Biology Chapter on Circulation and Ecosystems

The process by which organisms capture light energy and convert it into chemical energy (glucose) in the form of organic compounds.

The first stage of photosynthesis, where light energy is absorbed by chlorophyll and used to split water molecules, releasing oxygen and generating ATP and NADPH.

The second stage of photosynthesis, where carbon dioxide is fixed into glucose using the energy carriers (ATP and NADPH) produced in the light-dependent reaction.

The process by which cells break down glucose to release energy in the form of ATP.

The process by which organic molecules (glucose) are broken down in the absence of oxygen, producing a small amount of ATP and lactic acid or ethanol.

A process by which organisms obtain energy from inorganic compounds, such as hydrogen sulfide or ammonia, rather than sunlight.

A molecule that is the main energy currency of cells, used to power various cellular processes.

A type of chemical bond formed by the sharing of electrons between two atoms.

A type of chemical bond formed by the electrostatic attraction between oppositely charged ions.

A type of chemical bond formed by weak attractions between polar molecules, where a slightly positive end of one molecule is attracted to the slightly negative end of another molecule.

The lymphatic system collects fluid that leaks from blood vessels and returns it to the circulatory system. This fluid, called lymph, travels through lymphatic vessels and nodes, where it is filtered and cleansed. This process is vital for maintaining fluid balance, removing waste, and transporting immune cells.

During a cardiac cycle, the heart pumps blood in a specific sequence. The cycle begins with the right atrium receiving deoxygenated blood from the body and pumping it into the right ventricle. The right ventricle pumps the blood to the lungs for oxygenation. The oxygenated blood then enters the left atrium and is pumped into the left ventricle, which pumps it out to the body. This cycle repeats continuously.

Gas exchange occurs in the alveoli of the lungs. Oxygen from the inhaled air diffuses across the thin walls of the alveoli into the capillaries surrounding them, where it binds to red blood cells for transport to the body. Simultaneously, carbon dioxide from the blood diffuses across the alveoli walls and is exhaled. This process is driven by the difference in partial pressure of oxygen and carbon dioxide between the alveoli and the blood.

Air enters the lungs through the nasal passages, pharynx, larynx, trachea, bronchi, and finally the bronchioles, which lead to the alveoli. This pathway filters and warms the air before it reaches the lungs. Exhalation is simply the reverse process, with air moving through the same airways. The elasticity of the lungs and chest muscles helps create the pressure differences that allow air to move in and out.

Breathing is primarily controlled by the medulla oblongata in the brainstem. This center monitors the levels of carbon dioxide and oxygen in the blood and adjusts breathing rate and depth accordingly. When carbon dioxide levels rise, breathing becomes faster and deeper to remove excess CO2. Sensory receptors in the lungs also play a role, providing information about lung volume and airflow.