VCE Biology: Cells, Membranes, Cell Division, and Key Science Skills

Comprehensive practice flashcards covering Key Science Skills and Bioethics, Cell Structure and Organelles, Plasma Membrane Transport, and the Cell Cycle, Mitosis, Apoptosis, and Stem Cells from VCE Biology Units 1 & 2.

What three core criteria must a scientific research question satisfy to be considered effective?

A research question must be testable (factors can be measured), achievable (the scientist possesses the required funding, ethical approval, and resources), and specific (focused on particular individuals, times, and locations).

How are independent, dependent, and controlled variables defined in a controlled experiment?

The independent variable ($\text{IV}$) is the factor deliberately manipulated by the experimenter. The dependent variable ($\text{DV}$) is the factor measured to see how it changes in response to the $\text{IV}$. Controlled variables are all other factors held constant throughout the investigation to prevent them from influencing the $\text{DV}$.

In an experiment investigating the effect of exercise levels on the occurrence of heart disease, how does age act as a confounding variable if left uncontrolled?

Age can influence a person's physical activity level and independently affects their risk of developing heart disease. If age is not kept constant, it acts as an uncontrolled extraneous factor, making it impossible to establish whether exercise alone influenced heart disease occurrence.

What is the distinction between a negative control group and a positive control group?

A negative control is not exposed to the experimental treatment and is expected to produce no response, verifying that no external variable is affecting the $\text{DV}$. A positive control is exposed to a treatment with a known, well-understood effect, verifying that the experimental setup and measurement tools function correctly.

Based on the bullseye diagrams, how do accuracy and precision differ in scientific investigations?

Accuracy describes how close a measured value is to the true value (the centre of the target). Precision describes how closely repeated measurements of the same quantity agree with one another (the tightness of the cluster), regardless of how close they are to the true value.

How do systematic errors and random errors differ in their cause, impact on data, and remediation?

Systematic errors cause results to differ from the true value by a consistent amount each time due to faulty equipment or calibration, reducing accuracy; they cannot be eliminated by replication and require instrument maintenance or recalibration. Random errors cause unpredictable variations between replicates due to uncontrollable conditions, reducing precision; their impact is minimised by increasing sample size and replication.

What are the key characteristics of systematic sampling and stratified sampling?

Systematic sampling takes samples at regular, fixed intervals along an environmental gradient (such as depth, altitude, or temperature). Stratified sampling divides a population with distinct zones or sub-groups into strata and samples proportionately from each zone.

What rules determine the numerical uncertainty for analogue measuring instruments that require physical setup versus those that do not?

For analogue instruments that must be physically positioned or aligned before measuring (such as a ruler), the uncertainty equals the smallest scale increment ($\pm 1\,\text{mm}$). For analogue instruments that do not require positioning before measuring (such as a measuring cylinder or thermometer), the uncertainty equals half of the smallest increment ($\pm 0.5\,\text{mL}$).

How do consequences-based, duty/rule-based, and virtues-based approaches to bioethics guide moral decision-making?

A consequences-based approach aims to maximise positive outcomes and minimise negative outcomes. A duty/rule-based approach prioritises fulfilling duties, responsibilities, and rules regardless of the consequences. A virtues-based approach emphasizes the moral character of the agent, acting in accordance with what a good, compassionate, and moral person would do.

What are the core commitments of the five bioethical concepts: integrity, justice, beneficence, non-maleficence, and respect?

Integrity commits to honest reporting of all facts and results; justice commits to fair distribution of benefits, burdens, and equal access; beneficence commits to maximising benefits for others; non-maleficence commits to minimising harm; and respect commits to acknowledging individual autonomy, intrinsic value, and cultural beliefs.

What eight criteria must an entity fulfil to be classified as a living organism according to the MRS GREEN mnemonic?

The eight criteria are: Movement (self-generated motion), Respiration (biochemical extraction of cellular energy), Sensitivity (sensing and responding to stimuli), Growth (growing and developing over time), Reproduction (producing new organisms), Equilibrium (maintaining homeostasis), Excretion (removing metabolic wastes), and Nutrition (extracting nutrients from the environment).

What are the three core principles of classical cell theory?

1. All living organisms are composed of one or more cells. 2. Cells are the smallest and most basic functional units of life. 3. All cells arise from pre-existing cells.

What fundamental cellular and structural characteristics distinguish prokaryotic cells from eukaryotic cells?

Prokaryotes lack a membrane-bound nucleus and membrane-bound organelles, have a single circular DNA chromosome plus plasmids, replicate via binary fission, and are small ($0.1\text{ to }5\,\mu\text{m}$). Eukaryotes possess a membrane-bound nucleus, multiple linear chromosomes, membrane-bound organelles, replicate via mitosis and meiosis, and are larger ($10\text{ to }100\,\mu\text{m}$).

