Biology - Respiration in Humans

Question 1

What are organic compounds?

Answer 1

Organic compounds refer to carbon-containing compounds that are found in living organisms.

Question 2

What is cell respiration?

Answer 2

It refers to the controlled release of energy from organic compounds to produce adenosine triphosphate (ATP). ATP is formed from adenosine diphosphate (ADP) and phosphate ion using energy from respiration. ATP is not energy, but a molecule to store energy.

Question 3

What is respiratory substrate?

Answer 3

Organic compounds (e.g. glucose, lipids and proteins) that organisms consume and/or are present in their bodies can be used as a respiratory substrate to produce ATP, which is a source of energy to carry out the functions of life.

Question 4

What is oxidation of glucose?

Answer 4

During cell respiration, glucose will undergo oxidation which is a chemical reaction in which a molecule gains oxygen or loses hydrogen.

Question 5

What are the types of respiration?

Answer 5

Aerobic and anaerobic respiration.

Question 6

What is aerobic respiration?

Answer 6

The release of energy by the breakdown of
glucose in the presence of oxygen, carbon dioxide (respiratory gases) and water molecule as waste products, large amount of energy formed which is stored in ATP. Carried out in a series of steps that are catalysed by enzymes which are contained in mitochondria.
Glycolysis, Link reaction, Krebs cycle, Oxidative phosphorylation.
- some energy is released as heat, circulated around body by the blood to keep warm
- to support aerobic cell respiration, cells take in oxygen from their environment and carbon dioxide is returned to it in a process known as gas exchange

Question 7

What is glycolysis

Answer 7

• first stage in both aerobic and anaerobic cell respiration
• site of reaction is the cytoplasm
• specific enzyme catalyses each reaction in the pathway
• glucose as substrate, 2 molecules of pyruvate as product
• for each molecule of glucose used during glycolysis, there is a net gain of 2 ATP molecules
• oxygen is not required, carbon dioxide not produced

Question 8

What is the structural adaptation of mitochondria?

Answer 8

• double membrane encloses the organelle, with the outer layer forming a smooth continuous boundary
• outer mitochondrial membrane: separates contents of organelle from cytoplasm
• inner mitochondrial membrane: contains proteins and enzymes for oxidative phosphorylation
• cristae: increase the surface area for oxidative phosphorylation
• matrix: contains enzymes, site for Krebs cycle
• ribosomes: site of protein synthesis, including the synthesis of enzymes and proteins required for cellular respiration

Question 9

What is anaerobic respiration?

Answer 9

the breakdown of glucose in the absence of oxygen, releasing a small amount of energy. This occurs during vigorous activity when muscles cannot get enough oxygen for aerobic respiration, so anaerobic respiration kicks in to meet the increased energy demand. This leads to an oxygen debt—the extra oxygen required after exercise to remove lactic acid, which builds up and causes fatigue and cramps. Because of this, anaerobic respiration can’t be sustained for long. Only 2 ATP molecules are produced per glucose molecule during anaerobic respiration

Question 10

What is lactate fermentation in humans?

Answer 10

• Pyruvate (can be used in aerobic respiration) from glycolysis is converted to lactic acid
• Excess lactate from anaerobic respiration is transported by the blood to the liver and oxidised to be converted back to pyruvate
• Converted back into pyruvate in the presence of oxygen
• Occurs in the cytoplasm

Question 11

What is a respirator and its components?

Answer 11

Measures the rate at which an organism respires. Designed to measure the rate of uptake of oxygen by the organism.
Syringe filled with air: Introduce a fixed amount of air into the tube
Potassium hydroxide solution in both tubes: Absorbs carbon dioxide that is present in the air inside the tube (can be replaced with alkalis such as sodium hydroxide, soda lime)
Filter paper: Increase efficiency of carbon dioxide absorption
Manometer with coloured liquid: Movement in the liquid per minute toward tube B measures the rate of oxygen consumption
Rubber bungs: Seal the tubes to prevent changes in air volume not due to respiration
Metal cage: Keeps the organism in place and away from contact with the hydroxide solution.

Question 12

What is gas exchange?

Answer 12

Oxygen taken in through gas exchange for aerobic respiration. It is the uptake of oxygen from and the release of carbon dioxide to the environment.

