role is digestion and recycling, not protein production.

basal bodies

Basal bodies help organize microtubules and are involved in forming cilia and flagella.

They are not involved in protein synthesis.

Key Takeaway Points

1️⃣ Rough ER is the protein-processing membrane network

If a question asks about:

• interconnected tubes
• ribosomes attached
• protein production

the answer is usually rough endoplasmic reticulum.

2️⃣ Ribosomes make proteins, but rough ER supports and processes them

Ribosomes do the direct assembly of amino acids, while the rough ER helps with:

• protein folding
• modification
• transport

3️⃣ Smooth ER and rough ER have different jobs

• Rough ER → proteins
• Smooth ER → lipids, detoxification, calcium storage

4️⃣ Golgi comes after rough ER

Proteins made on the rough ER are usually sent to the Golgi apparatus for further modification and packaging.

TEAS Exam Memory Trick

Think:

Rough ER = Ribosomes = Proteins

The word rough helps you remember that it has ribosomes attached.

The original hypothesis says that parasitic worm infestation is damaging to the host. Then the new finding adds an important detail: worm infestation can relieve the effects of certain autoimmune disorders.

That means the hypothesis should not be thrown out completely, but it should be revised to include this newly discovered benefit in some situations.

Choice B is best because it directly matches the new evidence:

• the worms can relieve effects
• relieving effects means they can reduce severity
• this applies to certain autoimmune disorders, not all disorders

Why the other choices are not correct:

A. Lack of worm infestations is the cause of some autoimmune disorders.
This goes too far. The question only says worm infestation can relieve the effects of some autoimmune disorders. It does not say that not having worms causes those disorders.

C. Worm infestations exacerbate the body's immune reactions.
“Exacerbate” means make worse. But the new finding says worm infestation can relieve effects, so this is the opposite of what the evidence supports.

D. Worm infestation prevents the body from immune malfunction.
This is too absolute. The question says worm infestation can relieve the effects of certain autoimmune disorders. It does not say worm infestation completely prevents immune malfunction.

Key Reasoning

When a hypothesis is modified based on new findings, the best answer usually:

• keeps as much of the original idea as possible
• adds only what the new evidence supports
• avoids extreme words like cause, prevents, or always, unless the evidence clearly proves them

Here, the evidence supports a limited revision:
worm infestation may be harmful in general, but it may also reduce the severity of some autoimmune conditions.

Takeaway Points

• A hypothesis should be revised, not automatically discarded, when new evidence appears.
• The best revision is the one that matches the evidence exactly.
• Be careful with extreme answer choices that go beyond the information given.
• In science questions, wording matters:
  • relieve effects = reduce severity
  • not necessarily cause, prevent, or cure

This question tests your knowledge of the types of body membranes and their functions.

The cutaneous membrane is the membrane that forms the skin, which is the largest organ of the human body.

The cutaneous membrane covers the external surface of the body and protects internal tissues from environmental damage, pathogens, dehydration, and physical injury.

Unlike other membranes, the cutaneous membrane is dry, meaning it is not kept moist by secretions.

The skin consists of two main layers:

1. Epidermis

The outer layer of the skin.

Key characteristics:

• Made of keratinized stratified squamous epithelium
• Provides protection
• Contains melanin-producing cells (melanocytes)

2. Dermis

The deeper connective tissue layer.

Contains:

• Blood vessels
• Nerves
• Hair follicles
• Sweat glands
• Sebaceous glands

Together, these layers form the cutaneous membrane, which acts as the body's protective barrier.

Types of Body Membranes

The human body has four major membrane types:

The cutaneous membrane is unique because it is the only dry membrane in the body.

Why the Other Options Are Incorrect

Serous

Serous membranes line internal body cavities and cover organs.

Examples include:

• Pleura (lungs)
• Pericardium (heart)
• Peritoneum (abdominal organs)

They secrete serous fluid, which reduces friction between organs.

Synovial

Synovial membranes line joint cavities.

They produce synovial fluid, which lubricates joints and allows smooth movement.

Example: knee joint, elbow joint.

Peritoneum

The peritoneum is actually a specific type of serous membrane that lines the abdominal cavity and covers abdominal organs.

It is not associated with the skin.

Key Takeaway Points

The cutaneous membrane is the skin

It covers the entire external surface of the body.

Skin has two main layers

• Epidermis
• Dermis

The skin is the body's largest organ

It protects against:

• pathogens
• dehydration
• temperature changes
• UV radiation

Cutaneous membrane is the only dry membrane

Other membranes (serous, mucous, synovial) produce fluids.

TEAS Exam Memory Trick

Think:

C → Cutaneous → Covering

The cutaneous membrane covers the body.

This question tests knowledge of the female urinary system and the functions of its structures.

The urethra is the tube that carries urine from the urinary bladder to the outside of the body.

After urine is produced by the kidneys and stored in the bladder, it must exit the body through a passageway. This passageway is the urethra.

Urinary pathway in the body

The flow of urine follows this sequence:

1. Kidneys – filter blood and produce urine
2. Ureters – transport urine from the kidneys to the bladder
3. Bladder – stores urine temporarily
4. Urethra – carries urine from the bladder to the outside of the body

Therefore, the structure that connects the bladder to the outside is the urethra.

Female Urethra

In females, the urethra is:

• about 3–4 cm long
• shorter than the male urethra
• located anterior to the vagina

Because it is shorter, bacteria can reach the bladder more easily, which is why urinary tract infections (UTIs) are more common in females.

