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Quizzes > Science > Biology

Test Your Hair and Scalp Properties Knowledge!

Think you know why vellus hair almost never has a medulla or which statement best describes hair porosity? Take the quiz now!

Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration of hair strands and quiz symbols for hair protein porosity and trichoptilosis on sky blue background.

This quiz helps you review why hair is approximately 90% protein and make sense of terms like porosity, trichoptilosis, and the medulla. Take a few minutes, see where you're solid or need a brush-up, then use the hair and scalp chapter for quick study and the porosity quiz to practice more.

What percentage of human hair is made up of protein?
95%
80%
90%
85%
Hair is composed of about 90% protein, mainly keratin, which provides strength and structure. The remaining 10% consists of water, lipids, pigments, and minerals. Protein's predominant role explains hair's resilience and tensile strength.
Which primary protein is found in hair structure?
Elastin
Keratin
Actin
Collagen
Keratin is the main structural protein in hair, forming long chains that give hair its strength and flexibility. Collagen and elastin are connective tissue proteins found in skin and other tissues. Actin is a muscle protein.
Which layer of the hair shaft contains the pigment that gives hair its color?
Follicle
Medulla
Cortex
Cuticle
The cortex lies beneath the cuticle and houses melanin granules responsible for hair color. The cuticle is the protective outer layer, and the medulla is a central core that may be absent in finer hair. The follicle is the skin structure that produces hair.
Disulfide bonds in hair form between which amino acid residues?
Methionine
Glycine
Alanine
Cysteine
Disulfide bonds form between sulfur atoms of two cysteine amino acids, creating cystine links that stabilize keratin's three-dimensional structure. Methionine contains sulfur but does not form disulfide bridges. Alanine and glycine are non-sulfur amino acids.
What does hair porosity measure?
Ability to absorb moisture
Protein composition
Elasticity level
Color retention
Hair porosity refers to how well hair can absorb and retain moisture. High porosity hair absorbs water quickly but can lose it just as fast, while low porosity hair resists moisture uptake. Protein composition and color retention are separate properties.
What is the term for split ends in hair?
Monilethrix
Alopecia
Trichotillomania
Trichoptilosis
Trichoptilosis is the medical term for split ends, where the hair fiber splits longitudinally. Alopecia refers to hair loss, trichotillomania to hair-pulling disorder, and monilethrix to beaded hair.
Which type of bond is the weakest in hair structure?
Peptide bond
Disulfide bond
Salt bond
Hydrogen bond
Hydrogen bonds are weak, non-covalent interactions that are easily broken by water or heat, giving hair temporary shape changes. Disulfide bonds are much stronger covalent links. Salt and peptide bonds are intermediate in strength.
What is the typical pH range of healthy hair?
8.5 to 9.5
3.0 to 4.0
7.0 to 8.0
4.5 to 5.5
Healthy hair and scalp have an acidic pH of about 4.5 to 5.5, which helps keep the cuticle closed and prevents bacteria. Alkaline products above 7 can lift the cuticle and cause damage.
Which mineral is crucial for keratin production in hair?
Potassium
Sulfur
Iron
Calcium
Sulfur is a key component of the amino acid cysteine, which forms disulfide bonds in keratin to strengthen hair. Iron and calcium have other roles in the body, and potassium regulates fluid balance.
Which of the following is not a phase of the hair growth cycle?
Catagen
Anagen
Apoptosis
Telogen
Hair growth phases include anagen (growth), catagen (regression), and telogen (rest). Apoptosis is programmed cell death and not a named hair cycle phase.
What term refers to hair loss?
Hirsutism
Alopecia
Trichorrhexis
Trichomegaly
Alopecia is the medical term for hair loss. Hirsutism refers to excessive hair growth, trichomegaly to abnormally long eyelashes, and trichorrhexis to hair shaft fractures.
Which pigment is predominant in darker hair tones?
Pheomelanin
Hemoglobin
Carotene
Eumelanin
Eumelanin is responsible for black and brown hair tones. Pheomelanin gives red and yellow hues, while carotene and hemoglobin have minimal impact on hair color.
Which layer is the outermost part of the hair shaft?
Cortex
Cuticle
Medulla
Papilla
The cuticle is the hair's outermost protective layer made of overlapping scales. The cortex lies beneath and the medulla is the central core. The papilla is part of the follicle.
Which common hair treatment uses hydrolyzed keratin?
Protein treatment
Actin peptide mask
Collagen injection
Elastin cream
Protein treatments often use hydrolyzed keratin to repair and strengthen hair by replenishing lost protein. Collagen and elastin are not typical in hair repair products. Actin peptides are not used in hair care.
What instrument is commonly used to measure hair strand diameter?
Calorimeter
Spectrophotometer
Refractometer
Micrometer
A micrometer is a precision instrument that directly measures small distances, like hair diameter. Spectrophotometers measure light absorption, refractometers measure refractive index, and calorimeters measure heat changes.
High porosity hair is characterized by which cuticle state?
Intact lipid layer
Smooth cuticle
Permanent closed cuticle
Raised cuticle scales
High porosity hair has lifted or raised cuticle scales, allowing moisture to enter and escape easily but also making hair prone to damage. Low porosity hair has smooth, flat cuticle layers.
What is the medulla in hair structure?
