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OpenStem
@openstem · Joined Jul 2026
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Flashcards9 cards
What is the difference between mechanical and chemical digestion?1 / 9
Mechanical digestion physically breaks food into smaller pieces (chewing, churning) without changing its chemical structure. Chemical digestion uses enzymes to break chemical bonds, converting large molecules into smaller absorbable units.
Biology · L3 · Mechanical, Chemical Digestion, and Absorption
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Biology · L3 · Mechanical, Chemical Digestion, and AbsorptionFlashcards10 cards
What is a neuron?1 / 10
A neuron is a nerve cell specialised to carry electrical signals, called nerve impulses, through the body. Neurons are the basic building blocks of the nervous system.
Biology · L3 · Neuron Structure and the Action Potential
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Biology · L3 · Neuron Structure and the Action PotentialFlashcards10 cards
What does CNS stand for, and what does it include?1 / 10
CNS stands for central nervous system. It includes the brain and the spinal cord, the body's main processing and control centres.
Biology · L3 · CNS, PNS, and the Reflex Arc
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Biology · L3 · CNS, PNS, and the Reflex ArcFlashcards10 cards
What is innate immunity?1 / 10
Innate immunity is the set of defenses you are born with. It responds the same way to any pathogen, acts within minutes to hours, and does not require prior exposure to the invader.
Biology · L3 · Innate Immunity
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Biology · L3 · Innate ImmunityFlashcards10 cards
What is adaptive immunity, and how is it different from innate immunity?1 / 10
Adaptive immunity is a slower, highly specific defense that targets a particular pathogen. Unlike innate immunity, it improves with repeated exposure and creates lasting memory of the invader.
Biology · L3 · Adaptive Immunity
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Biology · L3 · Adaptive ImmunityFlashcards10 cards
Why is the pituitary gland often called the "master gland"?1 / 10
Because it secretes hormones that regulate the activity of several other endocrine glands, including the thyroid and adrenal glands. The pituitary itself is controlled by the hypothalamus, which sits just above it.
Biology · L3 · Glands and Hormones
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Biology · L3 · Glands and HormonesFlashcards10 cards
What is a negative feedback loop, in the context of the endocrine system?1 / 10
A control mechanism in which rising levels of a hormone (or the product it causes) inhibit further release of that hormone, or of the signals that triggered it. This keeps hormone levels within a stable, healthy range and is the basis of most endocrine regulation.
Biology · L3 · Hormone Action and Feedback
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Biology · L3 · Hormone Action and FeedbackFlashcards10 cards
What are the two main types of bone tissue in the human skeleton?1 / 10
Biology · L3 · Bone Structure and Types
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Biology · L3 · Bone Structure and TypesFlashcards10 cards
What is a joint (articulation)?1 / 10
A joint is the point where two or more bones meet. Joints are classified both by the type of tissue connecting the bones and by how much movement they allow.
Biology · L3 · Joints and Skeletal Functions
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Biology · L3 · Joints and Skeletal FunctionsFlashcards10 cards
What are the three types of muscle tissue in the human body?1 / 10
Skeletal muscle, smooth muscle, and cardiac muscle. Each has a distinct microscopic structure suited to its role.
Biology · L3 · The Three Types of Muscle Tissue
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Biology · L3 · The Three Types of Muscle TissueFlashcards10 cards
What is a sarcomere?1 / 10
The basic contractile unit of a skeletal muscle fiber, repeated end to end along a myofibril. Each sarcomere is bounded by two Z-discs and contains organized, overlapping actin and myosin filaments.
Biology · L3 · How Skeletal Muscle Contracts
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Biology · L3 · How Skeletal Muscle ContractsFlashcards10 cards
What is the main function of the kidneys?1 / 10
The kidneys filter waste products, excess water, and excess ions out of the blood, producing urine, while also helping regulate blood pressure, blood volume, and the body's ion balance.
Biology · L3 · Kidney and Nephron Structure
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Biology · L3 · Kidney and Nephron StructureFlashcards9 cards
What are the three main processes involved in forming urine?1 / 9
Urine forms through filtration, reabsorption, and secretion, which together determine which substances leave the blood permanently as waste and which are returned to circulation.
Biology · L3 · Urine Formation and Water Regulation
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Biology · L3 · Urine Formation and Water RegulationFlashcards10 cards
What is meiosis, and why is it essential for sexual reproduction?1 / 10
Meiosis is a type of cell division that produces four genetically distinct daughter cells, each with half the chromosome number of the parent cell. It reduces the chromosome number so that when two gametes fuse during fertilization, the resulting cell has the normal, complete chromosome number.
Biology · L3 · Gametogenesis and Reproductive Hormones
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Biology · L3 · Gametogenesis and Reproductive HormonesFlashcards10 cards
What is the bacterial cell wall made of, and what is its function?1 / 10
The bacterial cell wall is made of peptidoglycan, a mesh-like polymer of sugar chains cross-linked by short amino acid bridges. It sits outside the cell membrane, gives the cell its shape, and prevents it from bursting when water enters by osmosis.
Biology · L3 · Bacterial Structure and Classification
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Biology · L3 · Bacterial Structure and ClassificationFlashcards10 cards
What is a virus, and why is it usually described as non-living?1 / 10
A virus is an infectious particle made of genetic material (DNA or RNA) enclosed in a protein coat. It is usually considered non-living because it has no cytoplasm, ribosomes, or metabolism of its own, and cannot reproduce without hijacking the machinery of a living host cell.
