Module 1: Introduction

●​ Why study Biology? Its importance, especially for engineers.

○​ Understanding natural systems: Biology provides insights into how living

organisms function, from the molecular to the ecosystem level. This knowledge is
crucial for engineers designing systems that interact with or are inspired by nature.

○​ Biomimicry: Nature has optimized solutions over billions of years of evolution.

Studying biology helps engineers find inspiration for novel designs, materials, and
processes.

○​ Bio-inspired engineering: Developing new technologies for healthcare (medical

devices, prosthetics), environmental solutions (bioremediation, sustainable energy),
and advanced materials (self-healing, lightweight structures).

○​ Addressing global challenges: Biology is central to solving issues like food

security, disease control, climate change, and sustainable resource management,
all of which require engineering solutions.

○​ Interdisciplinary collaboration: Engineers increasingly work with biologists,

necessitating a foundational understanding of biological principles.

●​ Differences between science and engineering (Eye/Camera, Bird/Aircraft

analogies).

○​ Science (e.g., Biology): Seeks to understand how the natural world works. It's
about discovery, observation, experimentation, and developing theories to explain
phenomena.

■​ Eye: A biologist studies the eye to understand its structure, function, and how
it evolved to perceive light and form images.
■​ Bird: A biologist studies how birds fly, the aerodynamics of their wings, their
muscle structure, and their migratory patterns.

○​ Engineering: Applies scientific principles to design and build solutions to problems.

It's about innovation, creating useful products, systems, and processes.

■​ Camera: An engineer designs a camera to capture images, using principles

of optics, electronics, and materials science, inspired by the eye's function but
optimized for different purposes.

■​ Aircraft: An engineer designs an aircraft for efficient flight, utilizing principles

of aerodynamics and materials science, inspired by bird flight but not directly
copying it, considering payload, speed, and safety.

●​ What is biomimicry?
 ○​ Biomimicry is an innovative approach that seeks sustainable solutions to human
challenges by emulating nature's time-tested patterns and strategies. It's about
learning from and mimicking the forms, processes, and ecosystems of nature to
create designs that are functional, sustainable, and beautiful. Examples include
Velcro (burrs), swimsuits (shark skin), and self-cleaning surfaces (lotus leaf).

Module 2: Biological Classification

●​ Difference between prokaryotic and eukaryotic cells.
Feature Prokaryotic Cells Eukaryotic Cells
Nucleus Absent (genetic material in Present (membrane-bound)
nucleoid region)
Organelles Absent (no membrane-bound Present (e.g., mitochondria,
organelles) ER, Golgi, chloroplasts)
Size Generally smaller (1-10 µm) Generally larger (10-100 µm)
DNA Circular, single chromosome; Linear, multiple chromosomes
plasmids often present in nucleus;
mitochondrial/chloroplast DNA
Ribosomes Smaller (70S) Larger (80S)
Cell Division Binary fission Mitosis and Meiosis
Examples Bacteria, Archaea Animals, Plants, Fungi, Protists

●​ Characteristics of the five kingdoms (Monera, Protista, Fungi, Plantae, Animalia) -

focus on key distinguishing features (cell type, number of cells, nutrition mode).

Kingdom Cell Type Number of Cells Nutrition Mode Key Distinguishing

Features
Monera Prokaryotic Unicellular Autotrophic No nucleus, no
(chemosynthesis, membrane-bound
photosynthesis) or organelles.
Heterotrophic Includes bacteria
and archaea.
Protista Eukaryotic Mostly Unicellular, Autotrophic Diverse group;
some multicellular (photosynthesis) "catch-all" for
or Heterotrophic eukaryotes not
(ingestion, fungi, plants, or
absorption) animals.
Fungi Eukaryotic Mostly Heterotrophic Cell walls made of
Multicellular, some (absorption) chitin; reproduce
unicellular (yeast) by spores; external
digestion.
Plantae Eukaryotic Multicellular Autotrophic Cell walls made of
(photosynthesis) cellulose; contain
chloroplasts;
typically
Kingdom Cell Type Number of Cells Nutrition Mode Key Distinguishing
Features
non-motile.
Animalia Eukaryotic Multicellular Heterotrophic No cell walls;
(ingestion) typically motile;
complex organ
systems.

●​ The three domains of life (Archaea, Bacteria, Eukarya) and why it's related to six
kingdoms.

○​ The three domains of life (Archaea, Bacteria, Eukarya) represent a higher level of
classification than kingdoms, based primarily on genetic and biochemical
differences, particularly in ribosomal RNA.

