Chapter 3: Cell Structures

3.2: Cell Features and Cell Organelles

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The Cell Theory• 1938: Mattias Schleiden concluded cells made up every part

of a plant• 1939: Theodor Schwann claimed that animals were also made

of cells• 1958: Rudolph Virchow determined that cells come only from

other cells• These three observations form the CELL THEORY, which states:

1. All living things are made of one or more cells.2. Cells are the basic units of structure and

function in organisms.3. All cells arise from existing cells.

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Cell Size• Small cells function more efficiently than large cells. • This is because they have a high surface area to volume ratio. • We have lots of small cells so that all the substances that

leave and enter cells have a large surface area to do it. If the surface area-to-volume ratio is too low, substances do not have enough space to move across.

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Common Cell Features• Cells share common structural features,

including:

– Cell membrane

– Cytoplasm

– Cytoskeleton

– Ribosomeshttp://visual.merriam-webster.com/animal-kingdom/simple-

organisms-echinoderms/animal-cell.phpBuck Salinas 2012

Common Cell Features• Cell Membrane: outer boundary of the cell,

regulates what enters and leaves a cell• Cytoplasm: the cell interior, which contains many

structures• Cytoskeleton: a system of microscopic fibers that

suspend structures inside the cell• Ribosomes: cellular structures on which proteins

are made• Additionally, all cells contain DNA (unless they lose

their DNA later).

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Prokaryotic Cells• Prokaryote: the smallest and

simplest cells, single-celled organisms that lack a nucleus and other internal compartments (organelles).– Because they have no organelles,

they cannot carry out many specialized functions.

• The familiar prokaryotes that cause infection belong to a type of prokaryotes called bacteria.

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Characteristics of Prokaryotes• Exist in a broad range of environmental conditions.• A prokaryote’s enzymes and ribosomes are free to move

around in the cytoplasm because there are no internal compartments (organelles).

• Prokaryotes have a cell wall surrounding the membrane for structure and support.– Prokaryotes lack a strong internal support system.– Prokaryotes have a cell wall made of polysaccharides

connected to amino acids.– Some cell walls are surrounded by a capsule which allows

prokaryotes to stick to things!• Many prokaryotes also have flagella—long, threadlike

structures for movement. Buck Salinas 2012

Eukaryotic Cells• Eukaryotes: an organism with a cell nucleus

– Some eukaryote cells use flagella, others have hairlike cilia for movement.• Nucleus: an internal compartment that houses the cell’s DNA.• Organelles: an internal compartment that carries out specific

activities in the cell.– A complex system of internal membranes connects some organelles inside

the cytoplasm.

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The Cytoskeleton• Provides the interior

framework of an animal cell.• Composed of protein fiber

network anchored to plasma membrane.

• Three types of fibers:1. Actin fibers: long slender

microfilaments, shape the cell2. Microtubules: hollow tubes,

the highway system for transport of information

3. Intermediate fibers: provide a frame for ribosomes and enzymes Buck Salinas 2012

09/14/12 DOL

• 1-4. On the provided whiteboard, draw a basic cell and label 4 parts found in ALL cells.• 5. Next, draw something special that

is only found in Eukaryotic cells that contains DNA and label this part. Circle the label.

The Cell Membrane• The inside of the cell (cytoplasm) is contained by

the cell membrane.• The cell membrane is fluid and selectively

permeable, allowing only certain substances in the environment to pass through.

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The Cell Membrane as a Barrier• The selective permeability of the membrane is caused by the way

phospholipids interact with water.– A phospholipid has a polar “head” and two nonpolar “tails”

• Lipid Bilayer: the arrangement of phospholipids in the cell membrane. Nonpolar tails make up the interior of the bilayer because water in and out of the cell repels the nonpolar tails.– Ions and most polar molecules are repelled. Lipids are allowed to pass

through.Buck Salinas 2012

Photos: http://www.bioteach.ubc.ca/Bio-industry/Inex/

Membrane Proteins• Various proteins are located in the lipid bilayer.• Proteins are made of amino acids. Some amino acids are polar, others are

nonpolar. – The nonpolar part of a membrane protein is attracted to the interior of the lipid

bilayer but repelled by the water on either side. This holds the protein in place.• Membranes contain different proteins.