Biology · L3 · Viruses and Infection
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Biology · L3 · Viruses and InfectionFlashcards10 cards
What is a chloroplast, and what pigment gives it its color?1 / 10
A chloroplast is a double-membraned organelle in plant cells where photosynthesis takes place. It contains chlorophyll, a green pigment that absorbs light energy, mainly in the red and blue wavelengths, while reflecting green light.
Biology · L3 · Photosynthesis in Depth
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Biology · L3 · Photosynthesis in DepthFlashcards10 cards
What does xylem transport, and in which direction does it move?1 / 10
Xylem transports water and dissolved mineral ions from the roots upward to the stems and leaves. Movement is one-directional, driven mainly by transpiration pulling water up through dead, hollow xylem cells.
Biology · L3 · Plant Transport and Hormones
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Biology · L3 · Plant Transport and HormonesFlashcards10 cards
What is carrying capacity?1 / 10
The maximum population size of a species that an environment can sustain indefinitely, given the available food, water, space, and other resources. Populations tend to level off near this value rather than growing without limit.
Biology · L3 · Population and Community Ecology
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Biology · L3 · Population and Community EcologyFlashcards10 cards
What is a trophic level?1 / 10
A feeding position in a food chain or food web, defined by how many energy transfers separate an organism from the original energy source (usually the sun). Producers occupy the first trophic level, followed by primary consumers, secondary consumers, and so on.
Biology · L3 · Energy Flow and Nutrient Cycling
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Biology · L3 · Energy Flow and Nutrient CyclingFlashcards10 cards
What is taxonomy?1 / 10
The branch of biology concerned with identifying, naming, and classifying organisms into a nested system of groups based on shared characteristics and evolutionary relationships.
Biology · L3 · The Taxonomic Hierarchy and Binomial Nomenclature
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Biology · L3 · The Taxonomic Hierarchy and Binomial NomenclatureFlashcards10 cards
What are the three domains of life?1 / 10
Biology · L3 · The Three Domains and Phylogenetic Trees
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Biology · L3 · The Three Domains and Phylogenetic TreesFlashcards10 cards
What is a monomer, and what is a polymer?1 / 10
A monomer is a small, repeating molecular subunit. A polymer is a large molecule built by joining many monomers together in a chain. Three of the four major biological macromolecules — carbohydrates, proteins, and nucleic acids — are polymers built from their own characteristic monomers; lipids are the exception, since they are not true polymers.
Biology · L3 · The Four Macromolecules
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Biology · L3 · The Four MacromoleculesFlashcards10 cards
What is an enzyme, and what is its general chemical identity?1 / 10
An enzyme is a biological catalyst — a substance that speeds up a chemical reaction without being consumed or permanently changed by it. Almost all enzymes are proteins, and their three-dimensional shape, determined by how the polypeptide chain folds, is essential to how they work.
Biology · L3 · Enzymes and Enzyme Activity
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Biology · L3 · Enzymes and Enzyme ActivityFlashcards10 cards
What is cellular respiration, in one sentence?1 / 10
Cellular respiration is the process cells use to break down glucose and release its stored chemical energy as ATP, the molecule cells use to power almost everything they do.
Biology · L3 · Cellular Respiration Stages
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Biology · L3 · Cellular Respiration StagesFlashcards10 cards
What does 'aerobic' mean, and why does aerobic respiration make so much more ATP than anaerobic respiration?1 / 10
Aerobic means 'requiring oxygen.' With oxygen available, pyruvate can be fully processed through the Krebs cycle and the electron transport chain, which together generate far more ATP than glycolysis alone can produce.
Biology · L3 · Aerobic vs. Anaerobic Respiration and ATP Yield
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Biology · L3 · Aerobic vs. Anaerobic Respiration and ATP YieldFlashcards10 cards
What organ acts as the body's "thermostat" for temperature control?1 / 10
The hypothalamus, a small region at the base of the brain. It constantly monitors the temperature of the blood flowing through it and compares that reading to a set point of about 37°C, then triggers whatever response is needed to correct any difference.
Biology · L3 · The Body's Thermostat
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Biology · L3 · The Body's ThermostatFlashcards10 cards
Complete the pair: vasodilation is to cooling as vasoconstriction is to ___.1 / 10
Warming (heat conservation). Vasodilation widens skin blood vessels to lose heat when the body is too hot; vasoconstriction narrows them to keep heat in the core when the body is too cold. They are opposite responses controlled by the same hypothalamic thermostat.
Biology · L3 · Hot and Cold Responses Compared
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Biology · L3 · Hot and Cold Responses ComparedFlashcards10 cards
What are the three macronutrients, and what do they have in common?1 / 10
Carbohydrates, proteins, and fats. All three are nutrients the body needs in relatively large amounts, and all three can be broken down to release energy, measured in kilocalories (kcal).
Biology · L3 · Macronutrients and Energy
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Biology · L3 · Macronutrients and EnergyFlashcards10 cards
What is basal metabolic rate (BMR)?1 / 10
BMR is the rate at which the body uses energy at complete rest to keep essential functions running — such as breathing, circulating blood, and maintaining body temperature — without any physical activity or digestion.
Biology · L3 · Metabolism, BMR, and BMI
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Biology · L3 · Metabolism, BMR, and BMI