○​ Archaea and Bacteria are both prokaryotic and were previously grouped under the
single Kingdom Monera. However, genetic analysis revealed that Archaea are as
different from Bacteria as they are from Eukaryotes, leading to their separation into
distinct domains.

○​ The Eukarya domain encompasses all eukaryotic organisms, which are further
divided into the traditional eukaryotic kingdoms: Protista, Fungi, Plantae, and
Animalia.

○​ Relation to six kingdoms: While the initial five-kingdom system was widely used,
the recognition of the three domains led to a refinement. The Kingdom Monera was
split into two new kingdoms: Archaebacteria (now part of Archaea domain) and
Eubacteria (now part of Bacteria domain). This results in some modern
classification systems referring to six kingdoms: Archaebacteria, Eubacteria,
Protista, Fungi, Plantae, and Animalia. The three-domain system is a more
fundamental and evolutionarily accurate classification.

●​ Briefly know why E.coli, D. melanogaster, and C. elegans are used as model
organisms.

○​ Model organisms are non-human species that are extensively studied to

understand particular biological phenomena, with the expectation that the
discoveries made will be applicable to other organisms, especially humans. They
are chosen due to a combination of practical and scientific advantages.

○​ E. coli (bacteria):
■​ Rapid growth and short generation time.
■​ Simple genetic makeup (small, easily manipulated genome).
■​ Easy to culture in the lab.
■​ Used extensively in genetics, molecular biology (DNA replication, gene
expression), and biotechnology.
 ○​ Drosophila melanogaster (fruit fly):
■​ Short life cycle.
■​ Easy to breed in large numbers.
■​ Large chromosomes (polytene) for genetic analysis.
■​ Many identifiable mutations.
■​ Used extensively in genetics, developmental biology, neurobiology, and
studies of disease.

○​ C. elegans (nematode worm):

■​ Transparent body, allowing direct observation of cell division and
development.
■​ Fixed number of somatic cells (959 for hermaphrodites), allowing for precise
mapping of cell lineages.
■​ Simple nervous system.
■​ Short life cycle.
■​ Used extensively in developmental biology, neurobiology, programmed cell
death (apoptosis), and aging research.

Module 3: Genetics
●​ Difference between Mitosis and Meiosis.
Feature Mitosis Meiosis
Purpose Growth, repair, asexual Sexual reproduction (gamete
reproduction formation)
Cells Involved Somatic cells Germ cells (sperm/egg
precursors)
Number of Divisions One Two (Meiosis I and Meiosis II)
Daughter Cells Two Four
Chromosome Number Diploid (2n) - same as parent Haploid (n) - half of parent cell
cell
Genetic Variation No (daughter cells are Yes (crossing over,
genetically identical) independent assortment)

●​ Mendel's Laws of Segregation and Independent Assortment (basic principles).

○​ Law of Segregation: During the formation of gametes (sperm or egg cells), the two
alleles for a heritable character (e.g., flower color) segregate (separate) from each
other, so that each gamete carries only one allele for that character. When
fertilization occurs, the zygote receives one allele from each parent.

○​ Law of Independent Assortment: Alleles for different genes (e.g., seed color and
seed shape) assort independently of each other during gamete formation. This
means that the inheritance of one trait does not influence the inheritance of another,
as long as the genes are on different chromosomes or are far apart on the same
chromosome.

●​ Define Gene and Allele.

 ○​ Gene: A basic unit of heredity; a specific sequence of DNA (or RNA in some
viruses) that codes for a particular protein or functional RNA molecule, thereby
influencing a specific trait or characteristic.
○​ Allele: One of two or more alternative forms of a gene that arise by mutation and
are found at the same place (locus) on a chromosome. For example, for the gene
determining flower color, there might be an allele for purple flowers and an allele for
white flowers.

●​ What is Epistasis?

○​ Epistasis is a phenomenon where the expression of one gene is affected, modified,

or masked by one or more other genes. In other words, one gene's presence or
absence can prevent or alter the expression of another gene, even if the second
gene has its own distinct alleles. This often results in modified Mendelian ratios in
genetic crosses.

●​ What are the main phases of the Cell Cycle?

