Free NLN NEX Science Exam Flashcards

A prokaryote lacks a membrane-bound nucleus; its DNA occupies a nucleoid region. A eukaryote has a membrane-bound nucleus and other membrane-bound organelles. Both have DNA, ribosomes, cytoplasm and a plasma membrane.

Rough ER has attached ribosomes and helps produce and process many secreted or membrane proteins. Smooth ER participates in lipid synthesis and other functions. The Golgi modifies, sorts and packages material for delivery.

Many plant cells, including most root cells, do not photosynthesise and lack chloroplasts. A cellulose cell wall and other features can still identify a plant cell. Use several structural features rather than one missing organelle.

Proteins contain amino acids; DNA and RNA contain nucleotides; polysaccharides contain monosaccharides. Many common lipids contain glycerol and fatty acids, but lipids are not all repeating-unit polymers.

Water enters by osmosis, so the cell swells and may lyse if the difference is large enough. Tonicity depends on solutes that do not readily cross the membrane, not simply the total count of every dissolved particle.

Mitosis usually produces two daughter nuclei with the parent’s chromosome number. Meiosis has two divisions after one DNA replication and reduces diploid cells to haploid products. Human oogenesis does not produce four equally functional eggs.

Interphase. It contains 80 of 100 observed cells, or 80%. In a stable, asynchronous population, a larger share suggests more time spent in that phase. The counts are a model estimate, not direct timing of one cell.

Adenine pairs with thymine; guanine pairs with cytosine. DNA contains deoxyribose. RNA contains ribose and typically uses uracil instead of thymine. “DNA is always double-stranded” is too absolute across all biological entities.

Transcription makes an RNA copy from a DNA template. Translation uses a ribosome to read mRNA and assemble an amino-acid sequence. In eukaryotes, nuclear transcription and ribosomal translation occur in different cellular locations.

Genotypes: 1 AA : 2 Aa : 1 aa. Phenotypes: 3 dominant : 1 recessive. Each offspring has its own probabilities; four births need not contain exactly one AA, two Aa and one aa.

One-half. The son receives Y from his father and one of his mother’s X chromosomes. This is the probability conditional on being a son; the probability of an affected son among all children also depends on the probability of a male child.

Net yield is 2 ATP per glucose: 4 formed minus 2 invested. Glycolysis occurs in the cytosol and does not itself require oxygen. Oxygen is the final electron acceptor in aerobic electron transport, a different stage.

Light-dependent reactions occur in thylakoid membranes and generate ATP and NADPH while releasing oxygen from water. The Calvin cycle occurs in the stroma and uses these products to build carbohydrate precursors from carbon dioxide.

No. If inherited beak differences affected survival and reproduction, natural selection could change trait frequencies across generations. The environment selects among variation; it does not make each bird deliberately acquire the needed inherited trait.

Bacteria, Archaea and Eukarya. Domain is broader than kingdom. Classification reflects evolutionary relationships and can change with evidence; treating every organism as belonging to one fixed, universal five-kingdom scheme is misleading.

800 ÷ 10,000 × 100 = 8%. The familiar 10% transfer value is a rough teaching approximation, not a constant law. Energy is used in metabolism and transferred to the surroundings or other pathways.

Growth slows and approaches a plateau near 50 under the observed conditions. Resource limitation may be involved, but the table alone does not identify the limiting factor or prove that carrying capacity will stay at 50.

Random assignment helps distribute other differences between groups; comparable water reduces a competing explanation. Measure an outcome such as growth, include replication and change the intended exposure. A result supports an inference within the design’s limits.

Sagittal: left and right portions; midsagittal: equal left and right halves. Frontal: anterior and posterior portions. Transverse: superior and inferior portions. These descriptions use anatomical position, not the viewer’s position.

Right ventricle. Blood then passes through the pulmonary trunk and pulmonary arteries toward the lungs. The diagram describes the adult pulmonary route; oxygen-poor blood does not go directly from the right atrium to the left ventricle.

Trachea → bronchi → smaller bronchi → bronchioles → respiratory passages and alveoli. Most gas exchange occurs across thin alveolar–capillary surfaces. The epiglottis participates in coordinated swallowing; it is not the only airway-protection mechanism.

The brain and spinal cord form the central nervous system. Nerves and ganglia outside them belong to the peripheral nervous system. “Sensory” and “motor” describe functional pathways, not the same division as central versus peripheral.

The thyroid gland. The parathyroid glands usually lie on its posterior surface and have different hormone functions. Location plus structural description distinguishes these glands; the thyroid is not inside the brain or on top of a kidney.

Tendons attach muscle to bone; skeletal ligaments generally connect bone to bone across joints. The standard adult skeleton is often counted as 206 bones, but anatomical variation exists. “Ligament” also names some structures outside joints.

Cardiac muscle. Skeletal muscle is striated but usually has long, unbranched fibres; smooth muscle lacks visible striations. Cardiac muscle works involuntarily. These are typical tissue features rather than a diagnosis from one isolated sign.

Ileum. It follows the jejunum and joins the cecum at the ileocecal junction. The liver, gallbladder and pancreas are accessory digestive organs, not successive sections through which food normally passes.

