RESPIRATION AND GAS EXCHANGE

Key concepts Types of respiration

Cellular Respiration is the chemical breakdown of food substances to yield ATP. Different organisms use different kinds of breathing mechanisms in order to

transport oxygen throughout their bodies. Evolutionary adaptations of gas exchange systems and respiration

Different plant adaptations in acquiring CO2 from the environment evolved: C3, C4, and CAM pathways.

Structural adaptations of respiratory apparatus depend on the animal’s habitat. The three most common respiratory organs are gills, tracheae, and lungs.

The respiratory system and circulatory system cooperate directly with each other.

Mammalian respiration The respiratory system is divided into the upper respiratory tract (nasal

passages, mouth, throat, larynx and trachea) and lower respiratory tract (bronchi and the lungs).

Air enters (inhalation) the respiratory system due to a pressure drop inside the lungs (negative pressure).

Air exits (exhalation) the respiratory system due to an increase in pressure inside the lungs.

Breathing is regulated by control centers in the brain (medulla oblongata and pons)

Gases are transported via passive diffusion throughout the body. Respiratory diseases and their prevention

Respiratory disorders may be congenital or environmental. Respiratory disorders can be prevented through a combination of proper diet

and lifestyle change.

Vocabulary words aerobic respiration air sacs alveolus anaerobic respiration asthma blood pH Bohr shift breathing bronchiole bronchus C3 pathway C4 pathway CAM pathway cell respiration countercurrent exchange cutaneous respiration diaphragm dissociation curve

emphysema epiglottis gas exchange gills glottis glycolysis hemocyanin hemoglobin larynx (voicebox) lung Cancer lungs medulla oblongata myoglobin nasal cavity negative pressure breathing nose parabronchi partial pressure

pharynx photosynthesis pharynx pneumonia pons positive pressure

breathing residual volume respiratory medium respiratory pigments respiratory surface rib muscles spiracle surface tension syrinx thoracic cavity tidal volume trachea or windpipe tracheae tuberculosis ventilation vital capacity vocal cords of the

larynx

Cellular Respiration- Transformation of chemical energy into ATP- Overall Reaction: C6H12O6 +6O2 → 6CO2 +6H2O + 36 ATP

1 Glucose molecule (6C) from digestionGlycolysis in the

cytoplasm 2 pyruvate

molecules (3C)2 ATPsAerobic

Respiration in the

mitochondriaKrebs Cycle

(2 ATPs)Electron

Transport Chain

(32 ATPs) CO2+ H2O

Anaerobic

Respiration in the cytosol ethanol/

lactic acid/CO2

NADH and FADH2 are e- donors that enable the formation of ATP

Photosynthesis Method of converting

sun energy into chemical energy usable by cells

Light reactions Dark

reactions/Calvin Cycle

6 CO2 + 6 H2O + light energy → C6H12O6 + 6O2

Plant adaptations for acquiring CO2 from the environment C3 (most abundant)

CO2 converted to a 3C sugar, 3-phosphoglycerate RuBisCO (Ribulose-1,5-bisphosphate

carboxylase/oxygenase) enzyme catalyzes carbon fixation

prone to photorespiration, lessens efficiency of food production during hot and dry days

C4 store CO2 in specialized compartments convert CO2 into a 4C compound, oxaloacetate converted into the 3C sugar and CO2 used in the C3

pathway/Calvin cycle minimizes photorespiration and enhances sugar

production

CAM succulent plants f ix CO2 at night and store it as 4C organic acids minimizes water loss and enhances sugar production

Gas exchange supplies oxygen for cellular respiration and removes CO2 Gas exchange – uptake of O2

from environment and discharge of CO2

Mitochondria need O2 to produce more ATP, CO2 is the by-product

C6H12O6 + 6O2 6CO2 + 6H2O + 36 ATP

Diffusion rate α SA large α 1/d2 thin

Moist so gases are dissolved first

DIFFUSION

Respiratory surfaces and gas exchange Respiratory

surface Size of organism Habitat Metabolic demands

Unicellular organisms Entire surface area

for diffusion

Simple invertebrates Sponges,

cnidarians, flatworms, roundworms

diffusion

Respiratory surfaces and gas exchange More complex

animals Thin, moist

epithelium Separates medium

from capillaries Entire outer skin Extensively folded

and branched respiratory organs

Gills in aquatic animals Outfoldings of the

body surface suspended in water

Sea stars Segmented worms or

polychaetes Molluscs and

crustaceans Fishes Young amphibians Total surface area is

greater than the rest of the body

Water as a respiratory medium Adv - Surfaces are

kept moist Disadv - O2

concentrations in water are low

Ventilation – increasing flow of respiratory medium over the surface

Countercurrent exchange – process in which two fluids flow in opposite directions, maximizing transfer rates

Why are gills impractical for land animals?

Just keep swimmin

g swimmin

g swimmin

g!

Air as a respiratory medium Adv - Air has a

higher concentration of O2

Adv - O2 and CO2 diffuse much faster in the air less ventilation

Disadv - Difficulty of keeping surface moist

Solution: respiratory infolding inside the body

Tracheal system of insects – network of tubes that bring O2 to every cell

Spiracles

Lungs Heavily vascularized

invaginations of the body surface restricted to one location

Found in spiders, terrestrial snails, vertebrates

Amphibians supplement lung breathing with skin

Turtles supplement lung breathing with moist surfaces in mouth and anus

Mammalian respiration

Lung ventilation through breathing

Positive pressure breathing in frogs

“Gulping in” air

Negative pressure breathing in reptiles and mammals

Rib muscles and diaphragm change lung volume and pressure

Lung volumes Factors

Sex Height Smoking Physical activity Altitude

Tidal volume Volume of air inhaled

and exhaled with each breath

Vital capacity Maximum volume

inhaled and exhaled during forced breathing

Residual volume Air left in alveoli after

forced exhalation

Avian breathing• Air sacs - bellows

to keep air flowing through the lungs

• Syrinx – vocal organ of birds

Control centers in the brain regulate breathing

Gases diffuse down pressure gradients

concentration and pressure drives the movement of gases into and out of blood

Respiratory pigments Low solubility of O2 in

H2O Respiratory pigments

are proteins with metal atoms Hemoglobin – Fe Hemocyanin – Cu Allow reversible

binding of O2 Cooperativity Drop in pH results

in a lowered affinity of hemoglobin for O2

Respiratory pigments

CO2 transport 7% in plasma 23% bound to

hemoglobin 70% as HCO3- *

*buffers resist pH changes

Fetal hemoglobinHbF has greater affinity to O2 than Hb

low O2% by time blood reaches placenta fetal Hb must be able to bind O2 with

greater affinity than maternal Hb

Deep-diving mammals Seals, whales, dolphins are capable of long underwater dives

Weddell seal 5% O2 in lungs, 70% in blood

Huge spleen stores huge volumes of blood

Large concentrations of myoglobin in muscles

Heart rate and O2 consumption rate decrease

Blood is redirected from muscles to brain, spinal cord, and eyes

Respiratory disorders Asthma – chronic

inflammatory lung disease

Bronchitis – inflammation of bronchi (chronic/acute)

Emphysema – damage to alveoli

Cystic fibrosis – abnormality in mucus producing glands

Pneumonia – lung inflammation

Tuberculosis – airborne chronic bacterial infection

Lung cancer – normally begins in bronchi, usually carcinomas