Cytology

Cytology• Cytology : study of the structure and

function of cells.

• Cytoplasm : area of space outside the nucleus; contains the organelles & cytosol.

• Organelles are tiny structures in the cytoplasm which perform various jobs for the cell.

• Cytosol is the fluid part of the cytoplasm.

Prokaryotic Cells• They lack a nuclear

membrane as well any other membrane covered organelles in their cytoplasm.

• Considered to be “Primitive Cells”

• Example : Bacteria & Blue-Green Algae

Eukaryotic Cells• They possess a

nuclear membrane as well as membrane bound organelles in their cytoplasm.

• Example : Plant & Animal Cells

The Nucleus• is the computer or control center of the

cell. • discovered by James Watson, Francis

Crick, & Rosalind Franklin (1953).• contains the genetic material of life

DNA (Deoxyribonucleic acid).• a DNA molecule consists of

nucleotides connected together.

NucleotideA nucleotide consists of a :

1. Phosphate group2. Deoxyribose sugar3. Nitrogen base: 4 types

Adenine (A)Thymine (T)Cytosine (C)Guanine (G)

DNA consists of two nucleotidechains connected together.

A & T always pair up, whileC & G do the same.

DNA Double Helix

DNA Replication

Nitrogen Bases

Replication Fork

DNA Polymerase

Replication Fork

Original strandNew Strand

Growth

Growth

• Long chains of DNA form Chromatin.

• Short sections of DNA along a piece of chromatin form Genes.

• A gene will either produce or influence a specific trait in the offspring.

Chromatin

Chromatin

Supercoils

Nucleosome

DNA double helix

Histones

Coils

• Nucleolus / Nucleoli (plural) : a dark spherical structure that is the site of ribosome formation.

• Ribosomes and other important chemical messages leave the nucleus through the Nuclear Pores. The membrane around the nucleus is called the Nuclear Membrane or Envelope.

Mitochondrion• Mitochondria (plural) : is a membrane

bound oval shaped organelle that function as the cell’s “power plant”.

• Creates the energy rich molecule called ATP (Adenosine Triphosphate).

• ATP is created through a process called Cellular Respiration which requires oxygen and therefore is an Aerobic process

Cellular RespirationC6H12O6 + 6O2 + enzyme 6CO2 + 6H2O + 36 ATP

Only eukaryotic cells have mitochondria. The Cristae (inner membrane with finger-like projections) have enzymes attached to them where cellular respiration occurs.

Mitochondria have their own DNA different from that of the nucleus. Biologists believe that a bacteria got trapped inside the early cell and evolved into this energy producing organelle. This mitochondrial DNA is very similar to bacterial DNA !

How do prokaryotic cells make ATP?

• They rely on a process called Fermentation.

• Fermentation is a simple Anaerobic (no O2) process that partially breaks down glucose to make SOME ATP.

• Example: Lactic Acid Fermentation which bacteria and humans perform.

Glucose + Enzyme Lactic Acid + 2 ATP

Chloroplast• Found only in plant cells.• Contain the green pigment chlorophyll.• They are involved with the process of

Photosynthesis which takes place within these Thylakoid Membranes.

Photosynthesis6CO2 + 6H2O + sun light C6H12O6 + 6O2

The glucose created from photosynthesis can now be broken down through Cellular Respiration to make 36 ATP.

Chloroplasts also have their own DNA ?

Plant Cell

Nuclear envelopeRibosome (free)

Ribosome (attached)

Mitochondrion

Golgi apparatus

Vacuole

NucleolusNucleus

Smooth endoplasmic reticulum

Rough endoplasmic reticulum

Cell wallCell membrane

Chloroplast

Animal CellSmooth endoplasmic reticulum

Ribosome (free)

Ribosome (attached)

Golgi apparatus

Mitochondrion

Rough endoplasmic reticulum

Cell membrane

Nucleus

Nuclear envelope

Nucleolus

Centrioles

Another Animal Cell

Plant & Animal CellSimulation

• Click on the title above and work through the plant and animal cell simulation.

Animal Cell Matching Activity• Click on the title above and it will lead

you to the animal cell website.

• Click on the “start activity” icon and let the fun start!

What’s The Difference?Animal Cell Plant Cell

Do not have a cell wall Possess a cell wall made of cellulose

Do not have plastids like chloroplasts

Possess plastids like chloroplasts

Possess centrioles used in cell division

No centrioles but can still do cell division

Possess small vacuoles

Possess large vacuole 90% of cell’s volume

Round to irregular in shape

Rectangular in shape due to cell wall