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

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 digestion

Glycolysis in the cytoplasm

2 pyruvate molecules (3C)

2 ATPs

Aerobic Respiration in the mitochondria

Krebs 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 swimming swimming swimming!

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 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 hemoglobin

HbF 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