BIO1 - L1&2

Cell Theory & Structure, Cell Cycle

Robert Hooke

• Observed thin slices of cork using a compound microscope

• Saw a small box-like structures

Robert Hooke

SCIENTIST: Named them “cells” because they resembled small room

Zacharias Janssen

SCIENTIST: Invented the first compound microscope

Antoine Van Leeuwenhoek

scientist: Built powerful single-lens microscopes

Antoine Van Leeuwenhoek

scientist: First to observe living cells like protozoa, spermatozoa & bacteria

Matthias Jacob Schleiden

scientist: Studied plant tissues

Matthias Jacob Schleiden

scientist: Proposed that all plants are composed of cells, which helped establish the idea that living organisms are made up of cells

THEODORE SCHWANN

WHO SAID: “ALL LIVING THINGS ARE MADE OF CELLS“

Rudolf Virchow

• Used microscopic observations to understand how cells develop and reproduce

• Proposed that new cells arise from existing cell

Rudolf Virchow

Father of Cellular Pathology

GALILEO GALILEI

INVESTED THE FIRST MICROSCOPE

RUDOLF Virchow & MATTHIAS Schleiden

WHO SAID: “Cells are basic unit of life“

RUDOLF Virchow

WHO SAID: “Cells come from pre-existing cells that have multiplied“

1. The cell is the fundamental unit of structure and function in living things.

2. All organisms are made up of one or more cells.

3. Cells arise from other cells through cellular division.

4. The energy flow occurs within cells.

5. The cellular constituents are similar amongst the various individuals of similar species.

6. Cells carry genetic information that is passed to daughter cells during cell division.

six postulates of the modern cell theory??

• Discovery of cells

• Understand cell structure & function

• Advance medicine & disease study

• Discover microorganisms 

• Grow scientific research & technology

5 IMPORTANCES OF MICROSCOPE

• OCULAR LENS

• BODY TUBE

• REVOLVING NOSEPIECE

• OBJECTIVES

• STAGE CLIPS

• DIAPHRAGM

• LIGHT SOURCE

• ARM

• STAGE

• COARSE ADJUSTMENT KNOB

• FINE ADJUSTMENT KNOB

• BASE

12 PARTS OF A MICROSCOPE?

Light Microscope

• Easy to operate, less expensive

• Can observe live specimen

• Produce colored images

• Lower magnification

Electron Microscope

• Greater magnification & resolution

• Can reveal organelles in detail

• Expensive equipment

• Specimens must be dead

1. Place the slide on the stage and secure it.

2. Start with the low-power objective.

3. Look through the eyepiece and use the coarse knob to find the specimen.

4. Use the fine knob to make the image clear.

5. Switch to high power if needed, and use only the fine knob to refocus.

How to use the microscope?

CELL

structural, functional, and biological units of all living beings. Can replicate itself independently. Hence, they are known as the building blocks of life

• Pro - Before

• Eu - True

• Karyon - Kernel

Meaning of “PRO“ in prokaryotic & “EU“ & “KARYON“

Prokaryotic

Unicellular organisms w/o a nucleus & nuclear-bound organelles; therefore, all reactions occur within the cytoplasm 

Prokaryotic

This cell only has nucleoids

Prokaryotic

DNA is curled up in the cytoplasm

Eukaryotic

multicellular organisms that have nucleus and membrane-bound organelles

Eukaryotic

cell that is generally larger & more structurally complex

Eukaryotic

WHAT CELL: Membrane-bound, DNA has a boundary

plant, animal, fungi, protista

example of eukaryotic cells

• To function simply

• To reproduce rapidly (binary fission)

• To be more efficient in nutrient exchange within their environment (surface area) 

Why are prokaryotic cells smaller than eukaryotic cells, and why are they unicellular?

Prokaryotes: Bacteria Cell

one of the most ancient group of living organism

ability to survive, pathogenicity, and attachment to surfaces

importance of bacterial shape

rod-shaped (BACILLI) BACTERIA

blabla-shaped bacteria have more surface area, which allows nutrient uptake for growth

spherical (COCCI) BACTERIA

blabla-shaped bacteria have less surface area, which helps them survive in harsh environments

Spiral-shaped BACTERIA

blabla-shaped bacteria are often better at moving through viscous environments

Cluster/chained bacteria

blabla-shaped bacteria are more difficult to clear (phagocytosis)

thermophiles, mesophiles, psychrophiles

3 classifications of temperature-based bacteria?

thermophiles (40-100)

this type of bacteria has modified lipid compositions (longer lenghts of lipid acyl chains) in a liquid crystalline state

psychrophiles (0-20)

this type of bacteria has specialized membranes and energy-generating systems, and secretes cold shock proteins that enable specific activities

GRAM POSITIVE

Bacteria Gram Stains: Thick peptidoglycan and has lipoteichoic acid spikes

GRAM NEGATIVE

Bacteria Gram Stains: BALANCED OUTER MEMBRANE, PEPTIDOGLYCAN

LPS (Lipopolysaccharide)

• causes toxins & serious infections

• present in bacterial cell wall that contributes to the integral structure of the bacterial cell

• protects the cell from chemical attacks

• bacterial surface adhesion

absorbs antibiotics and cleaning products

why is gram-positive easier to kill?