How are the six kingdoms of life classified under the three overarching domains?

Domain Archaea contains Kingdom Archaea; Domain Bacteria contains Kingdom Bacteria; and Domain Eukarya contains Kingdoms Animalia, Fungi, Plantae, and Protista.

What are the primary functions of the rough endoplasmic reticulum, smooth endoplasmic reticulum, Golgi apparatus, and lysosomes?

The rough endoplasmic reticulum synthesises and modifies proteins via surface ribosomes. The smooth endoplasmic reticulum synthesises lipids. The Golgi apparatus modifies, sorts, and packages proteins for intracellular delivery or export. Lysosomes contain digestive enzymes that degrade cellular waste, foreign materials, and toxins.

What structural and genetic evidence supports the endosymbiosis theory for the evolutionary origin of mitochondria and chloroplasts?

Mitochondria and chloroplasts contain double membranes consistent with ancient engulfment via endocytosis, possess their own circular DNA unenclosed by a nucleus, contain their own prokaryotic-like ribosomes, replicate independently via binary fission, and have porin transport proteins in their outer membranes identical to those in prokaryotes.

What are the balanced net chemical equations for aerobic cellular respiration and photosynthesis?

Aerobic cellular respiration: $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + 36\text{ ATP}$. Photosynthesis: $6\text{CO}_2 + 6\text{H}_2\text{O} \xrightarrow{\text{sunlight, chlorophyll}} \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$.

What three structural features distinguish plant cells from animal cells?

Plant cells have a cellulose-based cell wall (absent in animal cells), chloroplasts for photosynthesis (absent in animal cells), and a large central vacuole that provides turgor support (animal cells have small, temporary vacuoles, or none).

Why is a high surface area to volume ratio ($\text{SA:V}$) critical for cellular survival, and how do specialised cells maximise it?

A high $\text{SA:V}$ ensures efficient nutrient uptake and rapid waste removal across the plasma membrane while reducing intracellular diffusion distances. Cells maximise $\text{SA:V}$ by remaining small, adopting flattened or elongated forms, or folding their membranes into structures like villi and microvilli.

In this phospholipid molecule, what are the identity, chemical makeup, and polarity of regions X and Y?

Region X is the polar, hydrophilic phosphate head composed of a glycerol molecule and a negatively charged phosphate group. Region Y represents the two nonpolar, hydrophobic fatty acid tails composed of uncharged hydrocarbon chains.

Why is the plasma membrane represented by the 'fluid mosaic model'?

The membrane is described as 'fluid' because individual phospholipids and proteins move laterally and rotate dynamically within the bilayer; it is described as a 'mosaic' because diverse proteins, carbohydrates, and cholesterol molecules are embedded throughout the phospholipid bilayer.

How do cholesterol and the saturation level of fatty acids regulate membrane fluidity across hot and cold temperatures?

In high temperatures, cholesterol increases nonpolar interactions between fatty acid tails to prevent phospholipids from drifting apart. In low temperatures, cholesterol breaks up fatty acid packing; additionally, unsaturated fatty acids with kinks from double or triple carbon bonds prevent tight packing, maintaining fluidity.

What molecular characteristics determine whether a substance can cross the plasma membrane via simple diffusion?

Substances must be small and nonpolar/hydrophobic (e.g., $\text{O}_2$, $\text{CO}_2$, and small lipids) to dissolve through the nonpolar fatty acid core of the bilayer. Large or charged/polar hydrophilic molecules (e.g., glucose, amino acids, ions like $\text{Na}^+$ and $\text{Cl}^-$) are repelled by the hydrophobic core and cannot diffuse directly.

What are the structural mechanisms of protein channels and carrier proteins in facilitated diffusion?

Protein channels are fixed transmembrane pores that allow specific polar molecules or ions to diffuse down their concentration gradient. Carrier proteins bind a target molecule, undergo a conformational shape change to push it across the membrane down its concentration gradient, and return to their original shape without using $\text{ATP}$.

What happens to animal and plant cells when placed into hypertonic and hypotonic environments?

In a hypertonic solution (higher solute concentration outside), water leaves cells via osmosis, causing animal cells to shrivel and plant cells to become plasmolysed. In a hypotonic solution (lower solute concentration outside), water enters cells via osmosis, causing animal cells to swell and lyse, whereas plant cells become turgid as the rigid cell wall prevents bursting.

What are the three steps of protein-mediated active transport across a cell membrane?

1. Binding: The target molecule binds to a specific protein pump on one side of the membrane. 2. Conformational change: Hydrolysis of $\text{ATP} \rightarrow \text{ADP} + \text{P}_i$ releases energy, inducing a shape change in the pump. 3. Release: The target molecule is released on the opposite side of the membrane against its concentration gradient.

How do exocytosis and endocytosis operate, and what distinguishes phagocytosis from pinocytosis?

