Cells, Organelles and Transport
What are the key structural differences between prokaryotic and eukaryotic cells?
Prokaryotic cells lack membrane‑bound organelles and a nucleus, while eukaryotic cells contain membrane‑bound organelles, including a nucleus that encloses the DNA.
Where does the citric acid cycle occur in the cell?
The citric acid cycle takes place in the matrix of the mitochondria.
What is the overall purpose of photosynthesis?
To convert light energy into chemical energy stored in glucose.
What is the main function of the digestive system?
To break down food and absorb nutrients
What wastes are removed by the excretory system?
Nitrogenous wastes and toxins (as well as excess ions and excess water).
What is the primary function of the endoplasmic reticulum?
The rough endoplasmic reticulum synthesizes proteins destined for secretion or membranes.
What are the main products of glycolysis?
Glycolysis produces pyruvate, ATP, and NADH.
Where do the light‑dependent reactions take place?
They occur in the thylakoid membranes of chloroplasts.
Which enzyme has an optimal pH of 3, and where does it act?
Pepsin, in the stomach
Where in the kidney would you find nephrons?
In the renal cortex
What does the fluid mosaic model describe?
It describes cell membranes as dynamic structures composed of a phospholipid bilayer with embedded proteins that can move laterally.
What role does the electron transport chain play in ATP production?
It transfers electrons through membrane proteins to create a proton gradient that drives ATP synthesis via chemiosmosis.
Guard cells are cells which surround pores on the leaf (stomata) and regulate the exchange of gases (including water vapour) in and out of the leaf.
How does the structure of the small intestine maximize absorption?
Villi and microvilli greatly increase surface area for absorption, enhancing nutrient uptake.
What is the function of the nephron?
It filters blood and forms urine through filtration, reabsorption, and secretion.
Why is selective permeability essential for cell survival?
It allows cells to maintain internal conditions by controlling which substances enter or leave, preserving homeostasis.
Why is oxygen essential for aerobic respiration?
Oxygen acts as the final electron acceptor, allowing continuous electron flow and regeneration of NAD⁺ and FAD.
What are the inputs and outputs of the light-independent reactions?
Input: CO2
Outputs: Glucose (and water, but less than what goes into the light dependent reaction).
What is the function of bile in digestion?
Bile emulsifies fats, increasing surface area for lipase action.
Where does most reabsorption occur in the nephron?
In the proximal convoluted tubule.
How does the structure of mitochondria support their role in ATP production?
Mitochondria have a highly folded inner membrane (cristae) that increases surface area for the electron transport chain, enhancing ATP synthesis.
How does fermentation differ from aerobic respiration in ATP yield and efficiency?
Fermentation produces far less ATP because it relies solely on glycolysis which produces only 2 ATP.
What is one factor that affects rates of photosynthesis in plants, and how?
Light intensity: the rate of photosynthesis increases with light intensity because more light energy is available to drive the light‑dependent reactions. At high light intensities, the rate eventually plateaus.
Carbon dioxide concentration: CO₂ is a substrate for carbon fixation in the Calvin cycle. When CO₂ is limited, the cycle cannot operate at maximum capacity.
Temperature: the reactions are enzyme‑controlled. As temperature rises, enzyme activity increases up to an optimum, after which the rate decreases due to enzyme denaturation.
Also: water availability (input), chlorophyll type and amount, leaf surface area
Digestive enzymes - help chemically digest food
Bicarbonate - neutralises chyme
Which part of the loop on Henle is impermeable to water? If it were permeable to water, how would its function change and how might this affect the urine produced?
Ascending loop
If the ascending limb were permeable to water, water would leave the tubule along with the ions. This would reduce the osmotic gradient around the nephron. The kidney would be much less able to reabsorb water in the collecting duct. The urine produced would be more dilute and larger in volume, reducing the body’s ability to conserve water.
OR, water would leave with the ions, creating a more concentrated urine