Animal Cells

• Do not have cell wall

• Have the ability to perform phagocytosis and pinocytosis

Plant Cell

• The cell wall has cellulose 

• A large vacuole, which maintains the turgor pressure

• Has chlorophyll

Yeast Cell (Fungal)

• Cell wall has chitin

• Some have holes known as septa

• PLANT HAS CELL WALL, CHLOROPLAST, LARGE CENTRAL VACUOLE

DIFFERENCE OF PLANT AND ANIMAL CELL

Centrioles

Organize the microtubules to form spindle fibers that pull the chromosomes

Nucleus

Houses the DNA which holds the genetic information of the cell

Chromosome

Coiled and organized DNA with histones

1. New skin cells (they’re near blood vessels because they need the nutrients)

2. Coming to surface

3. Degeneration process

4. Dead skin cells

Skin Cells Life Cycle?

Cell Cycle

It is the series of stages that a cell goes through as it grows, copies its DNA, and divides into 2 daughter cells

• Grow by increasing the number of cells

• Repair damaged tissues by replacing damaged or dead cells

• Replace old cells with new ones

• Reproduce in organisms that reproduce through cell division

• Maintain genetic continuity by ensuring that DNA is copied and distributed to daughter cells

IMPORTANCE OF CELL CYCLE

Interphase

Longest period where metabolic processes take place

G1 PHASE

• Cells grow in size.

• Cell organelles and proteins are produced.

• High metabolic activity

G1 PHASE

• Prepares machinery for DNA replication

• Decision point: divide or enter G0 (quiescence)

S PHASE

DNA is synthesized & replicated

S PHASE

• Chromosomes are replicated.

• Histone production increases

• Centrosome duplication continues

• Chromatin remains loosely packed

G2 PHASE

• Extensive synthesis of organelles.

• Cells grow more

• Synthesizes proteins required for mitosis (e.g. tubulin) 

• Checks DNA integrity

G2 PHASE

Prepares for chromosome condensation and spindle formation

removes damaged or unnecessary cells, maintaining tissue health and preventing the spread of harmful cells

IMPORTANCE OF APOPTOSIS

Stimulating proteins (Go)

encoded by proto-onconogenes

Inhibitory proteins (Stop)

encoded by tumor suppressor genes

CDKs Cyclin-dependent kinases

Stimulates the cell cycle

Checks whether the cell is big enough and has made the proper proteins for the synthesis phase

CHECKPOINT IN G1?

p53 Protein

G1: Stops the progression to S-phase if DNA is damaged, following apoptosis

Retinoblastoma protein (Rb)

G1: Prevents cell from entering S-phase

ATM Protein (ataxia telangiectasia mutated protein)

S: if DNA is damaged, it halts the cell cycle & activates proteins for DNA repair (leukemia, lymphoma)

Wee 1 kinase

G2: Inhibits CDK 1

p53 Protein

G2: Stops the cell cycle progression until the damage is repaired, otherwise leading to apoptosis

APC (Anaphase-promoting complex)

M: Inhibits progression to Anaphase when chromosomes are not properly attached to spindle fibers

APC (Anaphase-promoting complex)

M: Destroy the proteins that bind sister chromatids in preparation to anaphase

• Checks, whether DNA has been replicated correctly

• If so, the cell continues on to mitosis

checkpoint in S PHASE?

• Occurs during the mitotic phase (premetaphase)

• Checks where all the chromosomes are attached and under bipolar tension

• If so, the cell divides, and the cycle repeats

CHECKPOINT IN M PHASE?

• LOSS OF CHECKPOINT CONTROL

• OVERACTIVE ONCOGENES

• INACTIVATION OF TUMR SUPPRESSORS

• FAILURE OF APOPTOSIS

Cancer can result from disruptions in the regulation of the cell cycle, often due to mutations in the genes that control key checkpoints or repair processes. These mutations can cause:

CENTRIFUGAL

Cell plate appears in the middle

Somatic (diploid)

• product of mitosis

• body cells

• contain 2 complete sets of chromosomes

•  46 chromosomes

HEx Cells (haploid)

• product of meiosis

• contain only 1 set of chromosomes

• 23 chromosomes

Interphase takes 18-20 hours

Where do cells nost of its time?

No, it depends on the type of cel

Do all cells divide at the same rate?

GROW, REPAIR DAMAGE TISSUES, REPLACE OLD CELLS, REPRODUCE, MAINTAIN GENETIC CONTINUITY

CELL CYCLE IMPORTANCE