Question 13

What is ventilation?

Answer 13

The process of pumping air to the respiratory surface to replace the air already present. Maintains concentration gradients for gas exchange to continue.

Question 14

What are the parts of the human ventilation system?

Answer 14

Two lungs in thorax. Air passages:
- nasal passages
- pharynx
- larynx
- trachea
- bronchi and bronchioles
- alveoli
Gas exchange system:
- thoracic cavity
- ribs
- diaphragm
- intercostal muscles

Question 15

Where are the lungs located?

Answer 15

enclosed in the thorax, an airtight chamber formed by the ribcage, intercostal muscles, with a domed floor, the diaphragm.

Question 16

What is the diaphragm?

Answer 16

a sheet of muscle attached to the body wall at the base of the ribcage, separating the thorax from the abdomen. made up of muscle and elastic tissue. when the diaphragm muscles contract, the diaphragm flattens downwards. when diaphragm muscles relax, the diaphragm arches upwards.

Question 17

What is pleural fluid?

Answer 17

Pleural membrane lines on the internal surface of the thorax, and secretes and maintains pleural fluid. It is a lubricating liquid that
protects the lungs from friction during breathing movements.

Question 18

What is the trachea?

Answer 18

The trachea (windpipe) is supported by a series of incomplete rings of
C-shaped cartilage, ensure that the trachea is always kept open, despite pressure changes in the lung. Air passes through the trachea after it is drawn through the nose. The membrane next to the lumen is the epithelium.

Question 19

What cells does the epithelium of the trachea consist of?

Answer 19

Goblet cells: secrete mucus to moisten the incoming air and trap dust particles and bacteria
Ciliated cells: have hair-like structures called cilia in their surfaces. The cilia beat mucus (trapped with dust and bacteria) up into the buccal cavity where it is swallowed into the oesophagus.

Question 20

What are the bronchi and bronchioles?

Answer 20

• Trachea divides into two bronchi (one per lung)
• Bronchi divide into smaller bronchioles, which divide into alveoli
• The walls of the bronchi and larger bronchioles have smooth muscles (allow the width of these airways to vary) and cartilage rings (strengthen and protect from collapse)

Question 21

What are alveoli?

Answer 21

Millions of air sacs in the lungs - larger surface area for diffusion of respiratory gases.
Thin layer of epithelium (single cell layer) - shorter diffusion distance, rapid diffusion
Inner surface covered with fluid - gases can dissolve first before diffusing
Dense capillary network around it - maintain concentration gradient
Elastic fibers in the walls - allow to expand and recoil easily during breathing

Question 22

What are the intercostal muscles?

Answer 22

External and internal intercostal muscles found between the ribs.
- Antagonistic

Question 23

What happens to the thoracic cavity during inhalation?

Answer 23

1. External intercostal muscles: contracts
2. Internal intercostal muscles: relaxes
3. Rib cage: moves up and out
4. Diaphragm: contracts and flattens
5. Abdominal muscles: relax
6. Volume of thorax: increases
7. Pressure in thorax: decreases (below atmospheric pressure)
8. Air enters the lungs, inflates the alveoli, stretching the elastic fibers in the tissue

Question 24

What happens to the thoracic cavity during exhalation?

Answer 24

1. External intercostal muscles: relaxes
2. Internal intercostal muscles: contracts
3. Rib cage: drops to original position
4. Diaphragm: relaxes
5. Abdominal muscles: contracts
6. Volume of thorax: decreases
7. Pressure in thorax: increases (above atmospheric pressure)
8. Air leaves the lungs, elastic recoil of the lung tissue helps to facilitate this

Question 25

What is the path of air into the lungs?

Answer 25

External nostrils –> nasal passages –> pharynx –> larynx –> trachea –> bronchi –> bronchioles –> alveoli

Question 26

What is emphysema?

Answer 26

A condition in which the walls between individual alveoli break down, reducing the surface area of the alveoli available for gas exchange. Caused by long term exposure to airborne irritants, e.g. cigarette smokes. Tar in tobacco smoke causes white blood cells to secrete an enzyme which breaks down elastic fibres in the alveoli. Area for gas exchange decreases - difficulty getting sufficient oxygen in blood. Alveoli become less elastic –> difficult to ventilate the lungs. Irreversible damage.