– Marker Proteins: attached to a carbohydrate advertise cell type.– Receptor Proteins: bind signal molecules outside the cell. – Enzymes: involved in biochemical reactions in the cell.– Transport: aid in the movement of substances into and out of the cell.

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09/20/12 DOL #1

• On your whiteboard, draw a phospholipid. • Label the parts and indicate if each

part is polar or non polar.• Finally, draw a small section of the

lipid bilayer that demonstrates how the phospholipids are oriented.

Cell Structure

Ch. 3.3

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The Nucleus • Controls most functions of the cell.• Surrounded by a double membrane known as the nuclear

envelope, made of two lipid bilayers.• Nuclear pores, small channels, are scattered over the surface of

the nuclear envelope so substances made in the nucleus can move into the cytoplasm.

• The hereditary information of a cell is coded in the DNA, which is stored in the nucleus.

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Ribosomes and the Endoplasmic Reticulum • Eukaryotic cells have a system of internal membranes

that play a role in the processing of proteins. • Cells make proteins on ribosomes. Each ribosomes is

made of proteins and RNA. Some ribosomes are found “free” in the cytoplasm (cytosol) while others are on the surface of the endoplasmic reticulum.

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Production of Proteins• Proteins that are exported from the cell are made on ribosomes on the

surface of the endoplasmic reticulum.– Endoplasmic Reticulum: a system of internal membranes that move proteins

and other substances through the cell. Made of a lipid bilayer.• The ER with ribosomes is called rough ER.

– The rough ER helps transport the proteins made by the ribosomes.– Each protein crosses the membrane and enters the ER. The portion of the ER

with the protein pinches off to form a vesicle.• Vesicle: a small, membrane-bound sac that transports substances in cells.

• The rest of the ER with no ribosomes is the smooth ER.– Makes lipids and breaks down toxic substances.

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Packaging and Distribution of Proteins• Vesicles that contain newly made proteins move through the cytoplasm

from the ER into an organelle called the Golgi Apparatus. Enzymes in the Golgi modify the proteins and enclose them in new vesicles.– Golgi Apparatus: a set of flattened, membrane-bound sacs that

serve as the packaging and distribution center of the cell.• Lysosomes: other vesicles which are small, spherical organelles that

contain the cell’s digestive enzymes. The ER, Golgi, and Lysosomes work

together in protein production,

packaging, and distribution.

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Mitochondria• Mitochondria: an organelle that harvests energy from organic

compounds (biomolecules) such as sugar such as to make ATP. • Cells like muscle cells that use a lot of energy can have thousands of

mitochondria.• The outer membrane is smooth, the inner membrane is folded. These

membranes are where the chemical reactions take place.• Mitochondrial DNA: independent of nuclear DNA, similar to bacterial

DNA

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Plant Cells• Plant cells have there additional

structures not found in animal cells.

1. Cell Wall: a thick wall of proteins and carbohydrates including cellulose. Supports and maintains cell shape.

2. Chloroplasts: Organelles that use light energy to make sugar. Have DNA like mitochondria.

3. Central Vacuole: a large membrane-bound space that stores water and helps to make the cell rigid so plants can stand upright. Buck Salinas 2012

09/20/12 DOL #2

• On the whiteboards, draw FOUR organelles we learned about today. Next to each organelle, BRIEFLY describe the function (what it does!) of the organelle!

Journal Entry

• Write down three new things you learned about bacteria.• Are bacteria as bad as you thought?

Explain.• At the end of 5 minutes, I want to

see at least FIVE written sentences!

