Cells 
Overview of Cellular Basis of Life
Late 1800 Robert Hooke was looking through a microscope at some plant tissue and cork
What he saw was some cube like structures that reminded him of the long rows of monks rooms (or cells) at the monastery, so that is how the name “cells” got Hooked and is still around today!
Since the late 1800s cell research has been going on and has provided us with the cell theory:
A cell is the basic structural and functional unit of living organism. So when we define cell prosperities we are in fact defining the properties of life
The activity of an organism depends on the collective activities of its cells
According to the principle of complementarity , the biochemical activities of cells are dictated by the relative number of their specific subcellular structures
Continuity of life has cellular basis
Cells are formed from chemicals and structures
Cells are found in all living things
Some a single cell
Some nerve cells can be 2 feet long or longer
Cells can be flat, round, thread like, or irregularly shaped
7.5 trillion cells found in body work together to allow for proper functioning of body
Often referred to as the building blocks of our bodies
Cell Structure 
Certain common traits that almost all cells share:
Nucleus 
Organelles
Cytoplasm 
Cell membrane 
Organelles are made of even smaller substances called atoms
Atoms are tiny building blocks of all matter
Atoms combine to form molecules like water, sugar and proteins
These molecules build the cellular structures and facilitate the cell functions
There are four basic types of molecules found in cells:
Proteins
Carbohydrates
Lipids
Nucleic acids
Defined boundary that possesses a definite shape but flexible and actually holds cell contents together, acting as protective covering
Allows material in and out of cell
Selectively permeable or semi permeable because they choose what gets in or out
Has identification markers that identify it as coming from a certain person
Like a certain person come from PA (identification marker) that tells us Pittsburg PA is in Pennsylvania
3/10,000,000 of an inch thick
Selective permeability is only promising on a healthy, unharmed cell. When a cell dies or is badly damaged, its plasma membrane can no longer be selective and becomes permeable to nearly everything.
We see this problem when someone is badly burned
Precious fluids, proteins and ions “weep” (leak out) from the dead damaged cells.
Transport Methods
Moving things in and out of cell can be done in two broad ways:
Passive transport: requires no extra form of energy to complete
Like a yo-yo simply falling as it unwinds from a string
Active transport: requires some addition of energy to make it happen
Passive transport can be divided into four types:
Diffusion 
Osmosis 
Filtration 
Facilitated diffusion 
Most common form of passive transport in which substance of higher concentration travels to area of lesser concentration
The difference between these two concentrations is called the concentration gradient
Examples:
Adding packet of powdered drink mix to pitcher of water
Water gradually assumes the color and flavor of the powder
Smell of classmate’s perfume filling room
The smell diffuses from high concentration on the individual to low concentration throughout the room
Necessary to move oxygen from lungs to blood stream, or carbon dioxide from blood stream to lungs
Another form of diffusion in which water travels through selectively permeable membrane to equalize concentrations of a substance
Dissolved substance called a solute
Water tends to travel across a membrane to equalize concentrations of a solute; ability of substance to pull water toward area of higher concentration called osmotic pressure
The greater concentration of solute, the greater osmotic pressure, or pull, it exerts to bring in water
Differs from osmosis in that pressure is applied to force water and its dissolved materials (solutes) across or through a membrane(capillary wall) by fluid or hydrostatic pressure
Similar to a crowd of people being pushed through the turnstiles during rush hour
Effect you get when you squeeze the trigger on a squirt gun.
Major supplier for forces in body is pumping of heart, which forces blood flow into kidneys, where filtration takes place
Like diffusion, filtration is a passive process and a gradient is involved. The gradient is called a pressure gradient (actually pushes filtrate from high pressure to low pressure area
Facilitated diffusion (carrier mediated passive transport)is a variation of diffusion in which a substance is helped in moving across the membrane, similar to an usher helping you to your seat
Glucose is the substance that is often helped across a cell this way.
These carriers are very specific meaning only glucose can be carried by its special carrier
How is this passive transport then?
Think of it as a situation that glucose was already moving in an attempt to get across the cell and it has encountered an already revolving door
- once it steps into the door it is pushed along
Pathology Connections
Cystic fibrosis 
Incurable, fatal genetic disease affecting 1/3000 Caucasian babies
Caused by malformation in membrane channels for chloride and sodium ions
Sodium and chloride do not diffuse across cell membrane as they normally would because these channels are not normal.
