Gas Exchange in Plants and Humans Lecture

Vocabulary flashcards covering plant and human gas-exchange concepts, structures, adaptations, experiments, and health impacts from the lecture notes.

Gaseous exchange

Process of taking in O2 and releasing CO2 across a respiratory surface.

Photosynthesis equation

6CO2 + 6H2O → C6H12O6 + 6O2 (requires light).

Respiration equation

C6H12O6 + 6O2 → 6CO2 + 6H2O (releases energy).

Stomata

Minute pores in the leaf epidermis where gases enter and leave.

Guard cells

Paired cells that swell to open or shrink to close each stoma.

Spongy mesophyll cells

Loosely packed leaf cells forming the main internal gas-exchange surface.

Intercellular air spaces (leaf)

Large gaps among spongy cells allowing rapid diffusion of gases.

High surface area to volume ratio

Key feature of all gas-exchange surfaces that maximises diffusion.

Lenticels

Small pores in bark permitting gas diffusion in woody stems.

Net gas exchange

Overall movement of O2 and CO2 depending on light intensity and time of day.

Hydrogen carbonate indicator

pH dye turning yellow (high CO2), red/orange (atmospheric CO2) or purple (low CO2).

Alveoli

Microscopic air sacs in lungs where blood and air exchange gases.

Thorax

Body region between neck and abdomen housing lungs and heart.

Nostrils

External openings where air enters; hairs and mucus trap dust.

Nasal passages

Moist cavity that warms, moistens and filters incoming air.

Pharynx

Shared throat cavity leading air from nose to larynx.

Larynx

Voice box; passageway where vocal cords vibrate to make sound.

Trachea

Windpipe supported by C-shaped cartilage rings, carrying air to bronchi.

Bronchi

Two large air tubes branching from trachea, one to each lung.

Bronchioles

Fine airways arising from bronchi and ending in alveolar clusters.

Pleural membranes

Double moist layers encasing lungs and forming airtight seal.

Pleural fluid

Lubricating liquid in pleural cavity preventing lung–wall sticking.

Diaphragm

Dome-shaped muscle separating thorax and abdomen; flattens during inhalation.

Ribs

Bony cage protecting lungs; moved by intercostal muscles during breathing.

External intercostal muscles

Muscles that contract to raise ribs during inhalation.

Internal intercostal muscles

Muscles that contract to lower ribs during forced exhalation.

Ciliated epithelial cells

Tracheal lining cells whose beating cilia sweep mucus upward.

Goblet cells

Mucus-secreting cells trapping dust and microbes in airways.

Ventilation

Mechanical movement of air into (inhalation) and out of (exhalation) lungs.

Inhalation (inspiration)

Diaphragm contracts, rib cage rises, thoracic volume increases, air rushes in.

Exhalation (expiration)

Diaphragm relaxes, rib cage falls, thoracic volume decreases, air pushed out.

Diffusion gradient (alveoli)

High O2 and low CO2 in alveolus vs opposite in blood, driving diffusion.

Adaptations of alveoli

One-cell-thick walls, huge surface area, moist lining, rich blood supply.

Inspired air composition

Approx. 21 % O2, 0.04 % CO2, 79 % N2, variable water vapour.

Expired air composition

Approx. 16 % O2, 4 % CO2, 79 % N2, high water vapour.

Carboxyhaemoglobin

Stable compound formed when CO binds irreversibly with haemoglobin.

Nicotine (effect)

Increases heart rate and blood pressure; promotes cholesterol deposition.

Tar (effect)

Sticky mixture causing excess mucus, cilia damage and lung cancer risk.

Carbon monoxide (effect)

Reduces blood’s O2-carrying capacity by forming carboxyhaemoglobin.

Chronic bronchitis

Inflamed airways with excess mucus slowing gas exchange.

Emphysema

Destruction of alveolar walls, reducing surface area and causing breathlessness.

Lung cancer

Uncontrolled cell division in lung tissue often triggered by tar.

Coronary heart disease

Blockage of coronary arteries linked to nicotine and CO from smoking.

Effect of exercise on breathing

Physical activity raises breathing rate and depth to supply more O2.

Spirometer

Device measuring volume of air inhaled and exhaled.

Limewater CO2 test

Turns cloudy in presence of high carbon dioxide.

T-tube inhaled vs exhaled air experiment

Setup comparing CO2 levels using indicator solutions in two tubes.

Leaf thinness

Reduces diffusion distance, speeding gas movement in and out.

High stomatal density

Many stomata increase total gas exchange per leaf.

Flat leaf shape

Maximises surface area and maintains concentration differences.

Internal air spaces (advantage)

Faster CO2 and O2 diffusion in air than through cells or water.

Moist internal surface (leaf)

Allows gases to dissolve before entering or leaving cells.

C-shaped cartilage rings

Structural support in trachea keeping airway open during breathing.

Antagonistic intercostal muscles

External and internal sets that perform opposite actions for breathing.

Atmospheric vs lung pressure

Air moves from higher to lower pressure; basis of ventilation.

Pulmonary artery

Vessel bringing CO2-rich, O2-poor blood to lung capillaries.

Haemoglobin

Red blood cell protein that binds O2 in lungs and releases it in tissues.

Pleural cavity

Thin, fluid-filled space between pleural membranes enabling lung movement.