○​ The cell cycle is the series of events that take place in a cell leading to its division
and duplication of its DNA to produce two daughter cells.
○​ Interphase: The longest phase, during which the cell grows, copies its DNA, and
prepares for division. It consists of three sub-phases:
■​ G1 phase (First Gap): Cell growth, normal metabolic roles, synthesis of
proteins and organelles.
■​ S phase (Synthesis): DNA replication occurs; each chromosome is
duplicated, resulting in two sister chromatids.
■​ G2 phase (Second Gap): Cell continues to grow, synthesizes proteins and
organelles, and prepares for mitosis.
○​ M phase (Mitotic Phase): The actual cell division phase.
■​ Mitosis: Division of the nucleus (Prophase, Prometaphase, Metaphase,
Anaphase, Telophase).
■​ Cytokinesis: Division of the cytoplasm, forming two separate daughter cells.

Module 4: Biomolecules
●​ The four major classes of biomolecules (Carbohydrates, Lipids, Proteins, Nucleic
Acids).
●​ Know the basic monomer units for each class.

Class of Biomolecule Basic Monomer Unit

Carbohydrates Monosaccharides (e.g., glucose, fructose)
Lipids No true monomer; composed of fatty acids and
glycerol (or other backbone)
Proteins Amino acids
Nucleic Acids Nucleotides (composed of a sugar, phosphate,
and nitrogenous base)
●​ Functions of carbohydrates, lipids, proteins, and nucleic acids.

○​ Carbohydrates:
■​ Primary energy source: Glucose is the main fuel for cellular respiration.
■​ Energy storage: Starch in plants, glycogen in animals.
■​ Structural components: Cellulose in plant cell walls, chitin in fungal cell
walls and insect exoskeletons.
■​ Cell recognition: Components of cell surface markers.
○​ Lipids:
■​ Long-term energy storage: Fats and oils.
■​ Structural components of membranes: Phospholipids form the lipid bilayer
of cell membranes.
■​ Hormones: Steroids (e.g., testosterone, estrogen).
■​ Insulation and protection: Adipose tissue in animals.
■​ Waterproofing: Waxes.
○​ Proteins:
■​ Enzymes: Catalyze biochemical reactions (e.g., amylase).
■​ Structural support: Collagen (connective tissue), keratin (hair, nails).
■​ Transport: Hemoglobin (oxygen transport), membrane channels.
■​ Defense: Antibodies.
■​ Hormones: Insulin.
■​ Movement: Actin and myosin in muscle contraction.
■​ Regulation: Gene expression regulation.
○​ Nucleic Acids:
■​ Genetic information storage: DNA stores the hereditary information of an
organism.
■​ Genetic information transfer: RNA plays roles in transmitting genetic
information from DNA to proteins (mRNA, tRNA, rRNA).
■​ Energy currency: ATP (adenosine triphosphate) is a nucleotide derivative
that acts as the primary energy currency.
■​ Coenzymes: NAD+, FAD.

●​ Basic structure of DNA (double helix, nucleotides, bases).

○​ Double Helix: DNA exists as a double helix structure, resembling a twisted ladder.
This structure was elucidated by Watson and Crick.
○​ Nucleotides: The basic building block of DNA. Each nucleotide consists of three
components:
1.​ A 5-carbon sugar: Deoxyribose.
2.​ A phosphate group.
3.​ A nitrogenous base: There are four types:
■​ Adenine (A)
■​ Guanine (G)
■​ Cytosine (C)
■​ Thymine (T)
○​ Bases: The two strands of the double helix are held together by hydrogen bonds
between complementary nitrogenous bases:
■​ Adenine (A) always pairs with Thymine (T) via two hydrogen bonds.
 ■​ Guanine (G) always pairs with Cytosine (C) via three hydrogen bonds.
○​ The "backbone" of each DNA strand is formed by alternating sugar and phosphate
groups, with the nitrogenous bases extending inwards from this backbone. The two
strands run in opposite directions (antiparallel).

Module 5: Enzymes
●​ What are enzymes and why are they important (biological catalysts)?

○​ Enzymes: Biological catalysts, which are typically proteins (though some RNA
molecules called ribozymes also have catalytic activity). They are highly specific for
the reactions they catalyze.

○​ Importance (biological catalysts):

■​ Speed up reactions: Enzymes dramatically increase the rate of biochemical
reactions without being consumed in the process. Without enzymes, most
metabolic reactions would occur too slowly to sustain life.
■​ Lower activation energy: They do this by providing an alternative reaction
pathway with a lower activation energy.
■​ Specificity: Each enzyme typically catalyzes only one or a very small
number of specific reactions, ensuring precise control over metabolic
pathways.
■​ Regulation: Their activity can be regulated, allowing cells to control their
metabolism in response to changing conditions.

