Physiology test 1

Homeostasis

ability of an organism to maintain a consistent internal environment regardless of external conditions

receptor

detects change

control center

determines what change should be made (negative / positive feedback)

effector(typically muscles and glands)

the change that occurs (back to homeostasis)

Intrinsic control

begins within an organ

-Ex. Heart cells initiate contraction of heart cells and set the rate the heart contracts

Extrinsic control

begins outside of an organ

-Ex. ANS can change the rate and force the heart beats

ANABOLIC METABOLISM

Building larger molecules from smaller molecules

• Example: building new muscle tissue (proteins) from the amino acids in your food

• These reactions require energy, known also as an endergonic process

CATABOLIC METABOLISM

Breaking large molecules into smaller ones

• Example: Digesting the nutrients in your food to release the energy stored in them

• These reactions release energy (exergonic process) for the body to use.

Regulation

Adjust the internal bodily functions to maintain homeostasis despite disruptive changes

Examples:

Rest → Exercise

Indoors (cool) → Outdoors (hot)

Reproduction

• Produce new cells for maintenance, growth and repair (mitosis)

• Produce eggs and sperm for reproduction of a new organism (meiosis)

Environmental factors

must be maintained to keep each cell healthy:

1. Concentration of

a) Nutrients

b) Oxygen and carbon dioxide

c) Waste products

d) Water and electrolytes

2. pH

3. Temperature

4. Volume and pressure of body fluids

Negative feedback

allows regulatory mechanisms to fine-tune homeostatic conditions through small adjustments = Most common control mechanism

opposite ↑↓

Positive feedback

amplifies the response = Uncommon control mechanism

continues ↑↑ or ↓↓

Element

• A substance that can not be broken down further and still maintain its characteristics 

• 26 normally found in the body 

• 96% of human composed of O,C,H,N, Smallest unit is called an atom

Atomic Structure

•The nucleus of an atom is made up of protons and neutrons.

Electrons

Particles that move rapidly around the nucleus.

Electrical Charge

•Electrons have a negative charge

•Protons have a positive charge

Chemical Bonding

•Energy relationships that hold atoms together

•When bonds are made, or broken energy is either required or released

•Types: ionic, covalent, hydrogen

Chemical Bonds and Energy

•Chemical bonds store energy

•When chemical bonds are broken, energy is released

Ionic bonds

formed between oppositely charged ions where one ion gives an electron and one ion receives an electron

When an atom loses or gains electrons

it becomes electrically charged

Charged atoms are called

ions

Covalent Bonds

• Two atoms share one or more pairs of outer-shell electrons.

• Usually stronger than ionic bonds

nonpolar

equal sharing

polar

unequal sharing

The number of covalent bonds an atom can form =

number of additional electrons needed to fill outer shell

single covalent bond

the sharing of one pair of valence electrons

double covalent bond

sharing of two pairs of valence electrons

Hydrogen Bonds

•Weakest bond that involves partially charged atoms, between molecules

•Easily seen between water molecules

Molecules

2 or more atoms bonded together O2, H2O, HCl

Compounds

2 or more different elements bonded together

Most compounds can also be…

molecules, except ionically bonded compounds HCl, H2O, NaCl

Polarity

•Unequal sharing of electrons between different types of atoms which are covalently bonded together.

-Allows water molecules to interact with one another and with other polar molecules (hydrophilic)

non-polar molecules are…

hydrophobic

Surface tension

water molecules stick to one another (hydrogen bonds)

High boiling point

lots of heat is needed to break H bonds and keep them from reforming

Evaporative coolant

•to convert water from a liquid to a vapor, it takes a certain amount of heat called the heat of vaporization

•Used by skin and respiratory system

Water acts as a SOLVENT

lots of compounds can be dissolved in it

Tonicity

comparison of the solute concentrations of two solutions

Hypertonic

more concentrated (more solute)

Hypotonic

less concentrated (less solute)

Isotonic

solute concentrations are the same in both solutions

Cells placed in a hypotonic solution will…

swell, possibly until they burst (hemolysis)

Cells placed in a hypertonic solution will…

shrink (crenation)

Cells placed in an isotonic solution…

will not shrink or swell

Diffusion

the movement of molecules from an area of higher concentration to an area of lesser concentration until equilibrium is reached

Osmosis

the diffusion of water through a selectively permeable membrane

ACIDS

in a solution, they release hydrogen ions (H+) into the solution. The more H+ it releases the stronger it is

BASES

in a solution, they give off hydroxyl ions (OH-) into the solution

• NaOH (sodium hydroxide) becomes Na+ and OH- in a solution.

• can bind to hydrogen ions

Average blood pH

7.4

Acidosis

blood pH falls below 7.35

Alkalosis

blood pH is above 7.45

Death occurs if blood pH goes outside the range of…

6.8-8.0 for more than a few seconds

Buffers

Chemicals which help to minimize pH changes when an acid or base is added to the body fluid

Macromolecules

Large organic molecules

Polymers

long chains of smaller repeating molecules (monomers)

lipids cell functions

• energy storage

• major component of the cell membrane

• chemical messengers

Monomer of lipids

Fatty acids

Saturated fats

every C is filled with H.

• Solid at room temperature

Unsaturated fats

some C form double bonds

• Liquid at room temperature

Examples of Lipids

a) Triglycerides- fats and oils

b) Phospholipids- found in cell membranes

Steroids

molecular structure containing four rings of carbon atoms (three six-membered and one five).

