General Biology

Cytology – studies biology

Biology – Study of Life Robert Brown

Cell – Study of Life Discovered nucleus in 1831

Postulates of Cell Theory

- All living things are made up of cells Modern cell theory

- The basic unit of life - Energy flow occurs within cells

- Cells carry DNA which is passed from
- Every cell came from a pre-existing cell by
cell to cell during cell division
division
- All cells have the same basic
Robert Hooke - Micrographia chemical composition

He is the one who examined cork and called

the cell cell
CELL STRUCTURES AND FUNCTIONS
Matthias Schleiden

A botanist who claimed that all plants came

Organelle: “little organs”
from cells
Cell membrane: controls the in and out of
Theodor Schwann
the cell
a zoologist who claimed that all animals
Cell Wall: rigid membrane surrounding the
came from cells
plant cells
Rudolf Virchow
Nucleus: controls and regulates cell
“Omnis cellula e cellula” meaning All cells activities; Robert Brown 1831; also known
came from pre-existing cell by division as the Brain of the Cell

Zacharrias Jannsen Ribosomes: Protein factory of the cell,

doesn't have a membrane
Invented microscope
Mitochondria: The power house of the cell;
Anton Van Leeuwenhoek
produces chemical energy needed to power
Invented his own microscope and used it to the cell in the form of ATP (Adenosine
view pond water and scrapings from his Triphosphate)
teeth
Endoplasmic Reticulum: interconnected
membrane sacs and tubules
2 types of ER (DNA and
RNA)

Rough ER: has ribosomes attached Circular DNA Both types of Linear DNA
cells have a
Smooth ER: lacks ribosomes, lipid, steroid liquid
environment
synthesis known as the
cytoplasm
Golgi Apparatus: Sac-like membranes; packs
Unicellular May be
and distribute/transports lipids and proteins multicellular or
unicellular
Lysosome: Spherical shape inside the cell,
larger than transport vesicles but smaller Cells are Cells are larger
smaller in size in size
than nucleus
Has larger Has smaller
Chloroplast: site of photosynthesis; round, number of number of
organisms organisms
oval or disk-shaped body
Appeared 4 Appeared 1
Vacuoles: looks a lot like a water balloon; billion years billion years
maintains water balance ago ago

Cytoskeleton: long fibers that are arranged

in a network inside the cell
PLANT AND ANIMAL TISSUE CELL
Vesicle: self-contained structure consisting
of fluid or gas
TISSUE – formed with a group of cells
Peroxisome: involve in metabolic processes,
particularly lipid breakdown and
detoxification
Plant Tissues – comes in several forms;
vascular, epidermal, ground and
meristematic.
PROKARYOTIC AND EUKARYOTIC
TISSUE CELL TYPES FUNCTION
Prokaryotic Similarities Eukaryotic
S
Organelles Both types of Organelles
lack a cells have cell covered by a
membrane membranes membrane
(outer covering
of the cell)
Ribosomes are Both types of Multiple
the only cells have organelles
Epidermal Parenchyma Protect
organelles ribosomes including Tissue plant
ribosomes tissues and
Genetic Both types of Membrane
material floats cells have covered prevent
in the DNA Genetic water lose
cytoplasm material
 Ground Parenchyma, Makes up Zygote – embryo – ectoderm – mesoderm –
Tissue Collenchyma, bulk of endoderm
Schlerenchym plant mass
a
2. Connective Tissues – develop from
Meristemati Parenchyma Divide to the mesodermal cells of the embryo,
c Tissue produce they support and bind other tissues
new in the body
growth
Classification Function

Vascular Xylem is Xylem Connective Tissue Provides support &

Tissue made up of transports Proper protection to the
vessels & water, body
tracheid Phloem Vascular Tissue Transport of
Phloem is transports materials in the
made up of sugars body
sieve cells & Skeletal Tissue It supports the
companion body and gives it
cell proper shape and
form

Animal Tissue – a group of connected cells

that have a similar function within an 3. Muscular Tissue – develops from the
organism. mesoderm of the embryo. It is
classified into 3 types; cardiac,
smooth, and skeletal. Performs the
1. The Epithelial Tissue following functions;
Forms the protective covering and • It helps in movements &
inner lining of the bode & organs. locomotions
• Supports the bones and
other structures
Classification Function
• Responsible for peristalsis
Sensory Epithelium To perceive stimuli
Glandular Secretes chemicals and parturition
Epithelium Classification Function
Pigmented Imparts color in Cardiac It helps in blood
Epithelium retina circulation & keeps
Absorptive For absorption the heart pumping
Epithelium Smooth These helps in
peristalsis and
 other involuntary Flagella – long whip like structures
functions of the
body Formed from microtubules
Skeletal Provide, support,
help in movement,
& maintain Villi & Microvilli
homeostasis
Villi – smaller projection