●​ Lock and Key and Induced Fit models of enzyme action.

○​ Lock and Key Model: This older model proposes that the enzyme's active site (the
region where the substrate binds) has a rigid, pre-formed shape that perfectly
complements the shape of the substrate, much like a key fits into a specific lock.
The substrate "fits" directly into the active site.
○​ Induced Fit Model: This more accurate and widely accepted model suggests that
the active site of the enzyme is not rigidly fixed. Instead, when the substrate binds
to the active site, it induces a conformational change in the enzyme, causing the
active site to subtly alter its shape to achieve a tighter fit around the substrate. This
"induced fit" optimizes the enzyme-substrate interaction, bringing catalytic groups
into optimal positions for reaction.

●​ Factors affecting enzyme activity (Temperature, pH, Inhibitors).

○​ Temperature:
■​ Low temperature: Decreases enzyme activity because molecules move
more slowly, leading to fewer collisions between enzyme and substrate.
■​ Optimal temperature: The temperature at which the enzyme exhibits
maximum activity. For most human enzymes, this is around 37°C.
■​ High temperature: Increases kinetic energy, but beyond the optimum, it
causes denaturation.
 ■​ Denaturation: Irreversible loss of the enzyme's three-dimensional structure
(and thus its function) due to disruption of bonds (e.g., hydrogen bonds,
hydrophobic interactions) that maintain the active site's shape.
○​ pH:
■​ Optimal pH: The pH at which the enzyme exhibits maximum activity. This
varies greatly depending on the enzyme's location (e.g., pepsin in the
stomach has an optimal pH around 2, while amylase in the mouth has an
optimal pH around 6.7).
■​ Extreme pH (acidic or basic): Can alter the ionization state of amino acid
residues in the active site, disrupting ionic bonds and hydrogen bonds,
leading to changes in enzyme structure and eventual denaturation, thereby
reducing or eliminating activity.
○​ Inhibitors: Substances that reduce an enzyme's activity.

●​ What is enzyme inhibition (competitive vs. non-competitive - basic idea)?

○​ Enzyme inhibition: The process by which the activity of an enzyme is decreased
or stopped.
○​ Competitive Inhibition:
■​ An inhibitor molecule (often structurally similar to the substrate) binds
reversibly to the enzyme's active site, competing with the substrate for
binding.
■​ It prevents the substrate from binding, thus reducing the rate of reaction.
■​ Can often be overcome by increasing substrate concentration.
○​ Non-competitive Inhibition:
■​ An inhibitor molecule binds to a site on the enzyme other than the active site
(an allosteric site).
■​ This binding causes a conformational change in the enzyme, which alters the
shape of the active site and reduces its ability to bind the substrate or
catalyze the reaction, even if the substrate is bound.
■​ Cannot be overcome by increasing substrate concentration.

●​ Define Activation Energy and how enzymes affect it.

○​ Activation Energy (\Delta G^\ddagger): The minimum amount of energy required
for a chemical reaction to proceed. It's the energy barrier that reactants must
overcome to transform into products.
○​ How enzymes affect it: Enzymes lower the activation energy of a reaction. They
do not change the overall free energy change (\Delta G) of the reaction, nor do they
change the equilibrium of the reaction. Instead, they provide an alternative reaction
pathway that requires less energy input, thereby increasing the rate at which
equilibrium is reached.

Module 6: Information Transfer

●​ DNA as the genetic material.
○​ DNA (deoxyribonucleic acid) is the molecule that carries the genetic instructions
used in the growth, development, functioning, and reproduction of all known living
 organisms and many viruses. Its stability, replication mechanism, and ability to be
transcribed into RNA and translated into proteins make it the ideal medium for
storing and transmitting hereditary information.

●​ The Central Dogma of Molecular Biology (DNA -> RNA -> Protein).
○​ The Central Dogma describes the fundamental flow of genetic information in
biological systems. It states that genetic information flows generally in one direction:
■​ DNA: Stores the genetic blueprint.
■​ Replication: DNA can be copied to make more DNA.
■​ Transcription (DNA -> RNA): The genetic information encoded in DNA is
transcribed into messenger RNA (mRNA) molecules.
■​ Translation (RNA -> Protein): The sequence of nucleotides in mRNA is
translated into the sequence of amino acids in a protein.

○​ While the primary flow is DNA to RNA to protein, there are exceptions (e.g., reverse
transcription in some viruses where RNA is used as a template to synthesize DNA).

●​ What is DNA replication, transcription, and translation (brief definition of each)?

