GCSE Biology: Respiration, Photosynthesis, Homeostasis, and Pathogens

According to the magnification triangle and conversion diagram, what is the formula to calculate image size, and how do you convert millimetres ($\text{mm}$) to micrometres ($\mu\text{m}$)?

$\text{Image size} = \text{actual size} \times \text{magnification}$; to convert from millimetres to micrometres, multiply by $1000$.

How is homeostasis defined in the notes?

The process of the body maintaining a constant internal environment (the conditions and "stuff" inside the body).

What three internal conditions are controlled by homeostasis in the human body?

Blood sugar (glucose) levels, water levels, and body temperature.

How does the body physically respond when exposed to cold conditions?

The body responds by shivering and causing blood vessels to constrict (vasoconstriction).

Which major blood vessels and anatomical structures are associated with the liver and digestive circulation?

The inferior vena cava, aorta, hepatic artery, hepatic portal vein, gall bladder, and common bile duct.

What is the formula used to calculate a person's safe maximum heart rate during exercise, and what is the value for a $45$-year-old person?

$\text{Safe maximum heart rate} = 220 - \text{age in years}$; for a $45$-year-old, it is $220 - 45 = 175\,\text{beats per minute}$.

Why does a person's skin turn red and their breathing rate increase during vigorous exercise?

Arteries dilate to direct blood near the surface to lose heat, while breathing rate increases and deepens to supply more oxygen to the blood and working muscles.

What is the balanced chemical symbol equation for aerobic respiration?

$$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$$

In which cellular organelle does aerobic respiration take place, and why is the reaction classified as exothermic?

It takes place in the mitochondria; it is classified as exothermic because it releases energy to the surroundings.

What is the word equation and balanced chemical formula for anaerobic respiration in human muscle cells?

$\text{Glucose} \rightarrow \text{lactic acid}$ ($C_6H_{12}O_6 \rightarrow 2C_3H_6O_3$)

In which cellular compartment does anaerobic respiration occur, and during what timeframe of exercise is it primarily used?

It occurs in the cytoplasm of cells and is primarily used during the first $1\text{ to }2\,\text{minutes}$ of exercise.

What is oxygen debt?

The amount of extra oxygen required by the body after exercise to react with and remove the accumulated lactic acid.

What is the word equation and chemical formula for anaerobic respiration (fermentation) in yeast and plant cells?

$\text{Glucose} \rightarrow \text{ethanol} + \text{carbon dioxide}$ ($C_6H_{12}O_6 \rightarrow 2C_2H_5OH + 2CO_2$)

What are five key ways green plants utilize the glucose produced during photosynthesis?

1. Respiration (to release energy)\n2. Making cellulose (for strong cell walls)\n3. Making proteins (glucose combined with nitrate ions to form amino acids)\n4. Storing as insoluble starch (main chemical storage)\n5. Storing as lipids (fats and oils)

In a leaf starch test using iodine, why does an area covered with black paper fail to turn blue-black?

The black paper blocks light from reaching the leaf, preventing photosynthesis from occurring; without photosynthesis, no starch is produced to react with the iodine.

Why might a greenhouse tomato grower increase carbon dioxide concentration to $0.08\%$ rather than a higher concentration?

Atmospheric concentration is $0.04\%$, and increasing it to $0.08\%$ increases the rate of photosynthesis and plant growth; raising it higher would cost more money without increasing the rate further because another factor (such as light or temperature) becomes limiting.

What is the chemical symbol equation for photosynthesis, and why is it classified as endothermic?

$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$; it is endothermic because it absorbs light energy from the environment.

How is the rate of photosynthesis measured in an experiment using pondweed and sodium hydrogen carbonate solution?

By placing pondweed in sodium hydrogen carbonate solution at a set distance from a light source and counting the number of oxygen bubbles produced in $1\,\text{minute}$.

What is the definition of a limiting factor in photosynthesis?

Any environmental condition in short supply that prevents the rate of photosynthesis from occurring at its maximum level (e.g., light intensity, $CO_2$ concentration, or temperature).

Why does the rate of