Fluid around cells becomes extremely salty due to excess sodium and chloride which then ….
Results in excessively thick mucus in respiratory, digestive, pancreas especially) and reproductive systems; mucus can cause clogging in organs
Symptoms may include
Difficulty breathing (lungs appear normal at birth, but soon after birth obstruction of the airways with viscid mucus that leads to infection and a chronic inflammatory process)
Nutritional deficits due to decreased absorption of nutrients (failure of the pancreas to secrete enzymes ) will have excessive fat and protein in the stool) Missing lipase amylase, and trypsin (necessary for the breakdown and digestion of fat.
Increased risk of respiratory infection
As the thick mucus accumulates, obstruction occurs and the flow of air is impaired with an increase in residual volume and a decrease in the vital capacity of the lungs. The alveoli become overaerated and the chest distends, giving the appearance of a barrel shaped chest- impaired long enough, clubbing of fingers, cyanosis. Major problems include hemoptysis, Pneumothorax, cor pulmonale, respiratory failure and congestive heart failure
Diabetes failure of the pancreas working correctly
Infertility (especially in males)- the epididymis, vas deferens, and seminal vesicles are usually poorly developed or absent . Female fertility is low owing to plugging of the cervix with a thick mucus that is abnormal in physical and chemical properties that blocks the entrance of sperm
Diagnosis
Prenatal genetic testing
Postnatal genetic testing
Testing pulmonary function
Testing amount of sodium in sweat- this is called the pilocarpine test. Usually done after at least one month of age.
when you have a new born taste them and see if they taste salty.
Treatment
No cure; treatments help extend and improve quality of life (want the patient living an independent life
With treatment today, average life span of patient is 35 years
Antibiotics to prevent pneumonia- therapy aims to clear secretions fro the airways . Chest physical therapy (CPT), (percussion) breathing exercises, inhalation therapy, and antibiotics
Mucus thinning drugs - inhalation therapy liquefies the mucus, postural drainage
Nutritional supplements (pancreatic enzyme replacement, diet adjustment, and fat soluble vitamin supplementation. Salts is allowed in generous amounts to prevent depletion through sweating)
Diabetes mellitus 
Common medical problem; main symptom (high blood sugar) caused by problem with facilitated diffusion
Glucose transported into cells via facilitated diffusion with diabetes glucose cannot get into the cells
Hormone insulin must be present in order for transport of glucose to occur
Insulin is either absent, or cells insensitive to insulin (Insulin usually refereed to as the key to the door)
How does the body become insensitive to insulin?
Results in glucose not getting to cells like it should
Lack of glucose transport into cells causes several problems
Lots of glucose hangs around in bloodstream, causing big osmotic problems for cells
Cells can’t make as much energy as they need when glucose can’t be transported and it causes big health problems
Can be broken down further to three different types:
Active transport pumps 
Endocytosis 
Exocytosis 
Require addition of energy in form of ATP (adenosine triphosphate) to move substance
Energy needed because cell is trying to move substance into area that already has high concentration of substance
Example: need to transport potassium into our cells, where high concentration already exists; it must be “pushed” in
Used by cells for intake of liquid and food when substance too large to diffuse across membrane
The cell membrane will actually surround the substances with a small portion of its membrane, forming a chamber or vesicle, which will then separated from the membrane and move into the cell (phagocytosis).
This is what a WBC will do to bacteria to prevent infection
When done to a liquid it is called pinocytosis.