○​ DNA Replication: The biological process of producing two identical replicas of

DNA from one original DNA molecule. It occurs before cell division, ensuring that
each daughter cell receives a complete and identical set of genetic instructions.

○​ Transcription: The process by which the genetic information from a strand of DNA
is copied into a new molecule of messenger RNA (mRNA). This happens in the
nucleus of eukaryotic cells and the cytoplasm of prokaryotic cells. The DNA
sequence serves as a template for synthesizing an RNA molecule.

○​ Translation: The process by which the genetic code carried by mRNA is decoded
to produce a specific sequence of amino acids (a polypeptide chain, which folds
into a protein). This occurs on ribosomes in the cytoplasm. Transfer RNA (tRNA)
molecules bring specific amino acids to the ribosome according to the codons on
the mRNA.

Module 7: Macromolecular Analysis

●​ The hierarchy of protein structure (Primary, Secondary, Tertiary, Quaternary) - know
what each level represents.

○​ Primary Structure: The linear sequence of amino acids in a polypeptide chain.

This sequence is determined by the genetic code in DNA and dictates all
subsequent levels of protein structure. (Example: Ala-Gly-Val-Ser...).

○​ Secondary Structure: Localized, regular folding patterns of the polypeptide chain,

stabilized by hydrogen bonds between the backbone atoms (not side chains). The
most common types are:
 ■​ Alpha-helix (\alpha-helix): A spiral staircase-like structure.
■​ Beta-pleated sheet (\beta-sheet): A folded, corrugated sheet-like structure.

○​ Tertiary Structure: The overall three-dimensional shape of a single polypeptide

chain, including the folding of secondary structures and the interactions between
amino acid side chains (R-groups). These interactions include hydrogen bonds,
ionic bonds, disulfide bridges, and hydrophobic interactions. This is the functional
3D shape of a single protein.

○​ Quaternary Structure: The arrangement of multiple polypeptide subunits (two or

more tertiary structures) to form a functional protein complex. Not all proteins have
quaternary structure. (Example: Hemoglobin, which has four subunits).

●​ Key functions of proteins (e.g., enzymes, transport, structure).

○​ Enzymes: Catalyze biochemical reactions (e.g., amylase, DNA polymerase).

○​ Structural Support: Provide shape and strength to cells and tissues (e.g., collagen
in connective tissue, keratin in hair and nails, actin/tubulin in cytoskeleton).
○​ Transport: Move substances across cell membranes (e.g., channel proteins,
carrier proteins) or through the body (e.g., hemoglobin for oxygen transport).
○​ Defense: Protect the body against foreign invaders (e.g., antibodies).
○​ Movement: Essential for muscle contraction (actin, myosin) and cell motility.
○​ Hormones: Act as chemical messengers (e.g., insulin regulates blood sugar).
○​ Receptors: Receive signals from the outside of the cell (e.g., hormone receptors).
○​ Storage: Store amino acids (e.g., ovalbumin in egg whites, casein in milk).

Module 8: Metabolism
●​ ATP as the energy currency of the cell (structure and importance).

○​ ATP (Adenosine Triphosphate): The primary energy currency of the cell, providing
the readily available energy for most cellular processes.

○​ Structure: Composed of:

1.​ Adenine: A nitrogenous base.
2.​ Ribose: A 5-carbon sugar.
3.​ Three phosphate groups: These are linked by two high-energy phosphate
bonds.

○​ Importance: The energy for cellular work is released when the terminal phosphate
group is hydrolyzed from ATP, forming ADP (adenosine diphosphate) and inorganic
phosphate (\text{P}_i). This reaction is highly exergonic. Cells constantly regenerate
ATP from ADP and \text{P}_i using energy from processes like cellular respiration
and photosynthesis.
 ●​ Basic idea of Glycolysis (glucose breakdown) and the Citric Acid Cycle (Krebs
Cycle).
○​ Glycolysis:
■​ Location: Cytoplasm.
■​ Process: The breakdown of one molecule of glucose (a 6-carbon sugar) into
two molecules of pyruvate (a 3-carbon compound).
■​ Net Output: Produces a small amount of ATP (2 net ATP) and NADH
(electron carrier).
■​ Key Idea: It's the initial stage of glucose catabolism, occurring with or without
oxygen, and it prepares the way for further energy extraction in aerobic
respiration.

