Biology Chapter 2: Cells and Molecules of Life

Flashcards covering chemical constituents of life, cell discovery, light and electron microscopy, eukaryotic and prokaryotic cell structures, and levels of biological organization based on Biology Chapter 2 notes.

How does water function as a chemical reactant in living organisms?

Water directly participates in biochemical reactions; for example, photosynthesis utilizes water and carbon dioxide to produce food and oxygen.

How does water act as a cooling agent in organisms?

Evaporation of water removes heat from the body, such as when the evaporation of sweat cools the skin.

How does water provide mechanical support in plants?

Water-filled plant cells become turgid and press against one another, which helps support the structure of the plant.

What is the primary biological role of nitrate ions in plants?

Nitrate provides a nitrogen source that plants require to synthesize proteins.

What are two key biological functions of magnesium ions?

Magnesium forms an essential part of chlorophyll in plants and acts as an activator for certain enzymes.

What is the biological function of iron in the human bloodstream?

Iron is a component of haemoglobin, the oxygen-carrying molecule in red blood cells, and also activates some enzymes.

What roles do calcium ions play in animals and plants?

In animals, calcium forms part of bones and teeth and is required for blood clotting, muscle contraction, and nervous-system signalling. In plants, it strengthens cell walls.

What important molecules and structures contain phosphate ions?

Phosphate is a component of bones and teeth, phospholipids, and nucleic acids such as $DNA$. In plants, it is also used to synthesize phospholipids and nucleic acids.

How do plants and animals differ in their primary carbohydrate energy storage molecules?

Plants store energy in the form of starch, whereas animals store energy as glycogen.

What is the main biological function of cellulose?

Cellulose serves as a major structural constituent of plant cell walls.

What are the primary functions of triglycerides and phospholipids?

Triglycerides serve as long-term energy reserves, reduce heat loss, and cushion internal organs; phospholipids form the primary structural lipid of cell membranes.

What are the respective primary functions of DNA and RNA?

$DNA$ carries genetic information, while $RNA$ is directly involved in protein synthesis.

What did Robert Hooke observe in 1665, and what term did he coin?

Hooke examined dead cork tissue under a microscope and named the small box-like spaces "cells," which were actually the cell walls of dead cells.

What notable discovery was made by Antoni van Leeuwenhoek in 1674?

Antoni van Leeuwenhoek observed living microorganisms in pond water using a microscope.

What did Robert Brown discover in 1831?

Robert Brown described nuclei inside orchid-leaf cells.

What are the three core tenets of the Cell Theory proposed by Schleiden and Schwann?

(1) All organisms are made of one or more cells; (2) the cell is the basic unit of life; and (3) all cells come from pre-existing cells.

What are the imaging characteristics and maximum magnification of a light microscope?

A light microscope produces coloured images of living or dead specimens, requires relatively easy preparation, and reaches a maximum magnification of about $1{,}600\times$.

How do transmission electron microscopes (TEM) and scanning electron microscopes (SEM) differ in their images and maximum magnifications?

A TEM transmits electrons through a very thin section to produce a black-and-white, two-dimensional view of internal structures (up to $1{,}500{,}000\times$). An SEM scans the specimen surface to produce a black-and-white, three-dimensional view of external structures (up to $200{,}000\times$).

What does resolution mean in the context of microscopy?

Resolution is the ability to distinguish two close points or details as separate structures, which determines image clarity.

What formula relates magnification, image size, and actual object size?

$\text{Magnification} = \frac{\text{image size}}{\text{actual object size}}$, or $\text{actual object size} = \frac{\text{image size}}{\text{magnification}}$.

If a specimen image measures $0.6\,\text{cm}$ under a magnification of $400\times$, what is its actual size in micrometers ($\mu\text{m}$)?

$\text{Actual size} = 0.6\,\text{cm} \div 400 = 0.0015\,\text{cm} = 15\,\mu\text{m}$.

How do low-power and high-power microscope views compare regarding field of view, cell count, detail, and brightness?

Low power provides a larger field of view, more cells, fewer details, and a brighter image; high power provides a smaller field of view, fewer cells, more details, and a dimmer image.

Why must the coarse adjustment knob never be used while viewing under high power?

Using the coarse adjustment knob under high power can drive the objective lens into the slide, risking damage to both the objective and the glass slide.

What is the structure and permeability of the cell membrane?

The cell membrane is a thin, flexible barrier composed primarily of phospholipids and proteins that is differentially permeable, controlling the movement of substances into and out of the cell.

How does the plant cell wall differ from the cell membrane in composition and permeability?

The cell wall is a thick, rigid outer layer made mainly of cellulose and is fully permeable, whereas the cell membrane is thin, flexible, lipid-and-protein-based, and differentially permeable.

How do rough endoplasmic reticulum and smooth endoplasmic reticulum differ in structure and function?

Rough ER has ribosomes bound to its surface and synthesizes proteins; smooth ER lacks ribosomes and is the site of lipid synthesis.

What is the structural organization and primary function of a mitochondrion?

A mitochondrion has a double membrane with a folded inner membrane; it serves as the main site of aerobic respiration, releasing usable cellular energy from food molecules.

Why is the statement "all plant cells have chloroplasts" scientifically inaccurate?

Chloroplasts occur only in green photosynthetic cells (such as palisade mesophyll); non-green plant tissues, such as onion epidermal cells and root-hair cells, lack chloroplasts.

What are the contents and functions of the plant cell central vacuole?

The central vacuole contains cell sap (water, dissolved sugars, pigments, and wastes); when full of water, it exerts turgor pressure that keeps plant cells firm and supports the plant.

How do prokaryotic cells differ from eukaryotic cells with respect to the nucleus and membrane-bound organelles?

Prokaryotes lack a true nucleus (their $DNA$ lies free in the cytoplasm) and lack membrane-bound organelles; eukaryotes possess a membrane-enclosed nucleus and membrane-bound organelles like ER and mitochondria.

What are the key rules for drawing biological specimens under high power?

Use a sharp HB pencil; draw large, clear, smooth outlines in correct proportion; do not shade; use straight, uncrossed label lines without arrowheads; and include a descriptive title and magnification.

What are the five levels of body organization from simplest to most complex, illustrated with the digestive system?

Cell (smooth-muscle cell or epithelial cell) $\rightarrow$ Tissue (smooth-muscle tissue or epithelial tissue) $\rightarrow$ Organ (stomach) $\rightarrow$ Organ system (digestive system) $\rightarrow$ Organism (human).