Bacteria

Ch. 20.2

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Bacteria: A ProkaryoteBacteria (Prokaryotes)Differ from Eukaryotes in at least seven ways:1. Internal Compartmentalization—bacteria don’t have them,

while eukaryotes do. 2. Cell Size—prokaryotes like bacteria are smaller than eukaryotes. 3. Multicellularity—prokaryotes like bacteria are never

multicellular, eukaryotes can have multiple cells.4. Chromosomes—prokaryotes have one circular chromosome,

eukaryotes have linear chromosomes. 5. Reproduction—prokaryotes only reproduce asexually, through

binary fission while eukaryotic reproduction varies by species. 6. Flagella—prokaryotic flagella are less complex than eukaryotic

flagella. 7. Metabolic Diversity—bacteria have many metabolic abilities

that eukaryotes do not have. Buck Salinas 2012

Bacterial Cell Shapes• Bacterial cells are usually one of three basic shapes.

– Bacillus: rod-shaped cells– Coccus: round-shaped cells– Spirillium: sprial-shaped cell

• Species that form filaments (strings) are indicated by the prefix strepto- while those that form clusters are indicated by the prefix staphylo.

• Members of the kingdom Eubacteria have a cell wall made of peptidoglycan (polysaccharides and amino acid chains).

• Outside the cell wall and membrane, many bacteria have a capsule. – Capsule: a gel-like layer, allows bacteria to stick to things

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Bacterial Cell Shapes• Cell Walls: Eubacteria have two types of cell walls, distinguished

by a dye called Gram stain (Gram negative, Gram positive). This is important because it helps determine the type of antibiotics needed to fight the bacteria.

• Endospores: Some bacteria form thick-walled endospores around their chromosomes with a bit of cytoplasm when the bacteria are exposed to harsh conditions. This allows the bacteria to remain dormant and survive the environmental stress.

• Pili: Allow bacteria to adhere to the surface of sources of nutrition. Also allow bacteria to connect and exchange genetic material.– Conjugation: a process in which two organisms exchange genetic

material. In prokaryotes, pili from on bacterium connects to a second and genetic material is exchanged.

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Obtaining EnergyBacteria can live in many conditions and obtain

nutrients and energy in many ways.• Photosynthesizers: use light to make energy.

– Carry out much of the photosynthesis in the world, often found in aquatic locations

• Chemoautotrophs: obtain energy by removing electrons from inorganic molecules such as ammonia and hydrogen sulfide– Often live in the soil and are important to the

environment and agriculture because they complete Nitrification for plants.

• Heterotrophs: break down the bodies of dead organisms and make nutrients available to other organisms – Decomposers, break down dead material, can

secrete poison into food, fix nitrogen. Buck Salinas 2012

Escherichia coli

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Pathogenic Bacteria• Your body is full of resources such as minerals, fats, carbs, and

vitamins. Bacteria have evolved means of obtaining these resources, and this can make us ill.

• Heterotrophic bacteria obtain their nutrients by secreting enzymes that can metabolize their environment. If that environment is your body, it can cause problems!

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Bacterial Toxins and Biowarfare

• Bacterial Toxins: bacteria can also cause disease by secreting chemical compounds into the environment.– When bacteria grow in food and

produce toxins, the toxins can make us sick.

– Clostridium botulimun– Escheria coli O157:H7

• Biowarfare: the deliberate exposure of people to biological toxins or pathogens such as bacteria or viruses.

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Antibiotics• In 1928, Alexander Fleming noticed a

fungus in Penicillium genus growing on a bacterial culture. No bacteria grew near the fungus.

• Scientists found that this fungus was useful at fighting bacterial infections.

• Recently, some bacterial have become resistant to antibiotics.– Antibiotic Misuse: many people do not take

the full course of antibiotics—they end their treatment too early allowing resistant bacteria to survive and reproduce.

– Multiple-antibiotic Resistance: some bacteria have because resistant to several different antibiotics. Buck Salinas 2012

Importance of Bacteria• Probiotics: used to promote bacterial growth in the

human digestive tract. Foods such as yogurt contain active cultures of bacteria and provide a source of bacteria for the human digestive tract.

• Food and Chemical Production:– Many of the foods that we eat are processed by bacteria.