Transport of things out of cell
Some cells produce substance needed outside cell
Once substance is made, it is surrounded by membrane, forming a vesicle,(sac or bladder) and moves to cell membrane
Vesicle becomes part of cell membrane and expels its load out of cell
Exocytosis is a means by which the cells actively secrete hormones, mucus, and other cell products or eject certain cellular wastes
Familial hypercholesterolemia 
Condition in which blood cholesterol too high; caused by poor diet and exercise or inherited
Normally low density lipoprotein (LDL or “bad cholesterol”) binds to cholesterol, and allows it to be carried into cells via endocytosis; once inside, cholesterol used to make other lipids
In familial hypercholesterolemia, LDL doesn’t move into cells, and stays in blood; causes two problems
Too little cholesterol gets into cells, and cells must make more cholesterol
LDL that cannot get into cells hangs around in blood; causes plaques in blood vessels which can lead to blood clots, strokes, and heart attacks
Severe form of familial hypercholestrerolemia
Patients often have heart attacks or strokes as children
Often fatal in children or teenagers
Has no effective treatment
Moderate form of familial hypercholestrerolemia
Leads to heart attacks and strokes, but usually not until mid-life
Can be treated with diet modifications and cholesterol lowering drugs
Estimated that 1/500 Americans have moderate form
Gel-like substance composed of water, nutrients, and electrolytes, which looks a lot like white of raw egg
Required by cells for their internal environment in order for parts of cell, known as organelles, to thrive and function
"Brains” of cell (book describes it as city hall)
Dictates activities of other organelles in cell
Much like City Hall dictates the activity of the city departments
Has double walled nuclear membrane with large pores allowing certain materials to pass in and out, while preventing other materials from entering ( metal detectors at city hall)
Chromatin (bumpy loose threads)
Material found in nucleus that contains deoxyribonucleic acid (DNA); DNA contains blueprints, or specifications, for creation of new cells
Will eventually form chromosomes, which contain genes
Genes determine our inherited characteristics
Nucleolus 
Spherical body made up of dense fibers found within cell nucleus
Major function is to synthesize/create ribonucleic acid (RNA) that forms ribosomes
Ribosomes 
Made of ribonucleic acid (RNA) and assist in production of enzymes and other protein substances needed for cell repair and reproduction. It is the actual site for protein synthesis in the cell
Can be considered “remodeler” of cell, taking existing structure and maintaining and repairing
Organelles found on endoplasmic reticulum or found floating around in cytoplasm
Centrosomes 
Act as building contractor, building new structures as need arises
Specialized regions that contain centrioles that are involved in division of cell
Centrioles are tubular shaped and usually found in pairs
Mitochondria 
Tiny bean-shaped organelles, act as power plant to provide up to 95% of bodies’ energy needs for cellular repair, movement, and reproduction
If cell needs more power, it increases number of mitochondria in cell
Liver cells, which are quite active, have up to 2,000 mitochondria in each cell
Contain special enzymes that help to take in oxygen for use in producing energy
Energy produced is in form of ATP (adenosine triphosphate) created by mitochondria
Endoplasmic reticulum 
Series of channels set up in cytoplasm that are formed from folded membranes
Has two distinct forms:
One has sandpaper-like surface, with ribosomes on it, called rough endoplasmic reticulum; responsible for synthesis of protein
Second form has no ribosomes and appears smooth, called smooth endoplasmic reticulum; synthesizes lipids and steroids
Golgi apparatus 
Looks like a bunch of flattened membranous sacs
Once protein from the endoplasmic reticulum is received, it further processes and stores it
Takes processed protein to cell membrane where it is released Salivary glands and pancreatic glands have higher numbers of Golgi apparati because they have higher level of secretion or storage
Lysosomes 
Organelles containing powerful enzymes that take care of cleaning up intercellular debris and other waste
Lysosomes help keep us healthy; they destroy unwanted bacteria by participating in process of phagocytosis
Vesicles: can be thought of as little vans; they can be loaded up with substances and travel to other sites within cell
Cytoskeleton: network of microtubules and interconnected filaments that provide shape to cell and allow cell and its contents to be mobile 
