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Biology: explore STEM content (page 47 of 50) · openstem
Explore STEM Content
Search the community's STEM library — free to study, yours to make your own.
Biology
Cells, genetics, ecology and physiology on openstem — flashcards, notes, quizzes, sketches and flowcharts shared by the community. Study free, or clone anything into your library.
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.
What is transpiration, at the scale of a whole tree?1 / 8
Transpiration is the release of water vapor from a plant's leaves into the air, mostly through tiny pores called stomata. At the scale of a whole tree, it is a continuous, large-volume loss of water — not a trickle, but a flow measured in hundreds of liters a day for a large tree.
Proteomics and Mass Spectrometry Mass spectrometry-based proteomics identifies and quantifies proteins from complex biological mixtures by measuring the mass-to-charge ratio of ionized peptides or proteins. The dominant strategy, bottom-up
Asthma is a chronic condition in which the airways — mainly the bronchi and bronchioles — become inflamed and overly sensitive, periodically narrowing and making it harder for air to flow in and out of the lungs.
Explain the amyloid cascade hypothesis of Alzheimer disease, including the roles of APP processing, amyloid-beta aggregation, and downstream tau pathology.1 / 9
The amyloid cascade hypothesis proposes that accumulation of amyloid-beta peptide, generated by sequential cleavage of amyloid precursor protein (APP) by beta-secretase (BACE1) and then gamma-secretase (a complex including presenilin as the catalytic subunit), is the initiating event in Alzheimer disease pathogenesis; amyloid-beta42, the more aggregation-prone cleavage product, self-assembles into soluble oligomers and eventually insoluble extracellular plaques.
Describe the hypothalamic-pituitary-gonadal (HPG) axis and its major hormones.1 / 11
The hypothalamus secretes gonadotropin-releasing hormone (GnRH) in a pulsatile pattern, which stimulates the anterior pituitary to secrete the gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These gonadotropins act on the gonads (ovaries or testes), stimulating gametogenesis and secretion of the sex steroids (estrogen and progesterone in females, testosterone in males), which in turn feed back on the hypothalamus and pituitary to regulate further GnRH/FSH/LH release, forming a classic multi-tiered endocrine axis common to both sexes despite very different downstream physiology.
Biology
Biology · L4 · Reproductive Endocrinology and Gametogenesis
What is the nucleus, and what two roles does it play in a eukaryotic cell?1 / 9
The nucleus is the cell's control center. It stores the cell's DNA, organized with proteins into chromatin, and it directs gene expression — deciding which genes are switched on to produce which proteins. It is bounded by a double membrane called the nuclear envelope.
What is one medical application scientists are exploring with CRISPR?1 / 10
Potential treatments for genetic diseases — conditions caused by a faulty gene, such as sickle cell disease — by editing the gene responsible for the condition.
Central Tolerance Central tolerance purges the developing lymphocyte repertoire of high-avidity self-reactive clones within primary lymphoid organs, before those cells can traffic to the periphery. For T cells, this occurs during thymocyte
Biology
Biology · L5 · Immune Tolerance and Cytokine Signalling Networks
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.
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.
Predicting offspring with a Punnett square A Punnett square is a grid used to predict the possible genotypes and phenotypes of offspring from a genetic cross. Each parent's possible gametes are listed along one edge of the grid, and each ce
Biology
Biology · L3 · Genetics and Heredity: Reading a Punnett Square
A pattern in which two species exert reciprocal selection pressure on each other over many generations, so that an evolutionary change in one species favors a counter-change in the other. Neither species evolves in isolation — each is responding to the other.
Biology
Biology · L3 · Coevolution Basics and the Red Queen Hypothesis
How Insects and Small Creatures Survive Winter Winter is hard for small creatures. It is cold, and there are not many plants or flowers to eat. Insects and other small creatures have found clever ways to make it through until spring. Flying
Biology
Biology · L1 · How Insects and Small Creatures Survive Winter