Why the Other Options Are Incorrect

Vagina

The vagina is part of the female reproductive system, not the urinary system.

Functions:

• receives sperm during sexual intercourse
• acts as the birth canal
• allows menstrual flow to leave the body

It does not carry urine from the bladder.

Fallopian tubes

Fallopian tubes are part of the female reproductive system.

Their function is to:

• transport eggs from the ovaries to the uterus
• provide the site where fertilization typically occurs

They have no role in urine transport.

Ureter

The ureters transport urine from the kidneys to the bladder.

They do not connect the bladder to the outside of the body.

Key Takeaway Points

Urine leaves the body through the urethra

The urethra connects the bladder to the outside.

Urinary system pathway

The flow of urine is:

Kidneys → Ureters → Bladder → Urethra

Ureters vs Urethra

Students often confuse these.

Female urethra is shorter

This increases the risk of urinary tract infections (UTIs).

TEAS Exam Memory Trick

Remember:

Ureter → Up to bladder
Urethra → Out of body

Skeletal muscle contraction occurs when a motor neuron communicates with a muscle fiber at a specialized junction called the neuromuscular junction (NMJ). The neurotransmitter responsible for transmitting the signal from the motor neuron to the muscle cell is acetylcholine (ACh).

Step-by-Step Process of Skeletal Muscle Contraction

1. Nerve impulse travels down a motor neuron
   • A signal from the brain or spinal cord travels along the motor neuron toward the muscle.
2. Arrival at the neuromuscular junction
   • The nerve impulse reaches the axon terminal of the motor neuron.
3. Release of acetylcholine
   • Vesicles in the neuron release acetylcholine into the synaptic cleft (the small gap between neuron and muscle).
4. Binding to receptors
   • Acetylcholine binds to receptors on the muscle fiber membrane (sarcolemma).
5. Generation of a muscle action potential
   • This causes sodium channels to open, leading to depolarization of the muscle cell membrane.
6. Calcium release
   • The signal spreads through the muscle fiber and triggers the sarcoplasmic reticulum to release calcium ions.
7. Muscle contraction
   • Calcium allows actin and myosin filaments to interact, producing muscle contraction.
8. Termination of signal
   • The enzyme acetylcholinesterase breaks down acetylcholine, stopping the signal and allowing the muscle to relax.

Why the Other Options Are Incorrect

Dopamine

Dopamine is a neurotransmitter primarily involved in:

• movement regulation in the brain
• reward and motivation pathways
• coordination of voluntary movement

It does not directly cause skeletal muscle contraction at the neuromuscular junction.

Epinephrine

Epinephrine (adrenaline) is a hormone and neurotransmitter involved in the fight-or-flight response.

It affects:

• heart rate
• blood pressure
• metabolism

However, it does not directly trigger skeletal muscle contraction.

Serotonin

Serotonin mainly regulates:

• mood
• sleep
• appetite
• emotional processing

It functions primarily in the central nervous system and digestive system, not in skeletal muscle contraction.

Key Takeaway Points

Acetylcholine controls skeletal muscle contraction

At the neuromuscular junction, acetylcholine is the neurotransmitter that activates muscle fibers.

Neuromuscular junction = communication site

The neuromuscular junction is where:

• a motor neuron
• communicates with a skeletal muscle cell

Calcium enables contraction

Acetylcholine triggers calcium release, which allows:

actin + myosin → muscle contraction

Acetylcholinesterase stops contraction

The enzyme acetylcholinesterase breaks down acetylcholine, allowing muscles to relax.

TEAS Exam Memory Trick

Remember:

ACh = Activate Contraction of skeletal muscle

Acetylcholine is the only neurotransmitter used at the neuromuscular junction.

This question involves Mendelian genetics, specifically dominant and recessive alleles.

The problem describes two separate traits:

1️⃣ Ear type
2️⃣ Hair length

We must determine the genotype that produces attached ears and short hair.

Step 1: Ear Type Genetics

The question states:

• F = Free ears (dominant)
• f = Attached ears (recessive)

Because attached ears are recessive, the dog must inherit two recessive alleles to show this trait.

Therefore the genotype must be:

ff

If even one F allele were present (Ff), the dog would have free ears.

Step 2: Hair Length Genetics

The question also states:

• S = Short hair (dominant)
• s = Long hair (recessive)

Since short hair is dominant, the dog only needs at least one S allele to show short hair.

Possible genotypes for short hair are:

• SS
• Ss

Among the answer choices, the genotype that includes short hair is Ss.

Step 3: Combine Both Traits

We combine the two genotypes:

Final genotype:

ffSs

Why the Other Options Are Incorrect

FfSs

This would produce free ears, because F is dominant.

ffss

This would produce attached ears AND long hair, because ss causes long hair.

Ffss

This would produce free ears and long hair, which does not match the question.

Key Takeaway Points

1️⃣ Dominant vs Recessive Traits

2️⃣ Recessive traits require two recessive alleles

For the dog to have attached ears, the genotype must be:

ff

3️⃣ Dominant traits only require one dominant allele

For short hair, either genotype works:

• SS
• Ss

4️⃣ Multiple traits are solved separately

When solving genetics problems:

1. Identify genotype for each trait separately
2. Combine the results

TEAS Exam Memory Trick

Remember:

Recessive trait = double letters

Examples: