Cell Biology and Techniques

CELL

Dr. Hajira Siddique, a Biochemistry professor, talks about how our bodies break down food and about cell biology.

CELL THEORY

All living things are made of cells (cells are the basic parts of life).

Cells are the smallest working parts of living things (they do jobs like growing and getting energy).

Cells only come from other cells (they don't just appear).

Cells have DNA, which is like a set of instructions (DNA tells cells what to do).

LEARNING OBJECTIVES

Cell Theory

Types of cells: Prokaryotic and Eukaryotic

Cytology: How we study cells

What these cell parts do:-

Nucleus (the cell's control center, holds DNA)

Golgi apparatus (packages and ships things in the cell)

Mitochondria (makes energy for the cell)

Ribosomes (build proteins)

Endoplasmic reticulum (helps make proteins and fats)

MAJOR DIFFERENCES BETWEEN PROKARYOTIC AND EUKARYOTIC CELLS

Eukaryotic Cell:- DNA is inside a nucleus (a special room in the cell).

Prokaryotic Cell:- DNA is just in one area (called the nucleoid).

PROKARYOTIC AND EUKARYOTIC CELLS - Similarities

All cells have these things:-

A plasma membrane (outer covering that holds the cell together)

Cytosol with organelles (the cell's fluid with tiny parts)

Chromosomes (contain DNA)

Ribosomes (make proteins)

Major differences… Cytoplasm

Prokaryotic cell: Everything inside the plasma membrane is cytoplasm.

Eukaryotic cell: The cytoplasm has different parts called organelles (each does a special job).

Size

Eukaryotic cells are usually bigger than prokaryotic cells.-

Smallest bacteria, mycoplasmas

Eukaryotic cells are typically $0.1$ to $1.0$ micron

$10-100$ microns in diameter (most bacteria: $1-10$ microns)

SUBCELLULAR FRACTIONATION

Two steps:

2. Break the tissue or cells to release parts.

3. Separate the parts using special machines.

CYTOLOGY

Studying cells. We look at how they're built and what they do.

We use different ways to take apart the cell.

We study how cells are built and what they do.

5. HOMOGENIZATION

Ways to break cells:

Sonication (using sound waves)

Chemical Lysis (using chemicals)

Enzymatic Lysis (using enzymes)

a. SONICATION

Sound waves break open the cell and let out what's inside.

Works well to break cells.

Good for getting proteins out of cells.

b. CHEMICAL LYSIS

Surfactants: Break down fats in the cell covering (like soap).

e.g., sodium sulfonate, sodium dodecyl sulfate (SDS)

Alkali: Break down the cell covering.

e.g., sodium hydroxide

Organic solvents: Go into the cell and make it swell.

e.g., toluene

c. Enzymatic Lysis

Using enzymes to break cells. Enzymes are like helpers that speed up the breakdown.

Such as:-

Lysozyme: Breaks down bacteria.

Zymolase: Breaks down yeast.

Cellulase: Breaks down plant cells.

Protease: Breaks down proteins.

glycanase: Breaks down sugars.

The good thing about using enzymes is they are specific (they only break certain things).

6. CENTRIFUGATION

Spinning a mix of cell parts to separate them by weight (heavy stuff goes to the bottom).

DENSITY GRADIENT CENTRIFUGATION

Using a sugary liquid to separate cell parts by size and weight (parts move to where they fit best).

DIFFERENTIAL CENTRIFUGATION

First, filter out big chunks. Then, spin the mix at different speeds to separate parts:-

$600g$ x $10$ min: Nuclei

$15,000g$ x $5$ min: Mitochondria, chloroplasts

$100,000g$ x $60$ min: Ribosomes, peroxisomes. Plasma membrane, microsomal fraction (fragments of endoplasmic reticulum), and large polyribosomes

$100,000g$ x several hours: Ribosomal subunits, small ribosomes, Soluble part of Cytoplasm (cytosol)

BIOMARKER ENZYMES

Cell parts and their special markers: