Biology: Energy, Cellular Processes, and Chromosomal Inheritance

Comprehensive practice flashcards covering cellular energetics (photosynthesis, cellular respiration, and fermentation) and genetic inheritance mechanisms (cell division, mitosis, meiosis, chromosomal abnormalities, and non-Mendelian inheritance).

How is energy defined in physics and biology, and what formula calculates work?

Energy is defined as the capacity to do work. Work is calculated using the formula: $\text{Work} = \text{Force} \times \text{Distance moved}$.

What is the primary difference between potential energy and kinetic energy?

Potential energy is the energy an object possesses due to its location or structure, whereas kinetic energy is the energy of motion.

What does the principle of conservation of energy state?

It states that energy can be converted from one form to another, but it cannot be created or destroyed.

What unusable form of energy is released as a by-product during every biological energy conversion?

At each energy conversion, some energy is lost to living things in the form of heat.

How do producers differ from consumers in how they acquire chemical energy?

Producers absorb solar energy from the sun and convert it into chemical energy (sugars) to make their own food, whereas consumers obtain energy by eating producers or other organisms.

In the internal anatomy of a chloroplast, what are thylakoids, grana, and stroma?

Thylakoids are individual membrane-bound disks, grana (singular: granum) are stacks of thylakoids, and the stroma is the fluid within the chloroplast inner membrane.

What is the overall balanced chemical reaction for photosynthesis?

The reaction is: $6\text{CO}_2 + 6\text{H}_2\text{O} + \text{Light Energy} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$.

What are the two linked stages of photosynthesis and their specific locations within the chloroplast?

The light reactions occur within the thylakoid membranes, and the Calvin cycle occurs in the surrounding stroma.

What roles do ATP and NADPH play in linking the two stages of photosynthesis?

ATP shuttles chemical energy and NADPH shuttles high-energy electrons from the light reactions to the Calvin cycle.

What happens to the water molecule ($\text{H}_2\text{O}$) absorbed by plants during the light reactions of photosynthesis?

Water is split to serve as an electron source for the light reactions, leaving oxygen gas ($\text{O}_2$) to be released as a by-product that exits the leaf.

What are the chemical inputs and primary product of the Calvin cycle?

The inputs are high-energy molecules from the light reactions (ATP and NADPH) and carbon dioxide ($\text{CO}_2$) taken in from the air via stomata; the primary product is sugar ($\text{C}_6\text{H}_{12}\text{O}_6$).

Which groups of living organisms carry out cellular respiration?

All living organisms—both producers and consumers—must use cellular respiration to harvest energy stored in sugars.

What gas is required for aerobic cellular respiration, and inside which organelle does it occur?

Aerobic respiration strictly requires oxygen ($\text{O}_2$) and takes place inside the mitochondria.

What is the true measurement of a dietary 'Calorie' (capital C) found on food nutrition labels?

A food Calorie is a kilocalorie ($\text{kcal}$), which equals $1{,}000$ scientific calories of chemical energy stored in food.

What are the three stages of cellular respiration, and which produces the vast majority of ATP?

The three stages are: 1. Glycolysis (cytoplasm), 2. Citric acid cycle (mitochondrial fluid), and 3. Electron transport chain (mitochondrial inner membrane). The electron transport chain produces the most ATP by far.

What is the overall chemical equation for cellular respiration?

The reaction is: $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{Chemical Energy for work (ATP)}$.

What events take place during glycolysis in cellular respiration?

Glycolysis occurs in the cytoplasm, splitting one molecule of glucose ($\text{C}_6\text{H}_{12}\text{O}_6$) into two molecules of pyruvic acid while producing a small amount of ATP and high-energy electrons carried by NADH.

What occurs during the citric acid cycle of cellular respiration?

Occurring in the fluid within mitochondria, it completes the breakdown of glucose by converting pyruvic acid into $\text{CO}_2$ (exhaled), yielding a small amount of ATP and high-energy electrons carried by NADH and $\text{FADH}_2$.

What is the role of oxygen in the mitochondrial electron transport chain?

Oxygen ($\text{O}_2$) serves as the final electron acceptor at the end of the electron transport chain, combining with electrons and hydrogen to form water ($\text{H}_2\text{O}$).

Under what condition does lactic acid fermentation occur in human muscles, and what does it yield?

Lactic acid fermentation occurs in muscle cells as an emergency anaerobic pathway when oxygen ($\text{O}_2$) is unavailable, yielding lactic acid and a small amount of ATP.

What substances are generated by yeast cells during anaerobic alcohol fermentation?

