SPLASH class by Natalie Hollister

The Tiny Living World Around Us

For Starters

• My name is Natalie • Please feel free to ask questions• Let me know if I go too quickly or too slowly• Have fun!

What is a cell?

Think of cells as living bricks

• Bricks are the basic unit that some buildings are made of, cells are the basic unit that living things are made of• A house (organism) gets bigger when more bricks (cells) are added to

it• When a brick breaks (or a cell dies) it has to be replaced with a new

brick (cell)• Young humans grow because the number of cells being made

surpasses the number of cells dying

Different Types of Cells

Cells have organs just like human bodies do!• Except in cells we call them organelles• Nucleus, Golgi apparatus (Golgi body), smooth/rough endoplasmic

reticulum, ribosomes, lysosomes, mitochondria, cell membrane, chloroplast in plant cells, and others • A cell is eukaryotic if it has a nucleus (plant and animal cells)• A cell is prokaryotic if it does not have a nucleus (bacterial cells)• Red blood cells in our bodies are the weird ones – they have no

nucleus even though they are considered “animal cells”

Nucleus

• Like the “brain” of our cells• Tells the cells when to divide and tells the organelles what to do• Contains a nucleolus and is wrapped in nuclear envelope• Contains the genetic material that makes complex life possible

Mitochondrion

• Stores and releases energy in the form of ATP (adenosine triphosphate)• Has its own genetic material plus special enzymes and proteins

Endoplasmic Reticulum (smooth and rough)• Rough endoplasmic reticulum (sometimes abbreviated ER) has

ribosomes and is responsible for protein synthesis• Smooth ER has no ribosomes and instead performs lipid/carbohydrate

synthesis and buds off vesicles carrying proteins

Golgi Apparatus (or Golgi Body)

• Golgi body is like a UPS center• It packs different carbohydrates, proteins, and lipids into containers

called vesicles to be shipped to other parts of the cell• Named after its discoverer, Camillo Golgi

Cells communicate using genetic material• DNA – deoxyribonucleic acid• RNA – ribonucleic acid• In complex organisms, DNA is the genetic material that holds literally

everything about us• Simple organisms just use RNA• Not all cell organelles know how to use DNA, so DNA RNA

proteins in certain parts of a cell (transcription then translation)

More on DNA

• Shape is called a double helix• Chemically, a deoxyribose sugar is bound to a phosphate group and a

nitrogenous base (adenine, thymine, cytosine, or guanine)• Together the sugar, phosphate, and base make a nucleotide• When a bunch of DNA is put together it makes a chromosome

Cells divide to make new cells

• Unless a cell is a reproductive cell (egg or sperm) it will divide into two identical cells• Division process is called mitosis• It happens in four phases…more on next slide• When an egg or sperm divides, it uses a process called meiosis• Resulting cells are not identical

How can we look at cells?

• Most cells can be seen with microscopes• Basic microscopes have magnifying lenses that can let us see

microscopic cells/organisms• Really powerful microscopes let us see the small details of cells• Special microscopes or microscope slides can let us see things while

they are still alive

Some cells are bad for certain organisms• Tiny organisms (called microorganisms or microbes) live inside our

bodies and interact with our cells all the time• The good microbes are called normal flora• Some microbes make us sick and those are called pathogens• We categorize pathogens into three main areas: viruses, bacteria, and

parasites

Viruses – a subject of much debate

• Viruses are not technically living things• They can’t reproduce on their own (criteria of life is reproducibility)• They attack “host cells” and inject their RNA into them, then they can

reproduce inside the host cells• They are sub-microscopic (harder to fight with medicine)• Cold, flu, HIV, and right now Ebola

Bacteria

• Actual living things that are not sub-microscopic• They reproduce on their own and crowd out/kill our own cells when

they are inside us• We fight them with antibiotics• Note: antibiotics cannot kill viruses – only bacteria and some parasites

• There are also things called probiotics that help good bacteria live in our bodies (mostly in our digestive systems)• Strep throat, pink eye, some forms of meningitis

Parasites

• Typically multicellular organisms that attack a host• Often reproduce inside their host but on their own (unlike virus)• Some are single-celled organisms like amoebas• Some form protective coating called a cyst• Ticks, fleas, maggots, worms, amoebas, and plenty of others

How our bodies fight pathogens

• White blood cells are the soldiers of our body• When there is a pathogen they are alerted and they go to directly

take on the enemy and solve the problem• Some medicine can help the white blood cells if the pathogen is very

strong and the white blood cells can’t fight it alone• Skin is actually the first line of defense – wash those hands!

Different types of white blood cells

• Neutrophils – eat bacteria• Eosinophils – allergies and attacking multicellular parasites• Basophils – also allergies• Dendritic cells – marks pathogens with antibodies• Macrophages – big, tough cells that eat other big, tough cells• Lymphocytes – regulate the immune system

What your “blood type” means

• Antibodies mark pathogens once they are discovered in the body so the immune system can find and destroy them• We are born with or without certain sets of antibodies (A and B)• If you have type O, you have neither A or B antibodies • The plus or minus means you have/don’t have a certain protein• No blood type is better or worse than any of the others – we mostly

care about it because of blood transfusions

The good and bad of medicine

• Medicines, especially antibiotics, are good and help fight pathogens• Pathogens can mutate as a species over time though and become

immune to medications if they are used too often• These immune pathogens are called “superbugs” and are very hard to

kill (the most famous one is called MRSA)• Pathogens are becoming resistant faster than we can develop new

medications, so avoiding overmedication is important

Question Period