Unit 3: Cells

Cell Biology

Each of these images shows a cell from different parts of the body.  Can you identify which came from the:

1.  Muscle   

2.  Digestive system         

3.  Mouth

Cytology = the study of cells

All Animal Cells have 3 main parts

• Nucleus

• Cytoplasm (cytosol)

• Cell Membrane

All of the body’s functions are carried out by the cell, which are organized into tissues.

Case Study:

Mackenzie, at 4 years old, was diagnosed with pneumonia.   Her parents were worried, it seemed that Mackenzie was always sick.  She always had a runny nose and had frequent ear infections.    

The diagnosis of pneumonia also revealed something else - Mackenzie had a condition known as situs inversus. 

What do you think situs inversus is?   

Cells within your body vary in size, structure, and function.

They all start off the same way in an organism, but eventually

DIFFERENTIATE into specific types of cells.

Cell Membrane: (also called phospholipid bilayer) consists of phospholipids and embedded proteins.

The membrane regulates what enters and leaves the cell.  It is 

SELECTIVELY PERMEABLE.

The cytoplasm (cytosol) is the area between the nucleus and the membrane. (contains organelles)

Many of the cell’s metabolic reactions occur in this area.

ORGANELLES

"little organs" within the cell that perform specific functions

1. ENDOPLASMIC RETICULUM

Transport system; canals and channels that connect membrane to nucleus and to organelles within the cell

Function = transport system

Smooth ER  for lipid synthesis

Rough ER 

•  Has ribosomes on the surface

•  Ribosomes make protein

2. Golgi Apparatus

Function = package and delivery of proteins produced by the ribosomes

Proteins are exported in vesicles

3. Mitochondria

Chemical energy from food is converted to a usable form (ATP)  --   process is called Cellular Respiration

Cellular respiration requires glucose (food) and oxygen

Mitochondrial Disorders: When the mitochondria cannot produce enough ATP, cells lack energy to perform basic life processes.  

4. Lysosomes - contain enzymes to break down substances  (“suicide sac”)

Enzymes break down substances in the cell, such as food or worn out cell parts, even bacteria.

Lysosomal Storage Disorder: Tay Sachs - progressive deterioration of nerve cells and of mental and physical abilities that begins around 7 months of age and usually results in death by the age of four.

5. Centrosome (centrioles) – two cylinders; perpendicular
   During cell division, the centrioles form a spindle. 

The spindle moves chromosomes during cell division so that each new cell gets the proper number.

6. Cytoskeleton

made of microfilaments and microtubules for cell shape and support

Cilia and Flagella - both involved in movement

PRIMARY CILIARY DYSKINESIA = disorder causes cells to not create normal cilia.  

7. Nucleus -  (the “brain” of the cell) 

Directs cell activities (the “brain” of the cell)

Contains genetic information (DNA) in the form of chromatin

Nucleolus – responsible for the production of ribosomes

Has tiny pores in the nuclear membrane is where RNA can exit the nucleus

The Big Picture

The cell is like a factory. It makes a product, a PROTEIN, according to the instructions of the DNA. 

Each part of the cell has a job to do in this process. 

Movement of Substances Across the Membrane:

• Cells must bring in materials, like food and oxygen and remove wastes.

• These processes occur at the cell membrane.

• Cells are limited in size by the surface area (membrane) and volume (insides) ratio.

• Increasing surface area can increase the cell’s efficiency moving substances.

• Cells of the digestive system have projections called villi that aid in absorbing nutrients. 

Diffusion - molecules tend to spread out; moving from areas of high concentration to low concentration

This process requires no energy, it is called PASSIVE TRANSPORT

The Life Cycle of the Cell:

• Interphase = growth phase

• Mitosis = nuclear division

• Cytokinesis = cell splits into 2 daughter cells

The steps of mitosis ensure that each new cell has the exact same number of chromosomes as the original

The structure of a chromosome:

MITOSIS

 Interphase → Prophase →  Metaphase →  Anaphase →  Telophase

IPMAT

Interphase is part of the cell cycle, but mitosis begins with prophase

PROPHASE:

1. chromosomes visible 

2. centrioles move to poles

3. nuclear membrane disappears

4. nucleolus disappears

5. spindle forms

METAPHASE:

chromosomes line up on the equator

ANAPHASE

chromatids separate and move to opposite poles

TELOPHASE

1. chromosomes disappear 

2. nuclear membrane reforms

3. nucleoli reappears

4. spindle disappears

5. centrioles duplicate

Cytokinesis = Cell splits into two daughter cells

Cancer is essentially a disease of mitosis - the normal 'checkpoints' regulating mitosis are ignored.

This causes uncontrolled cell division.

Changes in DNA (mutations) cause checkpoints to be ignored. 

APOPTOSIS = programmed cell death

Damage to DNA  at a checkpoint can signal a cell to self destruct. 

• Cancer:  caused by uncontrolled cell division

Cervical cancer and HPV:

Many strains of HPV (human papillomavirus) causes warts, both on the hands and on the genitals. 

The virus causes the cells to mutate and increases the risk of cancer.

There is a vaccine for the form of HPV that can cause cervical, throat, and anus cancer!

HeLa Cells:

HeLa cells are named for cells that were obtained from a woman named Henrietta Lacks in 1951.

Henrietta died of cervical  cancer, but the cells harvested from the cancer tumor are used in research today - they are considered an IMMORTAL LINE

Hela cells were used to develop polio vaccines, they have been sent into space, they are used in HIV/AIDs research.

Basically any scientists wanting to study human cells to test pharmaceuticals is probably working with HeLa cells.

Why are they immortal?

• These cells do not die after a set number of cell divisions.  This is a property known as senescence.   Researchers can keep cultures of these cells indefinitely. 

• This makes them very valuable for research purposes!

Was it ethical?

Henrietta Lacks died at the age of 30, never knowing her cell line would continue on in research.