4. The Nervous Tissue – makes up the Microvilli – finger-like projections

peripheral and the central nervous
system. Found in the brain, spinal
cord, & nerves. Pseudopods – temporary, irregular lobes
formed by amoebas
Classification Function
Neuron/Nerve Cell These are the
structural and
Extra Cellular Matrix (ECM)
functional unit of
nervous system - Compound secreted by the cell on
Neuroglia Theses are special its apical surface
cells found in the
brain & spinal cord.
They provide
support to the 2. Basal Modification – cell
neurons and fibers. modification found on the basal
Neurosecretory Theses function as surface of the cell
Cells endocrine organs. Desmosomes/Hemidesmosomes –
They release primarily composed of keratin,
chemical from the
integrins & cadherins
axons directly into
blood.
3. Lateral Modification – found on the
basal surface of the cell
CELL MODIFICATION – re-acquired by the
cell after cell division Tight Junction – act as barriers that regulate
the movement of water

Adhering Junction – anchoring junction on

1. Apical Modification – found on the the lateral surface of the cell
apical surface
Gap Junction – also known as
Cilia & Flagella communicating junctions
Cilia – usually short, hair like structure that
move in waves
CELL CYCLE AND THEIR CONTROL POINTS The duration of cell cycle varies from hours
to years; a typical human cell duration is
90hrs
Cell Cycle – a series of events that a cell
INTERPHASE – the longest phase; in typical
passes through from the time until it
human cell, the 90 hrs, interphase lasts for
reproduces its replica. Growth and division
89 hrs
of single cell into a daughter cell and
duplication (replication). CHARACTERISTIC – the resting phase of the
cell; resting refers to the the rest from
division; metabolically active; metabolic
PROKARYOTIC – cell cycle occurs via a activities are high in this phase; the cell
process termed binary fission grows during this phase; during this phase
mRNA and rRNA are synthesized;
EUKARYOTIC – cell cycle can be divided into
chromosomes divides into two chromatids;
two period which are;
centrioles duplicate into two; two centrioles
a.) interphase are formed; centrospheres of centrioles,
microtubules arise.
b.) mitosis
STAGES OF INTERPHASE: consists 3 sub-
stages. They are;
PHASES OF CELL CYCLE
• G1 PHASE – the cell grows in size,
2 major activities: synthesizes mRNA and proteins
INTERPHASE necessary for DNA replication, and
replicates organelles
G1 (pre-synthetic phase) • S PHASE – DNA replication
S (DNA synthesis) • G2 PHASE – the cell replenishes its
energy stores, synthesizes proteins
G2 (pre-mitotic phase)
necessary for chromosome
CELL DIVISION (MITOTIC PHASE) manipulation, duplicates some
organelles, and recognizes
a) INTERPHASE – during this phase the
cytoskeleton.
cell grows, accumulating nutrients
needed for mitosis and duplicating
its DNA
M PHASE (MITOSIS)
b) MITOSIS (M)-phase – during which
cell splits itself into two different cell The M phase, or mitosis, is when a

eukaryotic cell separates its duplicated

chromosomes and divides into two

identical daughter cells. It consists of two Chromosomes align along the metaphase

tightly coupled processes: mitosis and plate (the equator of the cell).

cytokinesis. Each chromosome is attached to spindle

fibers from opposite poles.

Mitosis: The process of nuclear division, Anaphase:

divided into distinct stages: prophase, Sister chromatids separate and move to

prometaphase, metaphase, anaphase, and opposite poles of the cell.

telophase. The cell elongates as microtubules

Cytokinesis: The division of the lengthen.

cytoplasm, resulting in two separate Telophase:

daughter cells. Chromosomes arrive at the poles and

begin to decondense.

Stages of Mitosis The nuclear envelope reforms around

each set of chromosomes.

Prophase: The mitotic spindle disappears.

Chromatin condenses into visible

chromosomes. Cytokinesis

The nuclear envelope starts to break

down. Usually starts during late anaphase or

The mitotic spindle begins to form. early telophase.

Prometaphase: In animal cells, a cleavage furrow forms,

The nuclear envelope completely breaks pinching the cell in two.

down. In plant cells, a cell plate forms, eventually

Chromosomes attach to the mitotic becoming the new cell wall.

spindle via kinetochores.