• Pickles, buttermilk, cheese, sauerkraut, olives, vinegar, sourdough bread

– Humans are also able to use bacteria for industrial uses including making acetone.

– Genetic engineering allows bacteria to produce compounds.

• Mining and Environmental Uses of Bacteria: – Mining companies can use bacteria to concentrate

elements from ore.– Bacteria metabolize different compounds and are used to

clean up oil and chemical spills. Buck Salinas 2012

09/24/12 DOL• On the Venn Diagram side of your dry

erase board, compare and contrast prokaryotes and eukaryotes.• At the end of 5 minutes, I want to see

AT LEAST 3 points under prokaryotes, eukaryotes, and both!–More is even better!!!

Introduction to Microscopes

• Today we will be using a light microscope, where light passes through one or more lenses to produce an enlarged image of a specimen.

Photo: http://www.chemistryland.com/CHM130S/07-Mole/Mole.htm

Cells and Their Environments

Chapter 4.1: Passive Transport

Passive Transport

Movement across the cell membrane that does not require energy!

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Diffusion• Your body responds constantly to

external conditions to maintain a stable internal environment.• Homeostasis: the maintenance of

constant internal conditions in spite of changing external conditions. –Homeostasis can be conducted in many

ways including moving substances across the cell membrane with or without energy from the cell. Buck Salinas 2012

Random Motion and Concentration• Passive Transport: Movement across the cell membrane that

does not require energy.• Concentration Gradient: a difference in the concentration of a

substance across a space• Equilibrium: a condition in which the concentration of a

substance is equal through

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Movement of Substances• Particles of substances of a solution move around randomly.• Concentration gradients cause substances to move from an

area of high concentration to an area of low concentration.• Diffusion: the movement of a substances from an area of high

concentration to an area of lower concentration caused by the random motion of particles

• The cell membrane is selectively permeable to substances; the nonpolar interior of the lipid bilayer repels ions and most polar molecules.– Many substances such as molecules and ions enter or leave the cells

by diffusing across the membrane. – Concentrations are different inside the cell than they are outside, so

substances move “down” the concentration gradient (high to low!).• Diffusion Video

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Osmosis• Osmosis: the diffusion of water through

a selectively permeable membrane• Because water molecules are so small,

they can diffuse through the membrane even though they are polar. – Osmosis is caused because some water

molecules are attracted to ions on one side or the other of the membrane. If the different sides of the cell have different concentrations of dissolved particles, they will have different concentrations of “free” water. Osmosis occurs as free water moves into the solution with the lower concentration of free water.

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Hypertonic, Hypotonic, Isotonic• Three directions water can move in a cell:

1. Water moves out: hypertonic solutions cause a cell to shrink; the solution outside has a higher concentration of dissolved particles than cytosol (cytoplasm).

2. Water moves in: hypotonic solutions cause a cell to swell; the solution outside has a lower concentration of dissolved particles than cytosol (cytoplasm). Could cause a cell to burst.

3. No net water movement: isotonic solutions cause no change in cell volumes; the cytosol (cytoplasm) and outside solution have the same concentration of free water molecules.

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Crossing the Cell Membrane• Osmosis Video

• Most ions and polar molecules cannot pass across the cell membrane because they cannot pass through the nonpolar interior of the lipid bilayer.

• However, polar substances can cross using transport proteins.– Transport Proteins: provide polar passageways through which

ions and polar molecules can cross the cell membrane

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Diffusion Through Ion Channels• Ions (Na+, K+, Ca2+, Cl-) are needed in cells but cannot diffuse

across the cell membrane.• Ion Channel: a transport protein with a polar pore through

which ions can pass.• The pores of some ions are always open. Other ion channels

must be opened or closed based upon external stimuli.

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Electrical Charge and Ion Transport• The rate of movement of a substance across the cell

membrane is generally determined by the concentration gradient of the substance.

• The movement of a charged particle, such as an ion, across the cell membrane is also influenced by the particle’s positive or negative electrical charge.

