Bio HL Gas exchange & Transport

Why do we need systems for gas exchange?

As the Surface area:Volume ratio decreases, our body volume is too large for diffusion to be efficient. We need specialized structures

Features of efficient gas exchange

1. Large surface area

2. thin layers

3. moist surface

4. permeability

5. concentration gradient

why large surface area important for gas exchange

large domain for exchange

why thin layers good for gas exchange

short path for diffusion

why moist surface good for gas exchange

dissolves gases like oxygen so they can diffuse

How is concentration gradient maintained in mammals during gas exchange

Ventilation and a dense network of blood vessels

Trachea

Brings O2 from nasal cavity into lungs

• cartialage prevents collapse

• incomplete rings makes it flexible

• ciliated epithelial & goblet cells prevent bacteria (do we need to know this?)

Bronchus

Y shaped structure that connects trachea to lungs

bronchioles

Branches of the bronchus

• smaller diameter helps slow down air flow

Alveoli

small air sacs where gas exchange occurs

• thin layers of epithelial cells

• elastic fibers give recoil

Alveolar fluid

Helps gases dissolve in the alveoli

• secreted by type II pneumocytes

surfactant

Prevents surface tension from alveolar fluid from making alveoli collapse

Inspiration process

1. diaphragm contracts, flattens & moves downwards

2. external intercostal muscles move up & outwards

3. thoracic volume increases, so thoracic cavity pressure decreases

4. air flows into lungs

expiration process

1. Diaphragm relaxes & moves upwards, returning to its dome shape

2. external intercostal muscles move down & in

3. thoracic volume decreases, thoracic pressure increases

4. air flows out

forced expiration process

• diaphragm pushed up into a higher dome shape

• internal intercostal muscles contrcact

• rib cage moves down & in forcefully

tidal volume

volume of air coming in or out of lungs in each normal breath

• measured from peak to trough on spirometer

vital capacity

the maximum amount of air a person can expel from the lungs after taking a very deep breat

• measured peak to trough

breathing rate

number of breaths per minute

oxygen uptake

rate a person uses oxygen (dm³/min)

• height of slope on spirometer

inspiratory & expiratory reserve

how much extra air you can breath in and out based on vital capacity

residual volume

how much more air you could hypothetically breath out after exhaling to your vital capacity

total capacity

residual volume + vital capacity

main organs of gas exchange in a plant?

leaves

plants adaptations for gas exchange?

• thin & flat leaves

• waxy cuticle covering the upper epidermis keeps insides moist

• stomata regulates exchange on underside of epidermis

• air spaces in spongy mesophyll allow gases to diffuse easier

• vascular bunder (xylem & phloem) maintains transport of nutrients, maintaining concentration gradient

stomata

small pores on underside of leaf that regulate gas exchange

• open & close using guard cells

• primary site of water loss

transpiration

water loss due to evaporation on under side of plant when the stomata open

factors affecting transpiration rate

• number of leaves

• stomata density & distribution

• waxy cuticle thickness

• high temperature (molecules evaporate faster)

• humidity - slower diffusion

• wind intensity - increases diffusion

• light intensity - makes stomata open wider

haemoglobin

protein in red blood cells that transport oxygen from lungs to the rest of the body

• quartenary stucture

• contains 4 polypeptide chains that have a haem group with iron that bind to oxygen

• can bind to 4 oxygen molecules in total

• oxyhaemoglobin when bound to oxygen

adult haemoglobin

2 alpha & 2 beta polypeptide chains

cooperative binding

When oxygen binds to the haemoglobin subunit, its conformation changes. Its affinity for oxygen increases, and when oxygen is released, affinity decreases.

• ex: affinity lowest in muscles but highest in lungs

Bohr shift

when carbon dioxide binds to haemoglobin in tissues with low pH (acidic due to excercise), it changes its conformation leading to a decrease in oxygen affinity.

• enables haemoglobin to drop off O2 in respiring muscles that need it

fetal haemoglobin

2 alpha & 2 gamma particles

• higher affinity for oxygen because theres less available in placenta

Types of blood velles

1. arteries

2. arterioles

3. capillaries

4. venules

5. veins

capillaries

Exchange substances between the blood and surrounding tissues through its thin endothelial wall.

