Download HOMEOSTASIS: Maintaining Living Systems Homeostasis

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HOMEOSTASIS: Maintaining Living Systems
Homeostasis: maintaining a relatively constant, stable internal environment
• human body examples:
• blood pH =7.4
body temp. = 37°C
• blood pressure = 120/80
blood [glucose] = 0.1%
Homeostatic Mechanisms: all the body systems help to maintain homeostasis.
• Respiratory system: [gases] in blood
° take in O2 (used up) & remove CO2 (produced)
• liver and kidney's: monitor and maintain constant blood chemistry
Control of Homeostasis
STIMULUS
RECEPTOR
Negative Feedback
REGULATOR
CENTER
Normalcy
ADAPTIVE
RESPONSE
NEGATIVE FEEDBACK MECHANISM
Receptors (sensors)
• detect unacceptable levels (e.g. if skin gets colder than 37°C temperature
sensors detect change).
• found all over body
• sends signal to appropriate brain center
Regulator Center
• Brain control centers (e.g. in the hypothalamus) monitor and control body conditions
(e.g. pH, temperature, glucose levels)
Adaptive Response
• An alternate behavior (e.g. shivering)
• Directed by regulator center
Normalcy
• normal state is regained
• Once normalcy is attained, sensor stops signaling the regulator center (negative
feedback), so adaptive behaviour stops
• results in a FLUCTUATION between two levels.
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Positive feedback mechanisms exist but we will study these later
BIOCHEMISTRY & CELL COMPOUNDS
Biochemistry: the chemicals of life and their study
Organic Chemistry: the study of carbon compounds
Why Carbon?
1.
has four available covalent bonds -- allows for other atoms to bind.
2.
forms strong bonds with itself
• forms long chains - straight or branched many combinations
• Carbon single bonds rotate
• Can form single, double, and multiple ring structures (e.g. glucose,
nucleotides)
C
WATER - Structure, Properties and Importance
Water is...
• inorganic (contains no carbon)
•
covalently bonded, but is POLAR
•
held together by hydrogen bonds
δ-
O
H
δ+
H
δ+
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POLAR – when electrons are not shared equally in a covalently bonded molecule
• O has a slight net negative charge
• H have a small net positive charge
Hydrogen Bonds occur when H bonds with O, F or N
• H bonds dotted line
•
Covalent and ionic bonds much stronger than H bonds
•
Numerous H bonds add up large effect explains some of the unique properties
of water.
δ+
H
δ-
H
δ-
O
O
H
δ+
H
δ+
O
δ-
δ+
H
δ+
H
δ+
Water is Essential to All Life
•
Life began in water
•
all living organisms are “water-based.”
•
living organisms have adaptations for maintaining water levels (e.g. human skin,
plant stomata)
Humans life requires water:
i.
we are ≈ 70% water.
ii.
only dissolved substances can enter cell membrane of our cells (e.g. glucose,
amino acids).
iii.
water carries away dissolved cellular wastes and excreted wastes (sweat,
urine)
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can dissolve ions necessary for body processes (e.g. Ca++ for movement, Na+,
iv.
K+ nerve impulses)
v.
joints lubricated by a watery fluid
vi.
brains partially protected against shock by a watery layer
vii.
sense organs require water: eyes filled with thick fluid; hearing depends upon
fluid-filled structure (Cochlea) that transmits vibrations.
WATER HAS SEVERAL UNIQUE CHARACTERISTICS
•
abundant throughout biosphere
•
H-bonding causes a low freezing point and a high boiling point liquid at body
temperature.
•
H20(l) H20(g) absorbs much heat before it warms up or boils
•
H20(s)  H20(l) gives off much heat before it freezes
•
°
maintains ocean’s constant temperature
°
accounts for cooling effect of sweating
high COHESIVENESS (sticks to other materials and itself) good for transporting
materials through tubes.
•
Density? H20(s) < H20(l)
°
•
ice will form on top Ice protect organisms below.
dissolves other polar molecules good solvent in lab and our bodies
°
promotes chem. Reactions
°
Called the “UNIVERSAL SOLVENT.”
ALL DUE TO
HYDROGEN BONDING
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ACIDS, BASES, & BUFFERS
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ACIDS: compounds that dissociate in water and release H+ ions. (e.g. HCl, H2CO3, H2O)
•
BASES:
•
pH: measures concentration of H+ ions
°
°
°
°
•
compounds that dissociate in water and OH- ions. (e.g. NaOH, KOH, H2O)
range 0 to14.
pH ↓than 7.0 is acidic.
pH ↑ than 7.0 is basic
pH of 7 is neutral (pure water)
pH formula:
pH = -log[H+]
-3
if [H+] = 10 ... pH=-log[10-3] = 3
•
pH scale is a logarithmic scale
°
°
°
each number on the pH scale = a difference in magnitude of 10.
pH of 2 is 10 x more acidic than a pH of 3.
pH of 2 is 100 x more acidic than a pH of 4.
How does the basicity of ph 10 compare to pH 4?
10
-
4
=
6
°
°
°
tears ____
human blood ____
oven cleaner ____
pH of 10 is 1,000,000 x more basic than a pH of 4.
What is the pH of the following (p.29)?
° stomach acid ____
° beer ____
° urine ____
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Why is pH important? (remember homeostasis)
° living things need a constant pH
° ∆ pH enzymes denature lose function
°
livings cells use buffers keep pH constant.
•
°
°
BUFFER: chemical that take up excess H+ ions or excess OH- ions.
Buffers resist changes in pH when acid or base is added.
buffers can be overwhelmed too much acid or base added.
•
SALT: formed in a neutralization reaction between an acid and a base. e.g. HCl + NaOH ⇒
H2O + NaCl (table salt)