• The direction of movement caused by an ion’s concentration gradient may oppose the direction of movement caused by the ion’s electrical charge, often affecting the diffusion of ions across the cell membrane.

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Facilitated Diffusion• Most cells have a transport protein that can bind to a specific substance

on one side of the cell membrane, carry the substance across the membrane, and release it on the other side. These are carrier proteins.

• When carrier proteins transport substances down the concentration gradient, the transport is facilitated diffusion.

• Facilitated Diffusion: a type of passive transport that moves substances down their concentration gradient WITHOUT using the cell’s energy

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Active Transport

The transport of a substance across the cell membrane against its concentration gradient requiring energy from the cell.

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Cells and Their EnvironmentsChapter 4.2: Active Transport

Movement Against a Concentration Gradient

• Facilitated diffusion can only transport substances down their concentration gradient.

• Active Transport: the transport of a substance across the cell membrane against its concentration gradient– Active transport requires the cell to use energy because

the substance is being moved against its concentration gradient.

– Usually this energy comes from ATP.– Some active-transport processes involve carrier proteins

which require energy and act as pumps to move substances against their concentration gradient.

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Sodium-Potassium Pump• Extremely important in animal cells.• In a complete cycle, it transports three sodium ions (Na+) and two potassium

ions (K+) into the cell because sodium cells are usually more concentrated outside the cell than inside, while potassium are usually more concentrated inside the cell.– The energy for this pump is provided by ATP.– This prevents sodium from accumulating in the cell (what would happen if there were too

many).– Helps maintain the concentration gradient because this is used to transport other

substances.

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Movement in Vesicles• Some substances (proteins, polysaccharides) are too large to

be transported by carrier proteins and instead use vesicles.– Vesicle: a small cavity or sac in a eukaryotic cell made of cell

membrane; part of the membrane surrounds the materials to be taken into the cell.

– Endocytosis: the movement of a substance into a cell by a vesicle.– Exocytosis:the movement of a substance by a vesicle to the outside

of the cell.

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Membrane Receptor Proteins• Cells respond to important information and filter out unimportant

information using specialized proteins that bind to signal molecules.– Receptor Proteins: proteins that bind to a specific signal molecule,

enabling the cell to respond to the signal molecule.– Example: the muscles of a person exercising could not contract without

receptor proteins and signal molecules that tell muscles when to contract and relax.

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Ch. 42 Hormones and the Endocrine SystemCh. 39.3 Excretion

Relating transport in cells to human body systems

Photo: http://www.chemistryland.com/CHM130S/07-Mole/Mole.htm Buck Salinas 2012

The Function of Hormones• Hormones: substances secreted (released) by cells that

act to regulate the activity of other cells in the body.– Hormones act like chemical messengers, carrying

instructions all over your body. • Hormone Functions:– Regulating growth, development, behavior, and

reproduction.– Coordinating the production, use, and storage of energy. – Maintaining homeostasis (temperature regulation,

metabolism, excretion, and water and salt balance). – Responding to stimuli from outside the body.

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The Endocrine System• Hormones are produced

by a system called the ENDOCRINE SYSTEM!

• Endocrine Glands: ductless organs that secrete hormones directly into either the bloodstream or the fluid around cells (extracellular fluid).

• All endocrine glands and hormones together make up the Endocrine System.

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How Hormones Act on Target Cells• Target Cell: a specific cell that a hormone binds to

and acts on (carries the message to it) after leaving the cell in which the hormone was made.

• A hormone recognizes a target cell because the target cell has specific receptors.

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Amino-Acid-Based Hormones• Amino-Acid-Based Hormones: hormones made of

amino acids. These hormones are usually water soluble.

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Steroid Hormones• Steroid Hormones: lipid (not soluble in water)

hormones that the body makes from cholesterol. Steroid hormones are fat soluble.

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Feedback Mechanisms• The human body makes more than 40 hormones,

and it must regulate the release. • The endocrine system plays an important role in

homeostasis: different hormones moving through the bloodstream affect specific target tissues, and the amounts of various hormones must be maintained in a very narrow range.