Outer protective layer
Type of protein bond
Growth phase of hair
Central core of the hair shaft
The medulla is the innermost layer of the hair shaft, often present in coarse hair and absent in finer hair. It plays a minor role in hair strength and structure. The cuticle is the outer layer, not the medulla.
Which amino acid is least abundant in hair keratin?
Lysine
Alanine
Cysteine
Glycine
Hair keratin is rich in cysteine, glycine, and alanine, but contains relatively low amounts of lysine. The high cysteine content forms many disulfide bonds crucial for hair strength.
Which test measures hair moisture regain?
pH measurement
Karl Fischer titration
Spectrophotometry
Tensile strength test
Karl Fischer titration is a chemical method to accurately determine water content in hair, measuring moisture regain. Tensile tests measure strength, spectrophotometry measures color, and pH meters measure acidity.
Which bond in hair is least affected by water immersion?
Van der Waals forces
Disulfide bond
Salt bond
Hydrogen bond
Disulfide bonds are covalent and stable in water, maintaining hair's shape under hydration. Hydrogen and salt bonds are weaker ionic or polar interactions that break in water.
Hair that absorbs moisture very slowly indicates which porosity level?
Low porosity
Variable porosity
High porosity
Medium porosity
Low porosity hair has tightly bound cuticle layers that resist moisture entry, so water absorption is slow. High porosity hair readily soaks up moisture. Variable porosity combines both traits.
Trichorrhexis nodosa describes which hair condition?
Fragility with nodes that break easily
Hair follicle inflammation
Excessive hair curling
Hair split ends
Trichorrhexis nodosa is characterized by weak points or nodes along the hair shaft where breakage occurs. It's not split ends or follicle inflammation, but structural damage within the shaft.
Which oil is known to penetrate the hair shaft most effectively?
Argan oil
Mineral oil
Coconut oil
Olive oil
Coconut oil has low molecular weight and good affinity for hair proteins, allowing it to penetrate the shaft. Olive, mineral, and argan oils mainly coat the surface.
What is the name of the scale-like pattern on hair cuticles?
Spinous
Coronate
Imbricate
Papillate
Human hair cuticles exhibit an imbricate (flattened, overlapping) scale pattern. Coronate and spinous patterns occur in other species, and papillate is not a standard term for scale patterns.
Which type of melanin is most abundant in red hair?
Pheomelanin
Allomelanin
Neuromelanin
Eumelanin
Pheomelanin imparts red and yellow tones and is dominant in red-haired individuals. Eumelanin produces brown to black colors. Neuromelanin and allomelanin are unrelated pigments.
An acidic treatment with a pH below what value helps close the hair cuticle?
6.5
4
5.5
7
Acidic formulations below pH 4 help tighten and close the cuticle scales, reducing frizz and improving shine. Neutral pH (7) and above can lift the cuticle.
What unit is commonly used to measure hair tensile strength?
Newton-meter (N·m)
Megapascal (MPa)
Mole (mol)
Candela (cd)
Tensile strength of hair is measured in stress units such as megapascals (MPa). Newton-meters measure torque, candela measures luminous intensity, and mole measures amount of substance.
Which mechanical test counts the percentage of hairs in the telogen phase?
Spectrometer
Porosimeter
Trichogram
Tensiometer
A trichogram involves plucking hairs and analyzing root bulbs to determine growth phase distribution, including telogen percentage. Tensiometers measure force, porosimeters assess porosity, and spectrometers measure light spectra.
Approximately how fast does human scalp hair grow per month?
1 cm per month
3 cm per month
0.1 cm per month
5 cm per month
Human scalp hair grows about 1 centimeter per month on average, or roughly 0.3 - 0.4 mm per day. Growth rates vary by individual and health factors.
Monilethrix is characterized by which feature?
Oil gland hyperactivity
Total alopecia
Excessive curling
Beaded appearance of the hair shaft
Monilethrix causes periodic narrowing along the hair shaft, producing a beaded appearance and fragility at constricted nodes. It does not cause complete hair loss or oil hyperactivity.
Which microscope provides detailed images of the hair surface?
Scanning electron microscope
Transmission electron microscope
Fluorescence microscope
Light microscope
A scanning electron microscope (SEM) uses electron beams to scan the hair surface, producing high-resolution topographical images. Transmission electron microscopes image internal structure, and light/fluorescence microscopes have lower resolution.
Which hydrophobic amino acid contributes most to hair keratin stability?
Serine
Aspartic acid
Lysine
Leucine
Leucine is a nonpolar, hydrophobic amino acid abundant in keratin, contributing to protein core stability via hydrophobic interactions. Serine and aspartic acid are polar/charged, and lysine is basic, not hydrophobic.
Which instrument is used to measure hair tensile strength in research?
Gas chromatograph
Atomic absorption spectrometer
Bomb calorimeter
Instron machine
An Instron universal testing machine measures force and elongation to determine tensile strength of hair fibers. Gas chromatography analyzes compounds, atomic absorption measures elements, and calorimeters measure heat.
What is the approximate isoelectric point (pI) of hair keratin?
2.0
9.5
4.5
7.0
The isoelectric point of hair keratin is around pH 4.5, where net charge is zero, influencing solubility and interactions. At pH 7 keratin carries negative charge.
Which hair type often lacks a medulla?
Dead hair fibers
Coarse terminal hair
All hair types
Fine vellus hair
