Exchange + Transport Flashcards
What is diffusion?
Diffusion is the movement of molecules from an area of high concentration to an area of low concentration due to random movement of molecules driven by kinetic energy.
What factors affect the rate of diffusion?
The factors affecting the rate of diffusion include:
- Steepness of the concentration gradient
- Temperature
- Surface area to volume ratio (SA:V), which decreases as organisms increase in size
- Properties of molecules (small, non-polar, uncharged molecules are fastest as they are soluble in the phospholipid bilayer)
- Thickness of the exchange surface
- Number of channel/carrier proteins available.
What is facilitated diffusion?
Facilitated diffusion is the movement of large, polar molecules or charged ions across a membrane, enabled by channel or carrier proteins.
What is the role of channel proteins in facilitated diffusion?
Channel proteins are water-filled and gated by specific stimuli. They control the movement of ions by changing shape.
What is the role of carrier proteins in facilitated diffusion?
Carrier proteins change shape to allow the passage of molecules. They may be open on one side of the membrane first.
What is osmosis?
Osmosis is the movement of water from an area of high water potential to an area of low water potential across a partially permeable membrane.
What is the water potential of water and solutions?
The water potential of pure water is 0, and the water potential of solutions is negative, measured in kilopascals (kPa).
What is a hypertonic environment?
A hypertonic environment has a higher concentration of solutes (a concentrated solution) outside the cell, causing water to move out of the cell, leading it to shrivel (crenate).
What is a hypotonic environment?
A hypotonic environment has a lower concentration of solutes (a dilute solution) outside the cell, causing water to move into the cell, leading to cell lysis.
What is an isotonic environment?
An isotonic environment has equal concentrations of solutes inside and outside the cell, resulting in no net movement of water.
What is active transport?
Active transport is the movement of substances from a low concentration to a high concentration using energy released by respiration. ATP is hydrolyzed to release energy to change the shape of the complementary carrier protein.
What is the importance of active transport?
Active transport is important for processes such as selective reabsorption in kidney tubules and absorption in the digestive tract.
What is co-transport?
Co-transport is the combination of facilitated diffusion and active transport, where the movement of certain molecules depends on each other.
How does co-transport work in the epithelium of the ileum?
In the ileum:
- Sodium ions (Na+) move into the cell via active transport, creating an Na+ concentration gradient.
- Sodium ions then move down the concentration gradient via facilitated diffusion, coupled with glucose molecules that are transported by co-transport proteins.
- This increases the glucose concentration inside the cell, creating a concentration gradient that allows glucose to move in by facilitated diffusion.
What is bulk transport?
Bulk transport is an active process involving the movement of large molecules into or out of the cell.
What is endocytosis?
Endocytosis is the movement of large molecules into the cell, where the cell membrane engulfs material and forms an endocytic vacuole around it. An example is phagocytosis (solid material) or pinocytosis (liquid material).
What is exocytosis?
Exocytosis is the movement of large materials out of the cell, where substances like enzymes or hormones are packaged into secretory vesicles that fuse with the cell membrane to release the substance.
Why is a gas exchange system necessary?
A gas exchange system is needed to:
- Supply oxygen to tissues for ATP production in respiration.
- Remove toxic waste products such as urea and carbon dioxide, which can alter the pH of cells.
How is metabolic rate measured?
Metabolic rate can be measured by carbon dioxide production, oxygen consumption, or heat production using respirometers, calorimeters, and oxygen/carbon dioxide probes.
What is the relationship between metabolic rate and mass?
Metabolic rate is directly proportional to mass.
What are the components of gas exchange tissues?
Key components include:
- Cartilage: Found in the trachea, prevents collapse, provides flexibility to withstand pressure of airflow.
- Ciliated epithelium: Contains cilia to sweep dust and pathogens away from the lungs.
- Goblet cells: Produce mucus to trap pathogens and dust.
- Smooth muscle: Found in the bronchi and bronchioles, can dilate (when more air needed) or constrict to regulate airflow.
- Capillary network: Allows gas exchange and maintains a steep concentration gradient. Capillaries are one cell thick, allowing for a short diffusion distance.
- Squamous epithelium: Very thin and permeable, aiding gas diffusion.
- Elastic fibres: Allow the lungs to recoil during expiration, making it a passive process.
What are the components of the trachea?