Metaphase:
M phase ensures accurate chromosome Key Checkpoints

segregation and is crucial for growth,

repair, and asexual reproduction in G1/S Checkpoint:

eukaryotes. Errors in M phase can lead to Function: Assesses DNA damage before

aneuploidy (abnormal chromosome the cell enters S phase (DNA replication).

number) and potentially cancer. Mechanism: Involves the tumor

suppressor protein p53, which activates

CELL CYCLE CHECKPOINT DNA repair mechanisms or apoptosis if

Cell cycle checkpoints are crucial control DNA damage is detected . 35

mechanisms that ensure the fidelity of cell Proteins Involved: ATM, CHK2, p53, p21,

division in eukaryotic cells. These Cyclin/CDK complexes.

checkpoints monitor the integrity of DNA Intra-S Checkpoint:

and the proper execution of cell cycle Function: Monitors DNA replication

events, preventing the propagation of during S phase, responding to stalled

cells with damaged DNA or chromosomal replication forks or DNA damage.

abnormalities .
1 Mechanism: Involves ATR kinase, which

activates CHK1 to prevent further S-phase

Purpose: Cell cycle checkpoints halt cell progression.

cycle progression to allow time for DNA Proteins Involved: ATR, CHK1, CDC25A.

repair or, if the damage is irreparable, to G2/M Checkpoint:

trigger cell death or senescence .

24 Function: Ensures that DNA replication is

Checkpoints: The cell cycle has multiple complete and DNA damage is repaired

checkpoints, including G1/S, intra-S, before the cell enters mitosis.

G2/M, and the spindle assembly Mechanism: Regulated by the activity of

checkpoint (SAC) .35 Cyclin B/CDK1 complex, which is

inhibited by WEE1 and MYT1 kinases and Telophase), but meiosis involves two

activated by CDC25C phosphatase . 3 rounds of division (Meiosis I and Meiosis

Proteins Involved: ATM, ATR, CHK1, II), each with its own PMAT phases . 1

CHK2, WEE1, MYT1, CDC25C, Cyclin

B/CDK1. Mitosis
Spindle Assembly Checkpoint (SAC):
Mitosis occurs in somatic cells and is
Function: Ensures proper chromosome
essential for growth, repair, and asexual
segregation during mitosis by monitoring
reproduction. It consists of one round of
the attachment of spindle fibers to
cell division, resulting in two diploid
kinetochores.
daughter cells that are genetically
Mechanism: Lack of tension at
identical to the parent cell .
1

kinetochores triggers a signal that

prevents anaphase initiation.

Prophase: Chromatin condenses into
Proteins Involved: APC/C, MAD2,
visible chromosomes, and the nuclear
BUBR1, Aurora B kinase.
envelope breaks down. The mitotic

spindle begins to form .1

MITOSIS AND MEIOSIS

Metaphase: Chromosomes align at the
Mitosis and meiosis are essential
metaphase plate (the equator of the cell),
processes of cell division in eukaryotic
with spindle fibers attached to the
cells. Mitosis results in two identical
centromere of each chromosome . 1

daughter cells, while meiosis produces

Anaphase: Sister chromatids separate
four genetically diverse daughter cells
and move to opposite poles of the cell . 1

with half the number of chromosomes as

Telophase: The nuclear envelope reforms
the parent cell. Both processes involve
around each set of chromosomes, and
distinct phases known as PMAT
chromosomes decondense. Cytokinesis
(Prophase, Metaphase, Anaphase,
occurs, dividing the cytoplasm and Telophase I: Chromosomes arrive at

forming two daughter cells . 1 opposite poles, and the cell divides into

two haploid daughter cells .5

Meiosis I
Meiosis II
Meiosis I is the first round of cell division

in meiosis, resulting in two haploid cells. Meiosis II is the second round of cell

It is a reductional division, reducing the division in meiosis, similar to mitosis. It

chromosome number from diploid to separates sister chromatids, resulting in

haploid .
4 four haploid daughter cells .1

Prophase I: This is the longest phase of Prophase II: Chromosomes condense,

meiosis, during which chromatin and the nuclear envelope breaks down . 5

condenses, and homologous Metaphase II: Chromosomes align at the

chromosomes pair up to form tetrads metaphase plate .2

(bivalents). Crossing over occurs, Anaphase II: Sister chromatids separate

exchanging genetic material between non- and move to opposite poles . 2

sister chromatids, increasing genetic Telophase II: Chromosomes arrive at

diversity. The nuclear envelope breaks opposite poles, the nuclear envelope

down, and the spindle apparatus forms . 124 reforms, and cytokinesis occurs, resulting

Metaphase I: Homologous chromosome in four haploid daughter cells

pairs align at the metaphase plate . 2 ** Recombination is the process where

Anaphase I: Homologous chromosomes genetic material is exchanged between

separate and move to opposite poles, two DNA molecules or different segments

while sister chromatids remain attached . 5 of the same DNA molecule, resulting in

new combinations of genes.