Flagella: whip-shaped tails that move some cells, like sperm, to other locations 
Cilia: short, microscopic, hair-like projections located on outer surface of some cells; move particles using wavelike motion
Organelle disorders
An organelle can malfucntion here are a few:
Lysosomal storage disorder
Occur when lysosomes missing one of their enzymes. When an enzyme is missing or broken
Results in some molecules not breaking down and accumulating in cells
Many kinds of lysosomal storage disorders (40 )
All are genetic
Most lack effective therapies
Tay Sachs
Most common in Jews of central and eastern Europe descent
Enzyme missing in lysosomes of nervous system cells
As result, glycoproteins accumulate in cells in nervous system
Build up causes inflammation and eventual cellular destruction
Symptoms include mental regression, dementia and paralysis appearing within first year of patient’s life
Diagnosis: appearance of cherry red spot on back of patient’s eyes; abnormalities in startle reflex
No treatment; disease generally fatal within two or three years of onset
Availability of genetic test has decreased incidence in recent years
Cigarettes and paralyzed cilia 
Smoking causes cilia in respiratory tract to become paralyzed
As a result, cannot keep lungs clean
Over time, can lead to chronic obstructive pulmonary disease (COPD) and other smoking-related lung problems
Passive smoking (second hand smoke exposure) also increases risk of lung problems
Cell energy and ATP: energy molecule
Digestion breaks food down, releasing energy
In order for cells to use energy, nutrients must be converted to ATP, an energy transfer molecule
ATP made up of base, sugar, and three phosphate groups
Phosphate groups held together by high-energy bonds
Energy released each time bond is broken, turning ATP to ADP (two phosphate groups)
ADP can then pick up another bond, storing more energy, so process can begin again
Cells produce ATP through process called cellular respiration
In cellular respiration, glucose (from food) is combined with oxygen
Chemical reaction results in production of ATP in mitochondria
Also produces two waste products: water and carbon dioxide
Breathing (exchange of oxygen and carbon dioxide) provides necessary materials for cellular respiration
Oxygen breathed in to be combined with glucose (from food) to produce ATP
Carbon dioxide breathed out to rid body of chemical waste product generated by ATP production
Body begins to break down tissues like muscle in order to get energy from alternate sources such as fats and proteins; causes abnormal body chemistry
Excess glucose in blood causes problems
Abnormal concentration gradient develops between inside and outside of cells
Body tries to rid extra glucose by filtering extra blood through kidneys
Kidneys produce excessive amounts of urine, leads to water loss and possible dehydration
Lack of cellular glucose uptake and body’s attempts to compensate for high blood sugar lead to classic symptoms
Weight loss: cells cannot effectively use glucose from food patient eats
Excessive urination: body increases blood flow to kidneys in attempt to normalize excessively high blood sugar
Excessive thirst: patient dehydrates from excessive urination
May cause development of long-term problems, such as heart disease and kidney failure
Two types
Type 1 diabetes (formerly IDDM - insulin dependent diabetes mellitus); auto-immune disorder
Immune system attacks and destroys cells in pancreas that make insulin resulting in cessation of insulin production
Type 2 diabetes (formerly NIDDM - non-insulin dependent diabetes mellitus)
Develops when cells stop responding (insulin resistance); insulin still produced by pancreas, but tissues don’t respond
Usually related to obesity; associated with high cholesterol, high lipids and high blood pressure
Treatment depends on type of diabetes
Type-1 diabetes: not curable
Can be treated with daily insulin injections
Patients must adhere to strict diet
Type-2 diabetes: can sometimes be reversible
First step of treatment includes adoption of healthy diet & exercise habits and weight loss
Medications affecting pancreas or tissues can improve blood sugars
Some patients eventually require supplemental insulin
Enzymes
In order for your cells to be able to do anything, some chemicals need to be broken down and others need to be made.
Problem is the reactions tht are needed are reactions that take time (it is a slow process)
To solve the slowness problem, cells have special proteins
Enzymes (speed up the rate of a chemical reaction)
Facilitate important chemical reactions in body
One way is by speeding up reactions ( I did just say that so it must be important!!)