The trachea contains:
- C-shaped rings of cartilage to prevent collapse and provide flexibility and prevent friction with the oesophagus
- Lining of ciliated epithelium, smooth muscle, and elastic fibres.
- Mucus-producing cells.
What are the components of the bronchi?
The bronchi have:
- Full rings of cartilage for support.
- Thinner walls and a narrower lumen than the trachea.
What are the components of the bronchioles?
The bronchioles:
- Are lined with ciliated epithelium but lack goblet cells.
- Large bronchioles have smooth muscle and elastic fibres to control airflow.
- Smaller bronchioles do not have smooth muscle, becoming gradually smaller as they approach the alveoli.
What are the adaptations of alveoli for gas exchange?
Adaptations include:
- A large number of alveoli to increase surface area.
- A one-cell-thick epithelium for a short diffusion distance.
- An extensive capillary network for gas exchange and maintaining a steep concentration gradient.
- A liquid surfactant to provide surface tension preventing alveolar collapse.
- Moist walls to allow diffusion of gases.
- Oxygen concentration in the alveoli must be higher than in the blood causing air to move down a pressure gradient
How does air move into the lungs during inhalation?
During inhalation:
- The volume of the chest cavity increases, causing the pressure in the lungs to decrease (slightly lower than atmospheric pressure).
- The diaphragm contracts and flattens, providing space for the lungs to expand.
- The external intercostal muscles contract, moving the chest upwards and outwards.
- Air is drawn into the lungs from an area of higher pressure to an area of lower pressure.
What happens during exhalation at rest?
During exhalation at rest:
- The external intercostal muscles relax.
- The diaphragm relaxes and becomes dome-shaped.
- Elastic fibres in the alveoli cause air to be forced out passively due to the recoil of the lungs.
What happens during forced exhalation when exercising?
During forced exhalation:
- The internal intercostal muscles contract, pulling the ribs inwards and backwards.
- The abdominal muscles contract, pushing the organs up against the diaphragm, increasing pressure and forcing air out.
What is pulmonary ventilation rate (PVR)?
Pulmonary ventilation rate (PVR) is the total volume of air inhaled or exhaled per minute. It is calculated as:
PVR = tidal volume × breathing rate.
What is tidal volume?
Tidal volume is the volume of air inhaled per breath when at rest.
What is breathing rate?
Breathing rate is the number of breaths taken per minute.
What is vital capacity?
Vital capacity is the maximum amount of air that can be inhaled or exhaled in one breath.
What is oxygen uptake?
Oxygen uptake is the amount of oxygen used up in a given time.
How can spirometry be used to measure lung function?
Spirometry measures lung function by using a spirometer, which records the change in air volume as the person breathes as the total volume of air in the spirometer decreases as the person breathes. Carbon dioxide is absorbed by soda lime to prevent respiratory distress. A graph trace of breathing can be drawn
What does the graph trace from a spirometer show?
The graph trace from a spirometer shows the breathing pattern. As CO2 is removed, the total air available in the spirometer decreases,
reflecting oxygen uptake by the person.
What causes lung cancer?
Lung cancer is caused by mutations in oncogenes or tumour suppressor genes of bronchial epithelial cells, leading to a tumour in the lumen of airways. This tumour may obstruct airflow and squeeze against blood vessels or metastasise by entering the lymphatic system.
What are the symptoms of lung cancer?
Symptoms of lung cancer include:
- Shortness of breath
- Coughing up blood
- Shoulder and back pain (due to rib pivot)
- Sudden weight loss.
What is COPD?
Chronic Obstructive Pulmonary Disease (COPD) is a progressive disease where goblet cells become enlarged, producing excess mucus, and cilia are destroyed, leading to mucus buildup and bronchiole blockage. The condition causes scar tissue and infection which can attract phagocytes to the site which release the elastase enzymes that destroy the elastic fibres in alveolar walls and without this elastin the alveoli breaks down and bursts. This condition worsens over time.
How does smoking affect the lungs?
Smoking contributes to several lung diseases:
- Tar: A carcinogen that destroys cilia, causing bronchitis due to mucus buildup and emphysema by causing the breakdown and fusion of alveolar walls which reduces SA. It also increases the diffusion distance in alveoli by accumulating on alveolar walls.
- Nicotine: An addictive substance that narrows blood vessels.
- Carbon monoxide: Binds to red blood cells, preventing oxygen transport.
- Tobacco: carcinogen
Label the spirometers graph correctly