SIGNIFICANCE FOR APPLICATION OF egg) that fuse during fertilization to form

MITOSIS AND MEIOSIS a diploid zygote.

Genetic Diversity: Meiosis generates

Mitosis genetic diversity through crossing over

and independent assortment. This

Growth and Development: Mitosis is
diversity is crucial for adaptation and
essential for the growth of multicellular
evolution.
organisms. It increases cell number,
Maintaining Chromosome Number:
allowing tissues and organs to develop
Meiosis ensures that each generation has
from a single fertilized egg.
the correct chromosome number by
Tissue Repair and Regeneration:
halving the chromosome number in
Mitosis replaces damaged or dead cells,
gametes.
enabling tissue repair and regeneration.
Evolutionary Adaptation: The genetic
Asexual Reproduction: In some
variation introduced by meiosis allows
organisms, mitosis is the basis for asexual
populations to adapt to changing
reproduction, producing genetically
environments.
identical offspring.

Cell Replacement: Mitosis continuously

DISEASES AND DISORDERS
replaces cells in tissues like skin and the

lining of the digestive tract.

Malfunctions in the cell cycle can lead to

various disorders and diseases, most

Meiosis
notably cancer. The cell cycle is a tightly
Sexual Reproduction: Meiosis is regulated process, and disruptions can
essential for sexual reproduction, result in uncontrolled cell growth, DNA
producing haploid gametes (sperm and damage, and genomic instability . 1
Cancer
Nondisjunction: Failure of chromosomes
Cancer arises from the uncontrolled
or chromatids to separate properly can
proliferation of cells due to the failure of
result in an abnormal number of
normal control mechanisms. This can
chromosomes in daughter cells. This can
occur when cell cycle checkpoints fail to
lead to conditions like Turner syndrome,
detect and repair DNA damage or when
Down syndrome (trisomy 21), and Patau
cells ignore signals to stop dividing .
12

syndrome (trisomy 13).

Neurodegenerative Diseases:
Common Cancers: Breast, lung, liver, and
Huntington's disease is an inherited
colon cancers, as well as leukemia, are
disorder that causes progressive nerve
frequently associated with cell cycle
cell death in the brain. Tay-Sachs disease
disorders . 3

is a rare inherited disorder that destroys

Tumor Formation: Rapid cell
nerve cells in the brain and spinal cord.
reproduction can lead to the formation of
Down Syndrome (Trisomy 21):
tumors, which may invade normal tissues
Cause: An extra copy of chromosome 21,
and organs . 3

usually due to nondisjunction during

Metastasis: Cancer cells can spread to
meiosis I in the egg cell .
24

other parts of the body, causing secondary

Characteristics: Intellectual disability,
tumors .3

characteristic facial features, and other

health problems.
Genetic Disorders
Turner Syndrome (X0):
Cell cycle malfunctions can also result in Cause: Females have only one X
genetic disorders, often due to errors in chromosome instead of two, often due to
chromosome segregation during cell nondisjunction in sperm or egg cells . 24

division . 1
Characteristics: Short stature, infertility, Monosomy: The absence of one

and other physical abnormalities. chromosome from a pair (2n - 1). For

Klinefelter Syndrome (XXY): example, Turner syndrome in females,

Cause: Males have an extra X where there is only one X chromosome

chromosome, typically due to (XO).

nondisjunction during meiosis I or II .24 Trisomy: The presence of an extra copy of

Characteristics: Reduced fertility, small one chromosome (2n + 1). Examples

testes, and development of some female include Down syndrome (trisomy 21),

characteristics. Edwards syndrome (trisomy 18), and

Patau Syndrome (Trisomy 13): Patau syndrome (trisomy 13).

Cause: An extra copy of chromosome 13.

Characteristics: Severe intellectual Polyploidy

disability and physical abnormalities.
Polyploidy is a condition in which a cell or
Edwards Syndrome (Trisomy 18):
organism has more than two complete
Cause: An extra copy of chromosome 18.
sets of chromosomes. This is common in
Characteristics: Severe intellectual
plants but rare in animals.
disability and physical abnormalities.

