(6) Exchange Flashcards
Explain Mechanism of breathing that causes air to enter the lungs:
(Inspiration)
Diaphragm contracts
and is flattened
External Intercostal Muscles contract and ribcage is pulled up and out
Thoracic Cavity
Volume increases
Pressure decreases
Describe how the structure of the insect gas exchange system:
-Provides cells with sufficient oxygen
-Limits water loss
Spiracles, Trachea, Tracheoles.
Spiracles:
Allow diffusion of oxygen. Hairs around spiracles reduce water loss
-Can close so less water loss
Tracheoles:
Highly Branched, so larger surface area for exchange.
Walls are thin for short diffusion pathway. Walls are permeable to oxygen.
Exoskeleton:
Impermeable to reduce water loss
Describe the pathway by an oxygen molecule from alveolus to blood.
1.Oxygen diffuses across alveolar epithelium
2.Diffuses to Capillary Endothelium lining the capillary
Oxygen binds to haemoglobin in red blood cells.
How do respiratory gases move in and out of the tracheal system: (Insects)
(3 Ways)
(1) Along a diffusion gradient: Respiring cells use up oxygen which creates concentration gradient. (Vice Versa for CO2)
(2) Muscle contractions squeeze tracheae, moving air in and out rapidly.
(3) Ends of the tracheoles are filled with water:
During periods of major activity: Muscle cells near the ends of the tracheoles produce lactate. Reducing water potential in muscle cells. Water moves into cells, reducing volume of water in tracheoles so more space for air
This increases diffusion speed but leads to more water evaporation
Describe how gills in fish are adapted for efficient gas exchange.
(1) Gill lamellae are at right angles to the gill filaments which are stacked creating a large surface area.
(2)Counter-current flow: Water and blood flow in opposite directions to maximize oxygen diffusion.
Describe the process of counter-current exchange in the gills of fish. (4marks)
Blood and water flow in opposite directions across the gill lamellae (1).
Water with a higher oxygen concentration meets blood with a lower oxygen concentration, allowing oxygen to diffuse into the blood (1).
As water moves along the gill lamellae, it continuously encounters blood with an even lower oxygen concentration, maintaining a constant diffusion gradient (1).
This ensures that oxygen uptake occurs efficiently across the entire length of the gill lamellae, maximizing oxygen absorption into the bloodstream (1).
Explain Mechanism of breathing that causes air to leave the lungs:
(Expiration)
Diaphragm relaxes
External intercostal muscles relax and internal contract.
Thoracic Cavity volume decreases
Pressure in lungs increases
Explain How Different Enzymes Cause Protein Digestion:
Peptidases (proteases) hydrolyse proteins into amino acids.
Endopeptidase enzymes hydrolyse the peptide bonds between amino acids in the centre of the protein to produce smaller polypeptides
Exopeptidase enzymes hydrolyse the peptide bonds at the ends of polypeptide molecules, (formed by endopeptidase) releasing dipeptides and amino acids.
Dipeptidase enzymes hydrolyse peptide bonds in dipeptides to form amino acids
Describe The Absorption Of triglycerides:
Lipase enzymes hydrolyse the ester bonds of triglyceride molecules.
This creates monoglycerides and fatty acids.
Monoglycerides and fatty acids emulsify with bile salts to form micelles.
This makes fatty acids + monoglycerides more water soluble.
Micelles hydrolyse when in contact with outside of epithelial cell.
Releasing monoglycerides and fatty acids
Monoglycerides and fatty acids are small, non polar, lipid soluble molecules. Hence diffuse through phospholipid bilayer down conc. gradient
Monoglycerides + Fatty acids transported to SER.
Where they are recombined to form triglycerides.
Triglycerides transported to Golgi apparatus. Modified & combined with lipoproteins and cholesterol to form chylomicrons.
Describe the structure and their functions of the human lungs.
Trachea:
Flexible airway,
C shaped rings of cartilage
Prevents trachea collapse as air pressure falls during inspiration.
Trachea walls lined with ciliated epithelia and goblet cells.
Goblet cells secrete mucus trapping pathogens
Ciliated epithelium cells have cilia extending from cell membrane. Beating of cilia causes mucus to move to throat.
Bronchi:
Also have cartilage, ciliated epithelium cells and goblet cells.
Bronchioles
Cartilage, Smooth muscle: when smooth muscle relaxes bronchioles widen to allow more air to pass in.
Alveoli:
Sites of gas exchange
wall of alveolus and wall of blood capillary - one cell thick/Short diffusion pathway.
Extensive capillary network means once oxygen is diffused into blood it is rapidly carried away by alveoli maintaining a steep concentration gradient for oxygen
Describe Carbohydrate Digestion:
Mouth
Salivary amylase: hydrolyses starch → maltose.
Mineral salts maintain neutral pH (optimum for amylase).
Stomach
Acidic conditions denature salivary amylase, preventing any further hydrolysis of starch
Small Intestine (Duodenum & Ileum)
Pancreatic amylase:
Continues the hydrolysis of any remaining starch to maltose
Alkaline salts from pancreas & intestine maintain neutral pH.
Membrane-bound maltase (on epithelial cells of ileum) hydrolyses maltose → α-glucose, which is absorbed into the blood by Co-Transport.
Describe the Adaptations of the Small Intestine for Absorption:
Villi & Microvilli – Increase surface area, maximising diffusion and active transport.
Thin Epithelium – Short diffusion pathway, increasing absorption efficiency.
Muscular Contractions – Maintain diffusion gradients by moving intestinal contents, ensuring fresh digestion products replace absorbed ones.
Rich Blood Supply – Maintains a concentration gradient by transporting absorbed molecules away.
Microvilli on Epithelial Cells – Further increase surface area for absorption.