Exocytosis transports secretory products in vesicles from the Golgi apparatus to the membrane, fusing with the bilayer to release contents outside the cell. Endocytosis folds the membrane inward to trap extracellular substances, budding into a vesicle inside the cell. Phagocytosis is the endocytosis of solid material ('cell eating'), while pinocytosis is the endocytosis of dissolved liquids ('cell drinking').

What are the three primary purposes of cell replication in living organisms?

1. Growth and development (allowing single-celled zygotes to develop into multicellular organisms by increasing cell numbers). 2. Maintenance and repair (replacing aged, dead, or damaged tissues). 3. Reproduction (allowing prokaryotic and eukaryotic organisms to enlarge their population via asexual or sexual division).

What events occur at stages X, Y, and Z during bacterial binary fission?

Stage X: DNA replication, where the circular prokaryotic chromosome and plasmids uncoil and replicate. Stage Y: Elongation and septum formation, where the cell lengthens, chromosomes migrate to opposite poles, and the membrane pinches inward forming a septum. Stage Z: Cell division, where a new cell wall and membrane complete the separation of two genetically identical daughter cells.

What key cellular events occur in the $G_1$, $S$, and $G_2$ sub-phases of interphase, and what occurs in the $G_0$ phase?

$G_1$ involves cell growth, cytosol expansion, organelle replication, and protein synthesis. $S$ phase replicates nuclear DNA, producing sister chromatids joined at a centromere. $G_2$ involves continued cell growth and protein synthesis in preparation for mitosis. $G_0$ is a resting stage where cells are either quiescent (dormant, able to re-enter the cell cycle) or terminally differentiated (permanently non-dividing).

What are the definitive chromosomal and nuclear events of prophase, metaphase, anaphase, and telophase during mitosis?

Prophase: Chromatin condenses into distinct chromosomes around histones, centrioles migrate to poles, spindle fibres form, and the nuclear membrane breaks down. Metaphase: Spindle fibres attach to centromeres and align chromosomes along the cell equator. Anaphase: Spindle fibres contract, splitting centromeres and pulling sister chromatids to opposite poles. Telophase: Chromosomes decondense at poles, two genetically identical nuclear membranes reform, and spindle fibres disintegrate.

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

In animal cells, cytokinesis occurs when a cleavage furrow forms and pinches the plasma membrane inward, dividing the cell into two. In plant cells, the rigid cell wall prevents pinching; instead, Golgi-derived vesicles gather at the equator to assemble a cell plate, which develops into new cell walls and membranes separating the two daughter cells.

What cellular conditions are inspected at the $G_1$, $G_2$, and Metaphase checkpoints of the eukaryotic cell cycle?

The $G_1$ checkpoint verifies cell size, adequate nutrient/oxygen supply, sufficient protein synthesis for DNA replication, and absence of DNA damage. The $G_2$ checkpoint confirms that DNA replicated accurately in the $S$ phase without errors. The Metaphase checkpoint confirms that spindle fibres have correctly assembled and attached to chromosome centromeres along the equator.

How are the mitochondrial (intrinsic) and death receptor (extrinsic) pathways of apoptosis initiated, and how do they converge?

The mitochondrial pathway is initiated by internal cellular stress or DNA damage, prompting mitochondria to release cytochrome c into the cytosol to form an apoptosome. The death receptor pathway is initiated when extracellular death signalling molecules bind to death receptor proteins on the plasma membrane. Both pathways converge by activating intracellular caspase enzymes.

What four sequential morphological stages occur in a cell following caspase activation during apoptosis?

1. Caspase activation cleaves intracellular proteins. 2. Digestion of cell contents leads to organelle breakdown. 3. Cell shrinkage occurs as structural integrity collapses. 4. Membrane blebbing occurs as the cytoskeleton degrades, pinching the cell into membrane-bound apoptotic bodies that are cleared by phagocytes via phagocytosis.

What biological hallmarks distinguish benign tumours from malignant cancerous tumours?

Both benign and malignant tumours exhibit self-sufficiency in growth signals, antigrowth deactivation, and resistance to apoptosis. However, benign tumours remain localized within a capsule, whereas malignant tumours acquire the unique capacity for tissue invasion and metastasis, breaking into blood or lymph vessels to establish secondary tumours at distant sites.

What defines the differentiation capacities of totipotent, pluripotent, and multipotent stem cells?

Totipotent stem cells can differentiate into any cell type, including all embryonic and extraembryonic/placental tissues (e.g., the zygote). Pluripotent stem cells can differentiate into all cell types of the body across the three germ layers (ectoderm, mesoderm, endoderm) but cannot form placental tissue (e.g., embryonic stem cells). Multipotent stem cells can differentiate only into a limited number of specialised cell types within a specific organ or tissue (e.g., haematopoietic bone marrow stem cells).