Aneuploidy
Triploidy (3n): Three sets of

Aneuploidy refers to a condition in which chromosomes. In humans, triploidy is

a cell has an abnormal number of usually lethal.

chromosomes, differing from the normal Tetraploidy (4n): Four sets of

diploid number. This typically results chromosomes. Can occur in some human

from nondisjunction during meiosis or cells but is not viable in a complete

mitosis. organism.

CELL MEMBRANE
The cell membrane, also known as the Fluid Mosaic Model: The cell membrane

plasma membrane, is a biological is described by the fluid mosaic model,

membrane that separates the interior of a which suggests that the membrane is a

cell from its external environment. It is a dynamic structure with lipids and

selectively permeable barrier that proteins that can move laterally.

regulates the movement of substances in

and out of the cell. Functions

Selective Permeability: The cell

Structure
membrane controls the movement of

Phospholipid Bilayer: The basic substances in and out of the cell. Small,

framework of the cell membrane is a nonpolar molecules can pass through

double layer of phospholipid molecules. easily, while larger, polar molecules and

Each phospholipid has a hydrophilic ions require transport proteins.

(water-attracting) head and two Cell Signaling: Receptors on the cell

hydrophobic (water-repelling) tails. membrane bind to signaling molecules,

Proteins: Proteins are embedded within transmitting signals into the cell.

the lipid bilayer and perform various Cell Adhesion: Membrane proteins help

functions. cells adhere to each other and to the

Integral Proteins: Span the entire extracellular matrix.

membrane. Protection: The cell membrane provides

Peripheral Proteins: Attach to the a protective barrier against the external

surface of the membrane. environment.

Carbohydrates: Carbohydrates are

attached to the outer surface of the TRANSPORT MECHANISM

membrane, forming glycoproteins and

glycolipids.
Passive - do not require the cell to expend Homeostasis – internal balance of cells

energy

ACTIVE TRANSPORT
Simple Diffusion – movement of - Needs the use of energy
molecules/ions; high to low to achieve 2 main types (bulk transport)
equillibrium - Exocytosis - (exit) process of

expolsion
Osmosis – movement of water - Endocytosis – reverse process
Facilitated Diffusion – transport protein (enter)
Channel Proteins: Form pores or Results in the accumulation
channels

Carrier Proteins: Bind to specific BULK TRANSPORT

molecules -Vesicular transport

2 types of Endocytosis:
Equally divided – equilibrium Phagocytosis – cell eating
Semi-permeable Pinocytosis – cell drinking
Hypertonic Solution – dehydrated

“shrink” ENZYMES
Isotonic – in normal condition; biconcave;

has equal amount of water An enzyme is a biological catalyst, usually

Hypotonic; swell a protein, that speeds up specific chemical

reactions in living organisms. It works by

lowering the activation energy of a

reaction, allowing it to occur much faster

than it would on its own. Enzymes are not

consumed or permanently changed in the

reactions they catalyze, so they can be enzyme's active site, forming an enzyme-

used repeatedly. substrate complex. Enzymes are highly

specific, meaning each enzyme typically

Enzymes catalyzes a reaction involving only one or

a few specific substrates.

Enzymes are biological catalysts, typically

proteins, that speed up chemical reactions

Enzyme-Substrate Complex
within living organisms. They facilitate

reactions by lowering the activation The enzyme-substrate complex is formed

energy required for the reaction to occur, when the substrate binds to the enzyme's

without being consumed or permanently active site. This interaction is usually

altered themselves. stabilized by non-covalent interactions,

such as hydrogen bonds, hydrophobic

Active Site interactions, and ionic bonds. The

formation of the enzyme-substrate

The active site is a specific region on the
complex brings the substrate into the
enzyme where the substrate binds and
optimal orientation for the chemical
the chemical reaction takes place. It is a
reaction to occur.
three-dimensional pocket or cleft formed

by specific amino acid residues. The shape

Product
and chemical properties of the active site

are complementary to the substrate, The product is the result of the enzymatic

ensuring high specificity. reaction. Once the reaction is complete,

the enzyme releases the product(s), and

Substrate the enzyme is then free to catalyze

another reaction. The enzyme itself is not

A substrate is the molecule upon which an
altered by the reaction and can be reused
enzyme acts. The substrate binds to the
repeatedly.
Cofactors – typically metal ions (iron)

Coenzymes – organic molecules

(vitamins)

2 factors that affects enzymes:

PH – power of hydrogen

Temperature

Denatured – nasira ang shape; if its cold

Optimum – exact temparature

REDOX REACTION ;

1. Oxidation – loses electron –

positively charged cellular

respiration – glucose (sugar) - ATP

2. Reduction – gains electron