M1B: Topic 5 - Cell Biology

The Cell is…

The fundamental unit of life

Every form of life on Earth is..

a cell or is composed of cells

Rule for Cells:

Cells can only come from other cells

Unicellular

Made up of one cell

Multicellular

Made up of more than one cell (2+)

What do we use to look at cells?

A light microscope

All cells have..

1. Plasma Membrane

2. Cytoplasm

3. DNA

4. Ribosomes

Prokaryotic Cells

“before the nucleus”

no nucleus or membrane bound organelles

Small cells that can rapidly divide

Prokaryotes are single celled ONLY

• Example: bacteria

Eukaryotic Cells

“A true nucleus”

Large, complex cells with internal membrane -bound organelles

Eukaryotes can be either single cellular OR multicellular

• Protists, fungi are unicellular

• Plants and animals are multicellular

Multicellularity allows for organism complexity

Anatomy of an animal cell

Plasma membrane

• no cell wall

• Nucleus

• Houses DNA

• Site of transcription

• Endomembrane System

• site of protein synthesis,

processing, and transport

• Cytoskeleton

• Maintains cell shape and

organization

• Mitochondria

• Energy production

Anatomy of a plant cell

Largely similar to animal cells

• Some differences

• Cell wall made of cellulose

• Provides structure and shape

• Protects against osmotic lysis

• Central Vacuole

• Nutrient storage

• Waste management

• Predator deterrence

• Pigment/ Sexual reproduction

• Physical support

• Chloroplasts

• site of photosynthesis

Osmotic lysis (hypoosmotic)

No cell wall

Osmotic lysis (hypotonic)

Cell wall

Organelles

Eukaryotic cells have organelles

• Small, membrane bound

structures within a cell that have

distinct functions

• Organelles can work together to

perform the functions of the cell

• Organelle Systems

The Endomembrane System

Purpose: make, modify, package,

and transport proteins & lipids

• Includes:

1. Nucleus

2. Endoplasmic reticulum

(rough)

3. Golgi apparatus

4. Vesicles

Central Dogma of Biology

DNA encodes instructions for

making proteins

• Transcription: DNA serves as a

template to synthesize RNA

• Translation: RNA serves as

instructions to make protein

The Nucleus

Houses the DNA

• Has two phospholipid

bilayers - why?

• Site of RNA synthesis from

DNA (Transcription)

• Once RNA is made it leaves

the nucleus and goes to

the...Endoplasmic Reticulum (Rough)

(Rough) Endoplasmic Reticulum

Site of protein synthesis

• using RNA as instructions

• The rough endoplasmic reticulum

has ribosomes attached to it

• Ribosomes: Assemble amino acids

into a polypeptide chain

• polypeptide chain then folds

into a protein (2° and 3°

structure)

• Once the protein has been made it

goes to the...

Golgi Apparatus

The golgi apparatus sorts, tags,

packages, and distributes the

proteins

• Makes sure they get where they

are supposed to go!

• How do they get there?

• In a vesicle!

Vesicles

Vesicles are membrane-bound

sacs that transport things

(proteins) where they need to go!

Some other organelles

Both plant and animal cells (eukaryotic

cells) have many organelles

• A couple more we will look at are:

• Mitochondria

• Lysosomes

• Central Vacuole

• Chloroplast

Mitochondria

• The “powerhouse” of

the cell

• Site of ATP synthesis

• Cellular energy

• Cells that need more

energy will have more

mitochondria

Lysosomes

The cell’s “stomach”

• Lyse ingested cells

• Digests contents

Plant cells also have..

Central Vacuole

• Nutrient storage

• Waste management

• Predator deterrence

• Pigment/ Sexual reproduction

• Physical support

Plant cells also have..

Chloroplasts

• Perform photosynthesis

• Site of photosynthesis

• Contains a green pigment–

chlorophyll– captures energy of

sunlight