A is a ureter; B is the urethra. The bladder stores urine, while the kidneys produce it. Ureters and urethra are different structures despite similar names; urine does not travel from the bladder back through a kidney in the normal route.

The uterine tube, most often its ampulla. The resulting early embryo normally travels toward the uterus and implants in the endometrium. The uterine cavity and vagina are not the usual sites of fertilisation.

Negative feedback opposes the initial deviation from a regulated range. Positive feedback amplifies a change, as in the oxytocin-driven part of labour, until a terminating event. “Negative” does not mean harmful and “positive” does not mean beneficial.

Cardiac output = heart rate × stroke volume. It changes from 4,900 mL/min (4.9 L/min) to 12,000 mL/min (12 L/min). These are provided examples, not universal values or diagnostic thresholds.

Into the lungs, down the pressure gradient. During quiet inspiration, diaphragm contraction helps increase thoracic volume. Expiration at rest is largely passive recoil; forced breathing recruits additional muscles.

Opening voltage-gated sodium channels commonly allows Na+ influx during rapid depolarisation. Increased K+ efflux contributes to repolarisation. Resting and threshold voltages vary by cell; −70 mV and −55 mV are teaching examples, not universal constants.

ADH is made by hypothalamic neurons, then transported to and released from the posterior pituitary. It increases water permeability in parts of the renal collecting system when appropriate receptors and channels respond. The posterior pituitary does not synthesise it.

Pancreatic beta cells release insulin, which promotes glucose uptake in responsive tissues and storage, including glycogen formation. Between meals, glucagon supports hepatic glucose output. This explains physiology, not a rule for selecting or dosing a medicine.

Reabsorption is limited by available transport mechanisms. Above capacity, some filtered glucose remains in the tubule and is excreted. Glucose in urine has several possible explanations; this principle does not diagnose a person or establish a universal blood-glucose threshold.

Bile emulsification increases accessible surface area for lipase, helping fat hydrolysis. Bile itself is not the digestive enzyme. The comparison supports this mechanism under the model’s conditions; it does not establish the cause of a patient’s symptoms.

Calcium binds troponin, helping move tropomyosin away from actin binding sites. ATP binding lets myosin detach; ATP hydrolysis helps reset it. Filaments slide past one another rather than each filament becoming shorter.

Adaptive immune memory. Memory B and T cells can respond more effectively on re-exposure. Protection varies by antigen and time; vaccination does not guarantee that infection or transmission can never occur.

Atomic number counts protons; mass number counts protons plus neutrons in one isotope. Isotopes of an element have different neutron counts. Ions have a net charge from unequal proton and electron counts; gaining electrons does not change the element.

A polar covalent bond shares electrons unequally. An ionic bond is electrostatic attraction between oppositely charged ions. Hydrogen bonds are weaker attractions involving suitable partially positive hydrogen and an electronegative partner; they can occur between or within molecules.

Pressure × volume stays at 200 kPa·L, matching Boyle’s law for an ideal-gas approximation at constant temperature and amount. These pressures are absolute, not gauge values. Changing temperature or gas amount need not preserve this relationship.

The pH 4 solution has about 100 times the hydrogen-ion concentration: 10^(6 − 4) = 100. Strictly, pH uses hydrogen-ion activity. A lower pH indicates greater acidity; it does not alone identify the acid or its total amount.

A catalyst provides a pathway with lower activation energy and speeds approach to equilibrium. It does not change the equilibrium constant or create a different equilibrium composition at the same temperature. Most enzymes are proteins, but catalytic RNA also exists.

Primary prevention aims to prevent onset; secondary prevention detects or treats disease early; tertiary prevention limits effects or disability from established disease. Screening is not itself proof of disease, and rehabilitation is not primary prevention.

Active immunity develops through the recipient’s own immune response, such as after vaccination. Passive immunity supplies preformed antibodies, such as maternal IgG. Passive protection is temporary and does not itself create the recipient’s immune memory.

Apply about 4 kcal/g for carbohydrate and protein and 9 kcal/g for fat: 10 × 4 + 5 × 4 + 2 × 9 = 78 kcal. These general factors are approximate; a label’s total can differ because of rounding, fibre and other components.

No. Prevent cross-contamination by separating raw poultry from ready-to-eat foods and cleaning hands, utensils and surfaces. Food can contain harmful microbes without visible spoilage. Do not use appearance, smell or taste as proof of safety.

Physical, mental, emotional, social and spiritual dimensions can all affect well-being. These dimensions interact, and people express spiritual well-being in different ways. Respect individual beliefs; one dimension or appearance cannot determine someone’s overall health.

It is a health condition involving problematic substance use and impaired control despite harmful consequences. Biological, psychological and social factors can contribute. Compassionate assessment and evidence-based support are appropriate; a stereotype does not diagnose or explain an individual.

No. Access barriers are a plausible explanation, and the association alone does not establish causation. Investigate transport, cost, scheduling and other factors. An avoidable, unfair access difference can represent a health inequity, not a personal failing.