Vellus hair is fine and often lacks a central medulla, unlike thicker terminal hair. Dead fibers still retain structure, and not all hair types universally lack medulla.
Which reducing agent cleaves disulfide bonds in hair?
Ethanol
Thioglycolic acid
Hydrochloric acid
Sodium hydroxide
Thioglycolic acid reduces disulfide bonds in keratin during processes like chemical relaxing or perming. Strong acids/bases and alcohol do not specifically cleave disulfide bridges.
Why are hydrolyzed keratin fragments used in protein treatments?
They increase scalp oil production
They can penetrate the hair shaft more easily
They permanently bond to DNA
They bleach hair pigments
Hydrolyzed keratin has smaller peptides that penetrate cuticle layers to reinforce cortex structure. They do not affect scalp oil production, DNA, or bleach pigments.
What does moisture regain of ~13% at 65% humidity indicate about hair?
Hair pH is 13
Hair binds about 13% of its dry weight in water
Hair loses 13% weight in water
Hair has 13% protein content
Moisture regain is the percentage of water hair reabsorbs at a set humidity. At 65% RH, hair typically regains about 13% of its dry weight. It's not about weight loss, protein, or pH.
Which tensile strength value is typical for a single hair fiber?
1 Pa
200 MPa
10 kPa
0.5 MPa
Tensile strength of a single hair fiber is on the order of 200 megapascals (MPa), similar to high-grade plastics. Values like 1 Pa or 10 kPa are far too low.
Which instrument images internal hair structure rather than surface?
Polarimeter
Scanning electron microscope
Chromatograph
Transmission electron microscope
Transmission electron microscopes (TEM) transmit electrons through thin hair slices, revealing internal structures. SEM scans the surface. Polarimeters measure optical rotation; chromatographs separate mixtures.
What is the average hair density on the human scalp per square centimeter?
500 hairs/cm²
200 hairs/cm²
50 hairs/cm²
1000 hairs/cm²
Average hair density is about 200 hairs per square centimeter on the scalp, varying with ethnicity and age. Values like 50 or 500 are too low or too high for population averages.
Which mechanical property measures hair stiffness?
Modulus of elasticity
Surface tension
Thermal conductivity
Viscosity
The modulus of elasticity quantifies stiffness by measuring stress/strain relationship. Viscosity relates to flow, thermal conductivity to heat transfer, and surface tension to liquid surfaces.
Which chemical treatment modifies hair disulfide bonds to reshape hair?
Henna dye
UV protectant spray
Silicone serum
Perm solution
Perm solutions break and reform disulfide bonds to create curls or waves. Henna dyes coat the shaft; silicones and protectants do not alter sulfur bonds.
At what pH do hair cuticles begin to lift, increasing permeability?
At pH 6
Exactly pH 5
Below pH 3
Above pH 7
Alkaline conditions above pH 7 cause cuticle scales to lift and increase hair permeability. Acidic pH below 5 helps close the cuticle.
What defines the primary structure of hair keratin?
Tertiary interactions
Beta-sheet formation
Helical folding
Amino acid sequence
Primary structure is the linear sequence of amino acids. Secondary structure includes alpha helices and beta sheets, tertiary involves 3D folding, and quaternary involves multi-chain assembly.
What molecular mechanism leads to trichoptilosis (split ends)?
High disulfide bond density
Excessive melanin under stress
Damage to cuticle exposes cortex to splitting
Overproduction of sebum
When cuticle scales are eroded, the underlying cortex is exposed and prone to longitudinal splitting, resulting in trichoptilosis. Melanin, sebum, and bond density are not direct causes of split ends.
How does water content influence hair's dielectric properties?
Moisture has no effect
Permittivity depends only on protein
Higher moisture increases permittivity
Dry hair has higher permittivity
Water is a polar molecule, so increased hair moisture raises dielectric permittivity by allowing greater charge polarization. Dry hair has lower permittivity. Protein alone does not dictate dielectric behavior.
Which spectroscopic method identifies functional groups in hair keratin?
X-ray crystallography
Mass spectrometry
FTIR spectroscopy
NMR imaging
Fourier-transform infrared (FTIR) spectroscopy detects characteristic vibrational bands of functional groups in keratin. NMR provides structural details in solution, mass spectrometry gives mass data, and X-ray crystallography reveals crystalline structures.
In finite element modeling of hair, what property is essential for deformation simulations?
Magnetic susceptibility
Acoustic impedance
Optical density
Elastic modulus
The elastic modulus defines the hair's stiffness and is crucial for simulating mechanical deformation in finite element models. Magnetic, optical, and acoustic properties are used in other analyses.
What role do melanin granules play in ultrasound attenuation in hair?
They convert ultrasound to heat
They amplify ultrasound signals
They have no effect
They scatter and absorb ultrasound waves
Melanin granules have acoustic impedance differences causing scattering and absorption of ultrasound waves. They do not amplify signals or solely convert energy to heat.
Which advanced technique analyzes keratin crystallinity in hair fibers?
X-ray diffraction
Thermogravimetric analysis
UV - Vis spectroscopy
Gas chromatography
X-ray diffraction measures spacing between crystalline regions in keratin, revealing its crystalline structure. UV - Vis spectroscopy measures light absorption, gas chromatography separates chemicals, and TGA measures thermal stability.
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Study Outcomes