Yeast cells ferment sugars in anaerobic environments to produce carbon dioxide ($\text{CO}_2$), alcohol (ethanol), and a small bit of ATP.

How does cellular respiration serve as a metabolic hub for food molecules other than glucose?

In addition to sugars, the body can process carbohydrates into glucose, fats into fatty acids, and proteins into amino acids, all of which enter glycolysis or the citric acid cycle to generate ATP.

What is the biological definition of metabolism?

Metabolism is the sum total of all the chemical reactions that occur within an organism's body.

What are the two foundational claims of the cell theory?

The cell theory states that: 1. All life is cellular. 2. All cells arise from preexisting cells.

What three major biological functions does cell division support?

Cell division provides for organismal growth, tissue repair/replacement, and reproduction.

How do sexual and asexual reproduction contrast across parent numbers, gametes, fertilization, chromosome sets, and offspring variation?

Sexual reproduction requires $2$ parents, uses gametes, involves fertilization, gives offspring $2$ sets of chromosomes, and produces genetically unique offspring. Asexual reproduction requires $1$ parent, involves no gametes or fertilization, gives offspring $1$ set of chromosomes, and produces genetically identical clones.

What percentage of DNA is identical between two humans of the same sex, and how much accounts for unique traits?

Approximately $99.5\%$ of DNA is identical between two humans of the same sex, leaving only $0.5\%$ to account for all individual unique traits.

What is a gene, and what biological products does it encode?

A gene is a length of DNA (a small segment of a chromosome) containing the information needed to build one or more strands of protein or one or more molecules of RNA.

What is chromatin, and what is its typical physical state during non-dividing periods?

Chromatin is the combination of chromosomal DNA wound around proteins inside the nucleus; most of the time it remains unraveled as loose fibers.

What are sister chromatids, and where are they joined together?

Sister chromatids are duplicated, identical copies of a chromosome that are joined together at a narrow region called the centromere.

What are the two broad phases of the eukaryotic cell cycle, and how much time is spent in the non-dividing phase?

The cell cycle consists of Interphase and the Mitotic phase. A cell spends approximately $90\%$ of its lifetime in Interphase carrying out normal cellular functions.

What key cellular events take place during interphase?

During interphase, the cell performs its normal functions, grows in size, and prepares for division by duplicating its chromosomes.

What are the four sequential stages of mitosis and the defining event of each?

1. Prophase: Chromosomes condense, the nuclear membrane dissolves, and the mitotic spindle forms. 2. Metaphase: Chromosomes align along the cell equator. 3. Anaphase: Sister chromatids split and are pulled to opposite poles. 4. Telophase: Two nuclear membranes re-form around the separated chromosomes.

How does the mechanism of cytokinesis differ between dividing animal cells and dividing plant cells?

Animal cells divide by constricting the cytoplasm through a cleavage furrow, whereas plant cells divide by building a cell plate along the center line that develops into a new cell wall.

How does reproductive cloning differ from therapeutic cloning?

In reproductive cloning, an embryo produced via nuclear transplantation is implanted into a surrogate mother to birth a cloned organism; in therapeutic cloning, stem cells are harvested from the embryo to generate specific tissue types.

What is the procedure for nuclear transplantation in cloning mammals?

The nucleus is removed from an unfertilized donor egg cell, and the nucleus isolated from an adult cell of the individual to be cloned is injected into that nucleus-free egg.

What are the ploidy numbers and chromosome counts of human gametes compared to human somatic cells?

Gametes (sperm and egg) are haploid ($n$) and contain $23$ chromosomes, while somatic body cells are diploid ($2n$) and contain $46$ chromosomes ($23$ pairs).

How many autosomes and how many sex chromosomes are found in each typical human body cell?

Each human body cell contains $44$ autosomes ($22$ pairs) and $2$ sex chromosomes ($1$ pair: $\text{XX}$ in females or $\text{XY}$ in males).

How do meiosis and mitosis differ in terms of site of occurrence, timing, number/type of daughter cells, and rounds of division?

Meiosis occurs only in ovaries/testes starting at puberty, involves $2$ rounds of division, and produces $4$ haploid gametes. Mitosis occurs in all body cells across a lifetime, involves $1$ round of division, and produces $2$ diploid cells.

What three major biological mechanisms generate genetic diversity in sexually reproducing organisms?

1. Independent assortment of chromosomes. 2. Random fertilization of gametes. 3. Crossing over during meiosis I.

How many possible chromosome combinations can arise in human gametes through independent assortment alone?