Not used up by reactions that they facilitate; instead, act like carrier molecules
Very specific; each only facilitates (catalyzes) certain reactions
Phenylketonuria
Genetic condition; enzyme disorder (both parents must be a carrier)
Most common in Caucasians of Irish, Scottish, or Scandinavian descent
Patients missing enzyme: phenylalanine hydroxylase (FENAL AL LA NEENE)
Without enzyme, amino acid phenylalanine builds up in cells
Build up affects nervous system; causes progressive mental retardation if not treated
Other signs include
Light pigmentation of skin, hair and eyes (inability to produce melanin)
Abnormalities of posture and gait
Epilepsy
Musty odor created by the excretion of phenylalanine metabolites in the urine and sweat
Behavioral problems can occur (hyperactive, agitated, aggressive)
Treatment: is aimed to balance the amino acids needed for growth and development against the dangers of amino acid accumulation
low phenylalanine diet includes avoidance of high protein foods and products sweetened with aspartame (NutraSweet™)
Consequences of going “off diet”
Children: cognitive defects
Adults: depression, anxiety, or other neurological changes
Diagnosis
Blood tests & genetic tests
Guthrie test (few drops of blood required) 72 hours to 7 days after birth
Every newborn in US routinely screened
Cell Cycle 
Two major phases of an eukaryotic cell’s life known as the cell cycle
When cell needs to reproduce, enters mitotic phase (actual cell division)
Mitotic phase divided into two major portions: mitosis and cytokinesis
Mitosis 
Sorting and division of genetic material; has 4 phases
Cellular reproduction: process of making new cell; also called cell division
Asexual reproduction: cells make identical copies of themselves without involvement of another cell
Most cells (including animal cells, plant cells & bacteria) able to reproduce asexually
Mechanism by which asexual reproduction occurs depends on type of cell; two main types
Eukaryotes: have nucleus and organelles; example: human cells
Eukaryotic cells much more complicated
Have to duplicate 46 chromosomes
Make sure that each cell gets all chromosomes and all the right organelles
Prokaryotes: do not have nucleus or organelles; example: bacteria
Prokaryotic cell division is simpler; cell need only: copy its DNA, divide up cytoplasm, and split in half; process called binary fission
Most of the time the cell cycle is in interphase where it is NOT dividing and is performing its normal function
This process of sorting chromosomes is called mitosis; only way eukaryotic cells can reproduce asexually
Take bacteria--- they simply copy their DNA, divide the cytoplasm, and split in half
One cell divides into two cells
Cytokinesis: division of cytoplasm 
The cell cycle is tightly controlled to avoid overproduction of cells (which can sometimes lead to cancer)
To avoid this, the cell has check points
Several places in cell cycle are checkpoints where cells must wait for signal to tell them to keep dividing
If something is wrong with cell or there is some reason cell should not reproduce, cell will not get signal and will stop dividing
If timing is good, cell will get go ahead signal and divide without interruption
Prophase 
Metaphase 
Anaphase 
Telophase 
Nucleus disappears, chromosomes become visible, set of chromosomal anchor lines or guide wires, spindle, forms
Chromosomes line up in center of cells
Chromosomes split and spindles pull them apart
Chromosomes go to far ends of cell, spindle disappears, and nuclei reappear
During or directly after telophase, cytokinesis happens and cell divides in half
Original cell was mother cell that has now formed into two new identical daughter cells
Thus mitosis (asexual reproduction), results in two new daughter cells identical to original mother cell
Purpose of mitosis
Provides the “new” cells fo body growth in the youth and is necessary to repair body tissues all through life. For example
Growth; example: bone (lengthening)
Muscles (increase in size with exercise)
Tissue replacement; example: red blood cells
Say you cut your hand, the skin is replaced, first by collagen, but then the skin is replaced
Meiosis 
Meiosis: sexual reproduction in which two different cells unite to form new cell
Used to make sperm and egg cells for sexual reproduction
Each parent cell produces four new cells that are not identical to parent cell and has only half normal number of chromosomes; other half of chromosomes contributed when sperm fuses with egg in sexual reproduction
Cancer 
When body is healthy, cells grow in orderly fashion; control system prevents cells from reproducing too fast
Sometimes conditions are altered that trigger changes in way cells reproduce; this wild, uncontrolled reproduction can lead to too many cells being produced, creating a lump, or tumor/neoplasm (new growth)
Not all tumors or neoplasms are cancerous
Tumors can generally be either benign or malignant
Benign tumors- a local affair
Tend to be surrounded by a capsule
Slow growth
Tend to push healthy cells out of the way. If they are removed before they compress vital organs they will seldom kill their host (person)
Generally non-life threatening
Malignant tumors -(bad neoplasms)
Rapid growth
Noncapsulated
Cells tend to be immature cells that tend to invade healthy tissues (like a crab- spread out into healthy tissue like the legs and pincers of a crab)
Can enter blood or lymphatic system and start new tumors in other parts of body; this kind of spread called metastasis
Reason lung cancer so deadly (more woman die from lung then breast) It metastasize for a long time before lung cancer is dx and it spread to the liver, and brain.
Cancer cells consume an exceptional amount of the body’s nutrients, leading to weight loss, and tissue wasting that contributes or gives way to death.
What causes this transformation in cells?
It is well known that radiation, mechanical trauma, viral infections, and many chemicals ( tobacco, tars, saccharine) can act as a carcinogen
All of these have one thing in common and that is the mutation that they cause.
