Grade 10 Biology: Cell System, Membranes, and Cell Division

Comprehensive practice flashcards covering characteristics of life, cell theory, prokaryotic vs. eukaryotic cell structure, organelle functions, membrane dynamics and transport, and the stages of the cell cycle and mitosis.

What defines a living organism according to the characteristics of life?

A living organism is something made of one or more cells that carries out all necessary life processes. If something lacks cells, it is not considered alive, even if it appears active.

What seven biological processes are represented by the mnemonic MRS GREN?

Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, and Nutrition.

How is growth scientifically defined in living organisms?

A permanent increase in size and dry mass caused by an increase in cell number, cell size, or both. Temporary changes, such as a turgid plant leaf swelling with water, do not count as growth.

What is the biological difference between excretion and egestion?

Excretion is the removal from the body of metabolic waste products (such as $CO_2$ from respiration and urea from amino acid breakdown) and substances in excess of requirements. Egestion is the removal of undigested, unabsorbed food waste as feces.

What are the three core principles of the Cell Theory?

1. Cells are the basic unit of structure and function of all living things. 2. All organisms are composed of one or more cells. 3. All cells come from other cells by reproduction (division of one cell into two).

Based on the provided diagram of a bacterial cell, what are plasmids and what is their function?

Plasmids are small circular strands of DNA in prokaryotes that carry extra genes, such as those providing antibiotic resistance.

How do prokaryotic and eukaryotic cells compare in size, nuclear structure, and DNA organization?

Prokaryotes are smaller ($0.1$ to $5.0\,\mu m$), lack a membrane-bound nucleus, have circular DNA (a single haploid chromosome $n$), and lack membrane-bound organelles. Eukaryotes are larger ($10$ to $100\,\mu m$), possess a distinct membrane-bound nucleus, have linear DNA in paired diploid chromosomes ($2n$), and contain specialized organelles.

According to the comparison chart, which structural features distinguish a plant cell from an animal cell?

Plant cells have a cellulose cell wall, large central vacuole, and chloroplasts, and they lack centrosomes and lysosomes. Animal cells lack a cell wall and chloroplasts, contain small vacuoles, and have centrioles/centrosomes and lysosomes.

In this electron micrograph of an animal cell, which labeled structures help organize cell division by pulling chromosomes apart?

The centrioles.

What is cellular compartmentalization and why is it beneficial to eukaryotic cells?

Compartmentalization is the division of the cell into separate, membrane-bound spaces. It speeds up chemical reactions by concentrating enzymes and substrates, provides protection by containing destructive enzymes (e.g., inside lysosomes) or shielding DNA in the nucleus, and makes homeostasis easier to maintain.

What pathway do organelles follow to synthesize, package, and secrete a protein?

1. DNA in the nucleus is transcribed into mRNA. 2. mRNA is translated by ribosomes on the rough endoplasmic reticulum to form a protein. 3. The rough ER folds the protein and packages it into a transport vesicle. 4. The vesicle delivers the protein to the Golgi apparatus for sorting and modification. 5. A secretory vesicle carries the protein to the cell membrane to be released via exocytosis.

How do the cell membrane and cell wall differ in composition and occurrence?

The cell membrane is thin, flexible, made mainly of phospholipids and proteins, and found in all living cells. The cell wall is strong, rigid, made of materials like cellulose in plants, and found in plants, fungi, and bacteria, but not animal cells.

How does the amphipathic nature of phospholipids dictate the structure of the phospholipid bilayer?

Because water is present inside and outside the cell, polar hydrophilic phosphate heads naturally face outward toward the water, while nonpolar hydrophobic fatty acid tails face inward toward each other away from water.

Why is the cell membrane described by the 'fluid mosaic model'?

It is described as 'fluid' because phospholipids and many membrane proteins can move laterally within the membrane, and 'mosaic' because diverse proteins are embedded throughout the phospholipid bilayer like the tiles of a mosaic.

Based on the provided membrane transport diagram, how does a carrier protein differ mechanically from a channel protein?

A channel protein provides an open hydrophilic pore for specific ions or polar molecules to pass through, whereas a carrier protein binds the specific solute and physically changes its conformation (shape) to release it on the opposite side.

What is the biological function of the membrane component indicated by the arrow in the diagram?

Cholesterol regulates membrane fluidity and stability by preventing the membrane from becoming too fluid at high temperatures and preventing phospholipids from packing too closely together at low temperatures.

What are the fundamental differences between passive transport and active transport?

Passive transport moves substances down their concentration gradient (high to low) without requiring cellular energy ($\text{ATP}$). Active transport moves substances against their concentration gradient (low to high) using energy from respiration in the form of $\text{ATP}$ and specific carrier proteins.

What is simple diffusion and why does it not require ATP?

Simple diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration down a concentration gradient. It requires no $\text{ATP}$ because particles move continuously and randomly due to their own kinetic energy.

How is osmosis defined, and what role do aquaporins play?

Osmosis is the net movement of water molecules across a selectively permeable membrane from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration). Aquaporins are specialized channel proteins that facilitate rapid osmosis.

What happens to an animal cell when placed into a hypotonic solution versus a hypertonic solution?

In a hypotonic solution (lower solute outside), water enters by osmosis, causing the animal cell to swell and burst (cytolysis). In a hypertonic solution (higher solute outside), water exits the cell, causing it to shrink and shrivel (crenation).

What is plasmolysis in plant cells?

Plasmolysis is the shrinking of the plant cell cytoplasm and pulling away of the cell membrane from the rigid cell wall when placed in a hypertonic solution due to the loss of water by osmosis.

What is bulk transport, and how do endocytosis and exocytosis function?

Bulk transport is the active transport of large particles or quantities of substances using vesicles. In endocytosis, the membrane folds inward and pinches off to bring materials inside. In exocytosis, internal vesicles fuse with the cell membrane to release contents outside the cell.

What main events occur during the G1, S, and G2 phases of interphase?

In $G_1$ (Growth 1), the cell grows, carries out normal activities, and prepares cellular materials. In $S$ (Synthesis), DNA is replicated so each chromosome consists of two identical sister chromatids. In $G_2$ (Growth 2), the cell continues to grow and produces organelles and proteins needed for mitosis.

What are the structural differences between chromatin, chromosomes, and sister chromatids?

Chromatin is DNA associated with proteins in an uncondensed, loose form for accessibility during normal cellular activity. Chromosomes are highly condensed, coiled packages of DNA and proteins visible during division. Sister chromatids are two identical copies of a replicated chromosome joined at a centromere.

Why does the surface area-to-volume ratio (SA:V) force large cells to divide?

As a cell grows, its volume increases faster than its surface area. A smaller $\text{SA:V}$ ratio makes exchange of nutrients and metabolic wastes across the membrane too inefficient, necessitating cell division.

What occurs during metaphase and anaphase of mitosis?

In metaphase, duplicated chromosomes line up along the equator (metaphase plate) and spindle fibers attach to their centromeres. In anaphase, sister chromatids separate at the centromere and are pulled to opposite poles by the spindle fibers.

How does cytokinesis differ between animal cells and plant cells?

In animal cells, the cell membrane constricts inward (cleavage furrow) to pinch the cell into two. In plant cells, the rigid cell wall prevents pinching; instead, membrane-bound vesicles fuse along the middle to form a cell plate that develops into the new cell wall.

What are the three essential biological roles of mitosis, and what consequence arises if it becomes uncontrolled?

The three key roles of mitosis are organismal growth, tissue repair, and ongoing maintenance (replacing old/damaged cells). Uncontrolled mitosis leads to tumor development and cancer.