• Feedback mechanisms detect the amount of hormones in circulation and the endocrine system then adjusts the amount of hormones being made or released.

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Positive Feedback• Positive Feedback: when high levels

of a hormone stimulate the output of even MORE hormone.–Example: the hormone that stimulates

egg release also regulates the female hormone estrogen. A rise in estrogen levels, however, will stimulate the release of more of the regulatory hormone.

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Negative Feedback• Negative Feedback: a change in one direction stimulates the control

mechanism to counteract further change in the same direction. – Controls most hormone release in humans.– Example: high levels of a hormone inhibit the production of more hormone,

whereas low levels of a hormone stimulate the production of more hormone. – The liver plays a role in negative feedback by removing the hormones from the

blood and breaking them down. – Negative feedback works like trying to maintain a certain speed by pressing or

releasing the gas pedal.

In negative feedback, a secondary substance

blocks production of its initial stimulating

substance. Buck Salinas 2012

Endocrine Control: Endocrine system and the Nervous System

• Feedback mechanisms fine-tune the level of hormones in circulation, but two endocrine glands control the initial release of many hormones. – Hypothalamus: area of the brain that coordinates the

activities of the nervous and endocrine systems.– Pituitary Gland: an endocrine gland by the hypothalamus

that secretes many hormones, including some that control other endocrine glands.

• The endocrine system and nervous system interact to coordinate the body’s activities. Both the endocrine and nervous system send chemical messengers.

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Feedback: Insulin and Glucagon

http://health.howstuffworks.com/diseases-conditions/diabetes/

diabetes1.htm

• Two hormones made by the islets of Langerhans in the pancreas control glucose levels in the blood.• Insulin: a hormone that lowers

blood glucose levels by promoting the accumulation of glycogen in the liver.

• Glucagon: raises blood glucose levels by releasing glucose that was stored as glycogen.

• Diabetes mellitus: disorder in which cells are unable to obtain glucose from the blood, resulting in high blood glucose levels.• Type I: hereditary autoimmune disease, usually

develops before age 20.• Type II: often develops in people over age 40 due to

obesity and inactivity. Buck Salinas 2012

Homeostasis and the Endocrine System

• Changes in external conditions, such as increased temperature, cause homeostatic responses to the effects of the internal changes.

• Both the endocrine system and the nervous system are very important to homeostasis.– Feedback mechanisms may inform nervous system

components to stimulate hormone release by endocrine glands.

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Water and Metabolic Wastes• Cleaning up must be done to maintain a healthy living

environment. • The body must remove wastes and maintain osmotic

balance and stable pH by either excreting or conserving salts and water.

• Excretion: the process that rids the body of toxic chemicals, excess water, salts, and carbon dioxide while maintaining osmotic and pH balance. – Excess water is excreted through the skin in sweat and through

the kidneys in urine.– In the liver, ammonia is converted to the much less toxic urea

and carried to the kidneys where it is removed from the blood.Buck Salinas 2012

The Kidneys: Blood Filters

• Kidneys regulate the amount of water and salts in the blood.

• Nephrons: tiny blood-filtering tubes in the kidneys.– The functional unit of the

kidney!• Three phases in the kidneys:

– Filtration: begins at the cup-shaped capsule called the Bowman’s capsule.

– Reabsorption and Secretion: filtrate passes into renal tubes

– Urine Formation: urine is secreted formed from water, urea, and salts

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Elimination of Urine• Kidneys: organs that filter

blood and regulate the amount of water and salts (maintaining homeostasis!!!)

• Ureters: move urine from the kidneys to the urinary bladder.

• Urinary Bladder: a hollow, muscular sac that stores urine and expands gradually as it fills.

• Urethra: the tube through which urine leaves the bladder and exits the body.

Buck Salinas 2012

10/02/12 DOL

• On your white board:1. Relate the endocrine system to

homeostasis.2. Relate the excretory system to

homeostasis.3. Relate the endocrine system to

diffusion.4. Relate the excretory system to diffusion.