• smallest blood vessel

• some have gaps to increase efficiency

arteries

carry blood away from heart to rest of body

• high pressure

• elastin & smooth muscle

• aorta is the biggest one

arterioles

connect arteries to capillaries

occlusion of coronary arteries

when the coronary arteries that branch off aorta & supply heart muscle with O2 get blocked by plaque

• caused by fatty diet or high blood pressure

veins

return blood to the heart

valves

structures in veins that prevent the backflow of blood

Xylem

transports water & dissolved minerals

Phloem

transports carbon compounds like sugar & amino acids

transport process in xylem

1. plant root cells pump minerals into xylem, causing water to enter via osmosis

2. opening of stomata at leaves causes transpiration, creating negative pressure at top of plant

3. suction from transpiration pulls water up stem to leaves. Water can make a chain because of cohesion & adhesion

adaptations of xylem for water transport

• lignin gives rigidity & hydrophobia

• transports water unidirectionally

• contains pits, areas without lignin where water can move across adjacent cells

tissue fluid

Diffuses through capillary, allowing dissolved molecules from blood to enter bodies cells. Also carries waste back into the blood

• Diffuses through capillaries in the arteries, and is reabsorbed into the blood by the veins

lymphatic system

small portion of tissue fluid doesnt return to capillaries, but form a lymph

• where white blood cells destroy harmful bacteria

• return to bloodstream after purified

double circulatory system

blood passes through heart twice

pulmonary cycle

blood goes from heart to lungs, then back to the heart

systemic cycle

blood goes from the heart to the rest of the body

flow of the blood through the heart

1. deoxygenated blood enters the vena cava

2. enters the right atrium

3. goes through tricuspid valve into the right ventricle

4. goes through pulmonary valve

5. goes into pulmonary artery

6. blood sent to the lungs

7. blood returns from the lungs through the pulmonary vein

8. blood enters left atrium

9. blood goes through the bicuspid valve into the left ventricle

10. blood goes through the aortic valve into the aorta

11. blood sent to the rest of the body

three stages of the cardiac cycle

1. atrial systole

2. ventricular systole

3. diastole

atrial systole

Basically when blood enters ventricles

1. atria contracts, increasing pressure

2. tricuspid & bicuspid valves open

3. blood enters the ventricles

4. openings to large veins (vena & pulmonary) close to prevent backflow

5. pressure in atria decreases because the ventricles are now full

ventricular systole

Basically when blood enters arteries from ventricles

1. ventricle muscles contract

2. pressure in ventricles increase

3. tricuspid & bicuspid valves close

4. pulmonary & aortic valves open, & blood enters arteries

5. pressure in ventricles decrease

diastole

when the heart muscle relaxes & ventricles begin to refill with blood

• bicuspid & tricuspid valves open

two types of nodes

sinoatrial (SA) & atrioventricular (AV)

Sinoatrial nodes

start atrial systole by telling atria to contract. Signal travels down to atrioventricular node

atrioventricular node

signal from SA node reaches AV node. It travels through the bundle of His and along Purkinje fibers in the ventricle walls to initiate contraction

• activates ventricular systole

• there is a slight delay when it receives signal from AV node to allow blood to finish pumping into ventricles

root pressure

solutes transported into the roots of plant, causing water to enter root hairs via osmosis

• hydrostatic pressure forces water up stem

• used when transpiration is not possible (ex: night, or 100% humidity)

Structure of phloem

made of sieve tube elements, plasmodesmata, & companion cells

translocation

transport of a plant’s “food” (sugar, amino acids) from a source to a sink using the phloem.

source

where carbon compounds are created in a plant

sinks

parts of plant that stores carbon compounds

• ex: developing fruits

cardiac cycle

• . Atrial Systole (Contraction): Left atrium contracts → pressure rises → bicuspid (AV) valve opens → blood enters left ventricle.

• 2. Early Ventricular Systole: Ventricle contracts → ventricular pressure exceeds atrial pressure → bicuspid valve closes (prevents backflow).

• 3. Isovolumetric Phase: All valves closed briefly → ventricle contracts forcefully → ventricular pressure spikes dramatically.

• 4. Ventricular Ejection: Ventricular pressure exceeds aortic pressure → aortic semilunar valve opens → blood pumped into aorta at high pressure.

• 5. Ventricular Diastole (Relaxation): Ventricle relaxes → pressure drops below aortic pressure → aortic valve closes (prevents backflow).

• 6. Passive Filling: Ventricular pressure drops below atrial pressure → bicuspid valve reopens → blood flows passively to restart cycle.