○​ Citric Acid Cycle (Krebs Cycle/TCA Cycle):

■​ Location: Mitochondrial matrix (eukaryotes), cytoplasm (prokaryotes).
■​ Process: Pyruvate (from glycolysis) is converted to Acetyl-CoA, which then
enters the cycle. Acetyl-CoA is completely oxidized, releasing carbon dioxide
(\text{CO}_2).
■​ Net Output: Generates ATP (or GTP), NADH, and FADH2 (other electron
carriers).
■​ Key Idea: It's a central metabolic pathway that completes the oxidation of
glucose (and other fuel molecules), producing abundant electron carriers
(NADH and FADH2) that will fuel the electron transport chain for large-scale
ATP production.

●​ What is Photosynthesis (energy synthesis)?

○​ Photosynthesis: The process by which green plants, algae, and some bacteria
convert light energy into chemical energy, storing it in the form of glucose (sugar).
○​ Location: Chloroplasts in eukaryotic photosynthetic organisms.
○​ Overall Equation: 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
○​ Key Idea: It's the foundation of most food chains on Earth, converting inorganic
compounds (\text{CO}_2 and \text{H}_2\text{O}) into organic compounds
(\text{C}_6\text{H}_{12}\text{O}_6) using sunlight as the energy source, and
releasing oxygen as a byproduct. It consists of two main stages: light-dependent
reactions (capture light energy) and light-independent reactions (Calvin cycle,
synthesize sugars).

Module 9: Microbiology
●​ Difference between prokaryotic and eukaryotic microorganisms.
Feature Prokaryotic Microorganisms Eukaryotic Microorganisms
(e.g., Bacteria, Archaea) (e.g., Fungi, Protozoa, Algae)
Cell Structure No nucleus, no True nucleus,
membrane-bound organelles membrane-bound organelles
DNA Circular, in cytoplasm Linear, in nucleus
(nucleoid)
Feature Prokaryotic Microorganisms Eukaryotic Microorganisms
(e.g., Bacteria, Archaea) (e.g., Fungi, Protozoa, Algae)
Size Typically smaller (0.2-10 µm) Typically larger (10-100 µm)
Complexity Simpler, often unicellular More complex, can be
unicellular or multicellular
Reproduction Binary fission Mitosis, meiosis, budding,
spores, etc.

●​ Major groups of microorganisms (Bacteria, Fungi, Viruses, Protozoa, Algae) - know

a key characteristic for each.

Group Key Characteristic

Bacteria Prokaryotic, unicellular; reproduce by binary
fission; have peptidoglycan in cell walls; diverse
metabolisms (autotrophic/heterotrophic,
aerobic/anaerobic).
Fungi Eukaryotic; mostly multicellular (except yeast);
heterotrophic by absorption; cell walls made of
chitin; reproduce by spores; can be
decomposers, pathogens, or symbionts.
Viruses Acellular (not cells); obligate intracellular
parasites (require a host cell to replicate);
consist of genetic material (DNA or RNA)
enclosed in a protein coat (capsid); extremely
small.
Protozoa Eukaryotic, unicellular; heterotrophic (ingest
food particles); typically motile (using flagella,
cilia, or pseudopods); found in aquatic
environments.
Algae Eukaryotic; can be unicellular or multicellular;
autotrophic (photosynthetic) using chlorophyll;
generally aquatic; have cell walls but usually
lack true roots, stems, and leaves.
●​ Types of microscopy (Optical, Electron) and when they are used.

○​ Optical (Light) Microscopy:

■​ Principle: Uses visible light and a system of lenses to magnify specimens.
■​ Types: Brightfield, darkfield, phase contrast, fluorescence, confocal.
■​ When used: To observe living cells and their activities, general morphology
of cells and tissues, stained samples, and when relatively lower magnification
(up to ~1000-2000x) is sufficient. Good for observing bacteria, fungi,
protozoa, and larger cellular structures.

○​ Electron Microscopy:
■​ Principle: Uses a beam of electrons instead of light to create a magnified
image. Electrons have much shorter wavelengths than light, leading to
significantly higher resolution and magnification.
■​ Types:
■​ TEM (Transmission Electron Microscope): Electrons pass through a
very thin specimen, providing high-resolution internal structure details
(ultrastructure).
■​ SEM (Scanning Electron Microscope): Electrons scan the surface of
a specimen, creating a detailed 3D image of the surface topography.

■​ When used: To observe incredibly fine details of cellular organelles, viruses,

macromolecules, and surface features. Required for visualizing structures
smaller than what light microscopy can resolve (e.g., ribosomes, individual
protein complexes, viral particles). Specimens must be non-living and
typically prepared in a vacuum.