Prognosis often determined by stage at diagnosis; two basic strategies for staging cancers
Staging based on amount of metastasis
Stage I: no cancer spread
Stage II: spread to nearby tissues
Stage III: spread to the lymphatic system
Stage IV: spread to distant organs
TNM classification of stages
Tumor characteristic or extent (T)
Number of lymph nodes invaded (N)
Any tumor metastasis (M)
Diagnosis of cancer
Imaging techniques (MRI, CAT, X-ray, etc.)
Blood tests
Biopsy (surgical examination of abnormal tissue)
Treatment of cancer; four main types; typically more than one type used to attack cancer
Chemotherapy: uses chemicals to kill rapidly dividing cells
Radiation therapy: uses energy to target cancer cells
Surgery: removes cancer cells from body
Biological or immunotherapy: trains body’s natural defenses to fight cancer cells
Typically, more than one treatment will be used
Success depends on stage at diagnosis and specific characteristics of the cancer itself
Microorganisms
Four primary microorganisms to be discussed, including:
Bacteria 
Viruses 
Fungi 
Protozoa 
* Your book describes them as microcitizens of a city.
Bacteria can be harmful, as in case of pathogens, or can be harmless and essential for life
FYI bacteria grows rapidly and reproduces by splitting in half, doubling as fast as every 30 minutes!
Harmless bacteria sometimes called normal flora
Certain bacteria in intestines help to digest food
Some help to synthesize vitamin K, needed for blood clotting
Infectious particles that have core containing genetic material surrounded by protective protein coat called a capsid
Cannot grow, eat, or reproduce by themselves; must enter another cell and use that cell for energy to grow and reproduce
Do not respond to antibiotics; can stay dormant in body and become active later in life
Plural form of fungus; can be one-celled or multi-celled organism; plant-like organisms with tiny filaments, called mycelia, that travel out from cell to find and then absorb nutrients
Good fungi, like edible mushrooms, are harmless; others can cause disease
Fungi spread through release of spores
Examples of fungal infections include athlete’s foot, thrush, or candidiasis
One-celled, animal-like organisms that can be found in water and soil
Diseases caused by these microorganisms can result from swallowing them or from being bitten by insects that carry them in their bodies
How microorganisms cause disease
Bacteria
Destroy body tissues
Destroy blood cells
Inhibit ribosomes
Cause fluid loss
Cause high fever
Cause decreased blood pressure
Increase blood clotting
Cause fluid in the lungs
Cause paralysis
Signs and symptoms of bacterial infection
High fever
Rapid pulse
Rapid breathing
Abnormal, often foul-smelling discharge from infected area
Pain at infection site
Swelling at infection site
Antibiotics used to treat bacterial infections
Chemicals kill prokaryotic bacteria without harming eukaryotic cells
Most antibiotics produced naturally by other microorganisms
click to edit
Virus
Viruses cause disease by
Causing cell to rupture and release viruses
Making good environment for secondary bacterial infection
Example: influenza can result in secondary bacterial pneumonia
Signs and symptoms of viral infection
Low grade fever (although sometimes can be high)
Muscle aches
General fatigue
Some have no symptoms
Some may be latent (hidden without symptoms) for many years, only to activate and cause symptoms later
Some may become chronic, causing low level symptoms for weeks, months, or even years
Shutting down cell
Few treatments for viral infections
Antibiotics do not kill viruses
Treatment for most is rest, fluids, and treatment of symptoms to keep patient comfortable
Some antiviral drugs, but because viruses use host cell’s machinery, drugs commonly affect host cell as well, causing side effects
Protozoa
Fungi
Fungal infections
Spores: tiny bodies resistant to environmental changes (able to stay dormant until conditions are just right)
Spores enter body through open wounds
Spores are inhaled
Most fungal spores do not cause disease in otherwise healthy individuals; exception is fungal infections of skin (such as athlete’s foot and jock itch
Many fungal infections opportunistic (only infect people with compromised immune systems or other underlying disease)
Symptoms of fungal infection vary depending on location of infection
Treatment of fungal infections is difficult
Most anti-fungal drugs are highly toxic
Many fungal infections are resistant to treatment
Symptoms vary depending on type of protozoan
Many are serious disease causing long term debilitating illness; example: malaria, which is transmitted by mosquitoes
Some are relatively mild illnesses; example: “beaver fever” caused by Giardia, protozoan that lives in streams and water supplies contaminated by fecal matt