Cell Communication
Name the four main types of receptors for signaling molecules.
The four main types of receptors are: ligand-gated ion channels, G protein-coupled receptors, receptor tyrosine kinases, and intracellular receptors.
Explain the structure of the phospholipid bilayer.
The phospholipid bilayer is a double layer of phospholipids with hydrophilic heads facing outwards and hydrophobic tails facing inwards, forming a semi-permeable barrier.
What are the three products of cellular respiration?
Water, ATP, and carbon dioxide
What is the role of chlorophyll a in photosynthesis?
Chlorophyll a is the primary pigment in chloroplasts that absorbs light energy and initiates the electron transport chain in photosynthesis.
Distinguish between exergonic and endergonic reactions.
Exergonic reactions release energy (negative ΔG), while endergonic reactions require energy input (positive ΔG).
What is the difference between mitosis and meiosis?
Mitosis is a process of cell division that produces two genetically identical daughter cells, while meiosis produces four genetically distinct haploid cells.
What is the role of ligand-gated ion channels in cell signaling?
Ligand-gated ion channels open or close in response to a signaling molecule, allowing ions to flow across the membrane and triggering a cellular response.
How does facilitated diffusion differ from simple diffusion?
Facilitated diffusion involves the movement of molecules across the membrane through protein channels or carriers, while simple diffusion occurs directly across the lipid bilayer without the aid of proteins.
Where does pyruvate oxidation occur?
In the matrix of the mitochondria
Describe the three phases of the Calvin cycle.
Phase 1: Carbon fixation (CO2 is combined with RuBP by Rubisco)
Phase 2: Reduction (ATP and NADPH are used to convert 3-PGA to G3P)
Phase 3: Regeneration of RuBP.
Explain the concept of activation energy.
Activation energy is the minimum energy required to start a chemical reaction. Enzymes lower the activation energy.
Explain the events that occur during the S phase of the cell cycle.
During the S phase, the cell's DNA is replicated, producing two identical copies of each chromosome.
What is apoptosis ?
Cell death or suicide
Explain the role of aquaporins in water transport.
Aquaporins are water channel proteins that facilitate the passive transport of water across the cell membrane.
Free Pi attaches to ADP where?
In the ATP synthase
Discuss the process of photorespiration
Photorespiration occurs when the enzyme Rubisco binds oxygen instead of CO2, leading to a wasteful cycle. C4 and CAM plants have adaptations to concentrate CO2 around Rubisco, minimizing photorespiration.
What is the role of enzymes in chemical reactions, and how are they regulated?
Enzymes are biological catalysts that lower the activation energy of reactions by providing a favorable environment. They can be regulated by inhibitors, activators, and feedback mechanisms.
Describe the events that occur during the M phase of the cell cycle.
The M phase includes mitosis, where the replicated chromosomes are segregated into two daughter cells, followed by cytokinesis, where the cytoplasm divides to form two separate cells.
Describe the mechanism of G protein-coupled receptors.
G protein-coupled receptors bind to a signaling molecule, causing a conformational change that activates a G protein, which then activates downstream effector proteins.
Describe the process of exocytosis and its importance in cellular function.
Exocytosis is the process by which cells secrete molecules (e.g., hormones, enzymes) by fusing vesicles containing the molecules with the plasma membrane and releasing their contents.
Which step produces the MOST amount of ATP? and identify the final electron acceptor in this process.
Oxidative phosphorylation or chemiosmosis.
O2 is the final electron acceptor.
What is the role of the enzyme Rubisco during the Calvin cycle? And what phase does that takes place in?
Rubisco is the enzyme that catalyzes the initial carbon fixation reaction in the Calvin cycle, combining CO2 with RuBP.
Explain the concept of free energy and its relationship to spontaneous and non-spontaneous reactions.
Free energy is the energy available to do work in a system. Spontaneous reactions have a negative change in free energy (ΔG < 0), while non-spontaneous reactions have a positive change in free energy (ΔG > 0).
What is the role of checkpoints in the cell cycle?
Checkpoints in the cell cycle ensure that the cell is ready to proceed to the next phase, preventing errors or damage from being propagated. These checkpoints can trigger cell cycle arrest or apoptosis if problems are detected.
Explain the mechanism of action of intracellular receptors in cell signaling.
Intracellular receptors are located in the cytoplasm or nucleus and bind to hydrophobic signaling molecules (e.g., steroid hormones) that can diffuse across the cell membrane. The ligand-receptor complex acts as a transcription factor, regulating gene expression.
Discuss the role of the sodium-potassium pump in maintaining the membrane potential.
The sodium-potassium pump is an active transport system that maintains the electrochemical gradient across the cell membrane by pumping sodium ions out and potassium ions in, using energy from ATP. This gradient is essential for many cellular processes, including nerve impulse conduction and nutrient uptake.
What is the purpose of the citric acid cycle? And what step of Cellular respiration is it?
The citric acid cycle is the third step of cellular respiration, where the acetyl group from pyruvate is oxidized, releasing CO2, NADH, FADH2, and a small amount of ATP.
Name the adaptations that minimize photorespiration
CAM and C4 plants
Explain the laws of thermodynamics and their relevance to biological systems.
The first law states that energy cannot be created or destroyed, only transformed.
The second law states that entropy (disorder) increases in any spontaneous process, making the energy less available to do work.
What is the significance of the G2 phase in the cell cycle?
The G2 phase is the final phase of the cell cycle before mitosis, where the cell checks for any errors or damage in the replicated DNA and prepares for cell division.