  1. Understand Hair Protein Composition -

    Gain insight into why hair is approximately 90 percent protein and how keratin contributes to hair's strength and resilience.

  2. Define Trichoptilosis -

    Learn that trichoptilosis is the technical term for split ends and explore the factors that cause this common hair condition.

  3. Identify Vellus Hair Characteristics -

    Recognize that vellus hair almost never has a medulla and distinguish it from other hair types on the body.

  4. Analyze Hair Porosity -

    Explore which of the following statements best describes hair porosity to determine how moisture is absorbed and retained by hair strands.

  5. Apply Quiz Insights -

    Use your quiz results to reinforce key hair and scalp concepts, ensuring you can confidently discuss protein content, porosity, and hair disorders.

Cheat Sheet

  1. Protein Composition (90% Protein) -

    Hair is approximately 90 percent protein by weight, primarily keratin, a fibrous structural protein responsible for strength and elasticity. To remember keratin's role, use the mnemonic "Keep Every Root Anchored Through Intense Nourishment."

  2. Trichoptilosis (Split Ends) -

    Trichoptilosis is the technical term for split ends, derived from the Greek tricho "hair" and ptilosis "splitting." Frequent heat styling and mechanical stress weaken the cuticle, leading to these frayed tips.

  3. Hair Porosity Explained -

    Which of the following statements best describes hair porosity? It measures the hair's ability to absorb and retain moisture; high-porosity hair absorbs water quickly but loses it just as fast, while low-porosity hair resists water uptake. A simple float test - dropping a strand into water - helps classify porosity level.

  4. Vellus Hair Characteristics -

    Vellus hair almost never has a medulla, the central core found in thicker terminal hairs, making it fine and lightly pigmented. It covers most body areas (except palms and soles) and plays a role in temperature regulation.

  5. Hair Growth Cycle Phases -

    The three main phases - anagen (growth), catagen (transition), and telogen (rest) - govern hair renewal, with about 90% of scalp follicles in anagen at any given time. Remember the sequence with the acronym "A-C-T" (Anagen - Catagen - Telogen).

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