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Describe the gross structure of the human gas exchange system and how we breathe in and out - AQA - A-Level Biology - Question 10 - 2018 - Paper 1
Question 10
Describe the gross structure of the human gas exchange system and how we breathe in and out. --- The human gas exchange system consists of several key structures t... show full transcript
Worked Solution & Example Answer:Describe the gross structure of the human gas exchange system and how we breathe in and out - AQA - A-Level Biology - Question 10 - 2018 - Paper 1
Step 1
Describe the gross structure of the human gas exchange system
Answer
The human gas exchange system consists of several key structures that facilitate the process of breathing and gas exchange. These include:
- Trachea: This is the main airway that connects the throat to the lungs. It branches into two main bronchi.
- Bronchi: These are the two large air passages that lead from the trachea to the lungs. Each bronchus further divides into smaller bronchi and bronchioles.
- Bronchioles: These are smaller branches of the bronchi that lead to the alveoli.
- Alveoli: These are tiny air sacs where the actual gas exchange occurs. They are surrounded by capillaries that facilitate the diffusion of oxygen and carbon dioxide.
Breathing Process
Breathing is an essential part of the gas exchange mechanism. The diaphragm and external intercostal muscles play crucial roles in this process:
- When we inhale, the diaphragm contracts and moves downward, and the external intercostal muscles contract, raising the rib cage. This increases the volume of the thoracic cavity.
- As the volume increases, the pressure inside the cavity decreases, creating a vacuum that allows air to flow into the lungs.
- Upon exhalation, the diaphragm and intercostal muscles relax, decreasing the thoracic cavity's volume, which increases the pressure and forces air out of the lungs.
Step 2
Mucus produced by epithelial cells in the human gas exchange system contains triglycerides and phospholipids. Compare and contrast the structure and properties of triglycerides and phospholipids.
Answer
Both triglycerides and phospholipids share common structural elements but serve different functions in biological systems:
- Composition: Both triglycerides and phospholipids contain glycerol and ester bonds formed by the reaction of glycerol with fatty acids.
- Fatty Acids: Triglycerides can possess saturated or unsaturated fatty acids, while phospholipids also contain one phosphate group. The presence of this phosphate group in phospholipids contributes to their unique properties.
- Hydrophobic and Hydrophilic Regions: Triglycerides are generally hydrophobic, as they do not mix with water. In contrast, phospholipids have both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions. The hydrophilic head interacts with water, while the hydrophobic tails are repelled by it.
- Functionality: Triglycerides serve primarily as energy storage, whereas phospholipids are critical components of cell membranes, forming bilayers that provide structure and regulate the movement of substances in and out of cells.
Step 3
Describe how lactose is formed and where in the cell it would be attached to a polypeptide to form a glycoprotein.
Answer
Lactose is formed through a reaction between glucose and galactose, which occurs via a condensation reaction. This process can be outlined as follows:
- Formation: Lactose is synthesized in the Golgi apparatus of cells through the enzyme lactase, which catalyzes the formation of the glycosidic bond between glucose and galactose.
- Glycoprotein Attachment: The newly formed lactose can be covalently attached to a polypeptide in the Golgi apparatus. The attachment occurs at specific sites on the polypeptide chain, typically at serine or threonine residues, allowing the protein to become a glycoprotein. This modification plays a crucial role in cell recognition and signaling.