• Ex. Cholesterol - component of cell membrane

• Ex. Sex hormones

Eicosanoids

short distance messengers, mostly act on the cells that produce them or on neighboring cells, over short distances and time periods, and therefore can be classified as autocrine/paracrine hormones

Ex. Prostaglandins

carbohydrates cell functions

• Energy Storage

• Source of energy for all cellular functions

• Structural

Monomer of carbohydrates

simple sugars

glucose =

cellular fuel

Complex Carbohydrates

long chains of simple sugars (polysaccharides)

examples:

• starch (plant energy storage)

• cellulose (plant structure)

• glycogen (animal energy storage)

Nucleic acids and nucleotides cell functions

a) genetic info

• DNA (chromosomes or chromatin)

• RNA (protein synthesis)

b) energy transport

• ATP (high-energy nucleotide)

Monomers of Nucleic Acids

Nucleotides

polymers of nucleic acids

DNA & RNA

What is ATP?

Adenosine Triphosphate

• Contains one nucleotide

proteins cell functions

• Structural (cell parts, hair, muscle)

• Regulatory (hormones)

• Transport (hemoglobin)

• Antibodies (disease prevention)

• Enzymes (speed up chemical reactions)

Monomer of Proteins

Amino Acids

Primary structure of proteins

a simple chain of amino acids

Extreme conditions can change the structure of a protein

• Extreme heat or very high or low pH can cause a protein to become denatured (a change in 3-dimensional structure)

What are enzymes?

• Catalyze chemical reactions

• Are made up of protein

• Have an active site where a substrate can fit (like a key in a lock)

Are sensitive to changes in temperature and pH

A cooler temperature will…

slow down an enzyme reaction

A warmer temperature will…

speed up an enzyme reaction

Extreme heat will…

denature an enzyme

If the pH is more acidic than the optimum, the reaction will…

slow down

If the pH is more basic than the optimum, the reaction will…

slow down

Extreme acid or base will…

denature an enzyme

Exchange reactions

exchanges between molecules (very common in the human body)

Example: in muscle, creatine phosphate → ATP

Catabolic (decomposition) reactions

breaking molecules down into smaller pieces

– Digestion of nutrients

Anabolic (synthesis) reactions

building molecules

Ex. making new proteins for muscle growth

Enzymes

Increases rate of reaction by decreasing the activation energy needed to start a reaction

(biological catalyst, most are proteins)

Enzyme rules

• Can’t make anything happen that wouldn’t normally occur

• Not permanently altered, recycled

• Work in forward or reverse direction

• Ex. Sucrose fructose + glucose

• Specific to substrate

• Ex. Sucrase, maltase, lactase

Mechanisms

• Help substrates get together

• Orientating substrates in positions that favor reactions (active sites); forming enzymes-substrate complex

• Inducing a fit (induced fit model) between enzymes and substrate sometimes called a key-lock system

• Shutting out water molecules

Regulation of Enzyme Activity

• pH, temperature, salt concentration all affect enzyme function. Denaturation

• Enzyme saturation: substrate concentration

• Competitive vs noncompetitive inhibition

four overall steps of cellular respiration

(I) Glycolysis

(2) Intermediate stage

(3) Citric acid cycle

(4) Electron transport system

Cellular Respiration

• The process of breaking down glucose in many steps – releasing energy

• Aerobic Respiration: used by most cells to produce large amounts of ATP

• Oxygen is required

• C6H12O6 + 6O2 + 6H2O → 6CO2 + 12H2O + E

• Stages: Glycolysis, Krebs cycle & Electron transport

Glycolysis

• Takes place in the cytoplasm; doesn’t require oxygen

• Start: glucose, 2 ATP, 2 NAD+, 4 (ADP + Pi)

• End: 2 NADH, 2 ATP (net), 2 Pyruvate

Intermediate step: Acetyl Coenzyme A (CoA) Formation

• Takes place in the mitochondria

• Go through twice, once for each pyruvate

• Start: 2 pyruvate, 2 NAD+, 2 CoA

• End: 2 NADH, 2 acetyl-CoA, 2 CO2

Krebs Cycle (Citric Acid)

• Takes place in mitochondria (inner compartment)

• Go through twice, once for each acetyl-CoA

• Start: 2 acetyl-CoA, 6 NAD+, 2 FAD, oxygen

• End: 2 ATP, 6 NADH, 2 FADH2, 4 CO2, coenzyme A

Aerobic

• 36-38 ATP

• Oxygen required

• Complete oxidation

• End-product: water

Anerobic

• 2 ATP (glycolysis)

• No oxygen required

• Not complete oxidation

• End-product: lactate comparison

Oxidative Phosphorylation

• Hydrogen carriers NADH and FADH2 (from previous steps) enter the electron transport system (ETS)

• Electrons from hydrogen are passed along a system of enzymes within the mitochondria producing 34 more molecules of ATP

– Note: possible loss of up to 2 ATP due to transport of NADH from cytosol into mitochondria = 32 net

• Oxygen is required

ATP Totals

• Glycolysis 2 ATP (net)

• Krebs cycle 2 ATP

• ETS/Chemiosmosis 32 ATP (net)

• Totals 36 ATP per glucose

Anaerobic Fermentation

• Takes place in the cytoplasm; doesn’t require oxygen or mitochondria

• End-product: lactate

Lactate Fermentation

• Also called lactic acid fermentation

• Some lactate fermenters spoil food while others preserve it.

• Lactobacillus and acidophilus digest lactose in milk to make cheese and yogurt.