Independent assortment yields approximately $8\text{ million}$ ($2^{23}$) possible combinations of maternal and paternal chromosomes.

How many unique chromosome combinations can result in a human zygote from random fertilization?

Random fertilization yields approximately $64\text{ trillion}$ possible combinations ($8\text{ million} \times 8\text{ million} = 64\text{ trillion}$).

What occurs during crossing over in meiosis I, and what is its genetic outcome?

Homologous chromosomes line up and swap corresponding segments of DNA, producing new hybrid (recombinant) chromosomes carrying novel gene combinations.

What is nondisjunction, and what chromosome numbers result in affected gametes?

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during meiosis, producing abnormal gametes with $n + 1 = 24$ or $n - 1 = 22$ chromosomes.

What chromosomal abnormality causes Down syndrome, and how does it appear on a karyotype?

Down syndrome is caused by Trisomy 21, resulting in a complete set of $47$ chromosomes characterized by three copies of chromosome 21.

What sex chromosome genotypes and clinical phenotypes characterize Triple-X, Jacob's, Klinefelter, and Turner syndromes?

Triple-X ($\text{XXX}$, female: slightly taller, mild learning delay risk); Jacob's ($\text{XYY}$, male: normal, slightly taller); Klinefelter ($\text{XXY}$, male: sterile, underdeveloped testes, feminine traits); Turner ($\text{XO}$, female: sterile, immature sex organs; sole known viable 45-chromosome human condition).

What is the distinction between a character and a trait in genetics?

A character is an inherited feature that varies among individuals (such as eye color), whereas a trait is each specific variant of that character (such as green, brown, or blue eyes).

What is the difference between an organism's genotype and its phenotype?

Phenotype is an organism's observable physical traits, while genotype is its underlying genetic makeup (the specific alleles it carries).

What does Mendel's law of segregation state regarding alleles?

It states that the two alleles for a character separate during gamete formation, so each gamete carries only one allele for each gene.

In a monohybrid cross between two heterozygous black Labrador retrievers ($Bb \times Bb$), what are the expected genotypic and phenotypic ratios?

The genotypic ratio is $1\,BB : 2\,Bb : 1\,bb$. The phenotypic ratio is $3\text{ black dogs} : 1\text{ chocolate dog}$.

How does a genetic test cross reveal whether an individual showing a dominant phenotype is homozygous ($BB$) or heterozygous ($Bb$)?

The individual is mated with a homozygous recessive individual ($bb$). If all offspring display the dominant trait, the parent is $BB$; if any offspring display the recessive trait ($1:1$ ratio), the parent is $Bb$.

What does Mendel's law of independent assortment state, and what phenotypic ratio results from a dihybrid cross ($BbDd \times BbDd$)?

It states that the inheritance of one character has no effect on the inheritance of another. A dihybrid cross between heterozygous parents produces a $9:3:3:1$ phenotypic ratio.

What is incomplete dominance, and what phenotypic ratio is produced when crossing two pink snapdragons ($Rr \times Rr$)?

Incomplete dominance occurs when heterozygotes exhibit an intermediate phenotype; crossing two pink ($Rr$) snapdragons produces $1\text{ red } (RR) : 2\text{ pink } (Rr) : 1\text{ white } (rr)$.

What are the three alleles that determine human ABO blood types, and which alleles demonstrate codominance?

The alleles are $i$, $I^A$, and $I^B$. Alleles $I^A$ and $I^B$ are codominant (both are expressed simultaneously in genotype $I^A I^B$, creating type AB blood), and both are dominant over recessive allele $i$.

What is pleiotropy, and how does sickle-cell disease illustrate it?

Pleiotropy occurs when a single gene influences multiple distinct physical characters. The sickle-cell mutation causes red blood cells to deform, triggering anemia, physical weakness, pain, and extensive organ damage.

What is polygenic inheritance, and what are two prominent human examples?

Polygenic inheritance is the additive effect of multiple genes on a single phenotypic character, resulting in a continuous spectrum of variation such as human height and skin color.

Why do linked genes violate Mendel's law of independent assortment, and how does physical proximity affect crossing over?

Linked genes are located close together on the same chromosome and tend to be inherited together. Genes located closer together have a much lower probability of being separated by a crossover event.

Why are sex-linked recessive conditions such as hemophilia expressed far more frequently in males than in females?

Males have only one X chromosome ($\text{XY}$); if they inherit a single recessive disease allele on their maternal X chromosome, they develop the disorder, whereas females ($\text{XX}$) require two copies to express it.