Cell Organelles
Name the structure that encloses all the organelles of a cell.
Cell membrane
Define active transport.
Movement of molecules from an area of low concentration to an area of high concentration. ATP is required.
When is the rate of photosynthesis highest during the day?
Midday - most sunlight available for photolysis (light-dependent reaction)
What is the photosynthesis word equation?
carbon dioxide + water → glucose + oxygen (in the presence of sunlight)
Name the steps of aerobic respiration. For an extra 100 points, where do the steps occur?
1. Glycolysis - cytoplasm
2. Krebs' Cycle - mitochondrial matrix
3. Electron Transport Chain - inner mitochondrial membrane (cristae)
Name three cell structures that are only found in plant cells. For an extra 50 points, describe the role of each structure.
Cell wall - for support
Chloroplasts - site of photosynthesis
Large central vacuole - stores cell sap, maintains turgor pressure
What is the difference between passive diffusion and osmosis?
Osmosis refers to the movement of water, while diffusion is the movement of any other small, uncharged molecules.
What happens to enzymes in extreme conditions?
Active site denatures - peptide bonds between amino acids break down. Loss of shape means substrates can no longer bind.
Oxygen, ATP, NADPH
(H+ ions are produced which bind to electron carrier NADP+).
What is the chemical equation for anaerobic respiration? For an extra 50 points, what is the word equation for lactic acid fermentation?
Aerobic: C6H12O6 + 6O2 → 6CO2 + 6H2O
Lactic acid fermentation: glucose → lactic acid + ATP
Name an adaptation of a root hair cell.
Long protrusions increase surface area for water and nutrient absorption.
Name the three levels of tonicity and describe them.
Isotonic - equal concentration of solute and solvent Hypotonic - high conc. solvent, low conc. solute
Hypertonic - low conc. solvent, high conc. solute
What is a rate-limiting factor?
A substance that is in low supply. It slows down the rate at which a reaction can occur, even if other substances are abundant.
What is the Calvin Cycle?
Carbon dioxide is 'fixed' and converted into glucose through a series of enzyme-mediated steps.
What is ATP used for in the cell?
Active transport, chemical reactions, movement (e.g., muscle contractions).
Name an adaptation of the mitochondria for efficient respiration.
Cristae - folding of the inner membrane increases surface area for the ETC.
Why do animal cells burst in a hypotonic solution, but plant cells don't?
Why does enzyme activity plateau?
The chemical reaction stops increasing and levels off because all enzyme active sites are fully occupied by substrate molecules.
Oxygen diffuses into the spongy mesophyll via stomata.
Water diffuses into the plant via the root hair cells, and is transported to the leaves through the xylem.
Name an advantage of aerobic respiration and anaerobic respiration.
Anaerobic: Fast energy production in the absence of oxygen (only glycolysis stage).
Name two structures in a chloroplast and explain how they are adapted for efficient photosynthesis.
Membrane - transparent to allow sunlight to be absorbed
Grana - stacks of thylakoids to increase surface area
How does a protein pump work?
1. Substrate (charged molecule) binds to pump on one side of the membrane
2. ATP binds, causing the pump to change conformation
3. Pump releases substrate on other side of the membrane, allowing movement of molecule from high to low concentration.
Name the enzymes used in DNA replication and describe their functions.
Helicase - separates DNA strands
Primase - makes RNA primers to start building fragments
Ligase - joins Okazaki fragments together
Polymerase - adds complementary nucleotides to form the replicated strand
How does temperature affect the rate of photosynthesis?
Increasing temp. causes rate of photosynthesis to increase. However, extreme temperatures may cause enzymes involved in both steps of photosynthesis to denature.
What is the proton gradient in the ETC?
There is a low concentration of H+ ions in the matrix and a high concentration outside the matrix. Electrons are pumped from a low to a high conc. to make ATP.