Cell Structure and Organelles
What is the jelly-like substance inside a cell that holds the organelles in place?
The cytoplasm.
What is the simple sugar that cells use for energy?
Glucose.
What part of the cell is often referred to as the “selectively permeable barrier”?
The cell membrane.
True or False: Water can move freely across the cell membrane through a process called osmosis.
True.
What is the smallest unit of life?
The cell.
What is the function of ribosomes in the cell?
Ribosomes are responsible for synthesizing proteins by translating genetic information from mRNA.
What process do plants use to convert sunlight into chemical energy?
Plants use photosynthesis to convert sunlight into chemical energy, producing glucose and oxygen as end products.
What is the main function of the cell membrane?
The cell membrane controls what enters and exits the cell, maintaining the internal environment and providing selective permeability.
Define diffusion and explain whether it requires energy.
Diffusion is the movement of molecules from an area of high concentration to low concentration. It does not require energy, as it is a passive process.
Which type of cell lacks a nucleus: prokaryotic or eukaryotic?
Prokaryotic cells lack a nucleus, while eukaryotic cells have a nucleus containing their genetic material.
What is the function of the nucleus in eukaryotic cells, and what important molecule does it contain?
The nucleus controls cell activities by regulating gene expression and contains DNA, which stores the genetic information needed for cell function and reproduction.
During cellular respiration, glucose is broken down to produce energy. Name the three main stages of cellular respiration.
The three main stages of cellular respiration are glycolysis, the Krebs cycle (or citric acid cycle), and the electron transport chain.
What role do protein channels play in the cell membrane, and why are they important for cell function?
Protein channels allow specific molecules and ions to pass through the membrane, facilitating the movement of substances that cannot diffuse directly across the lipid bilayer. They are essential for controlling the cell’s internal environment.
What is the difference between passive and active transport across a cell membrane?
Passive transport does not require energy and moves molecules down their concentration gradient, while active transport requires energy (often in the form of ATP) to move molecules against their concentration gradient.
What theory explains the origin of mitochondria and chloroplasts in eukaryotic cells, and what is the main idea of this theory?
The endosymbiotic theory suggests that mitochondria and chloroplasts originated as free-living bacteria that were engulfed by an ancestral eukaryotic cell, eventually forming a symbiotic relationship.
What is the main difference between the rough endoplasmic reticulum (ER) and the smooth ER in terms of structure and function?
The rough ER has ribosomes on its surface and is involved in protein synthesis, while the smooth ER lacks ribosomes and is involved in lipid synthesis and detoxification.
What molecule is known as the “energy currency” of the cell, and in which organelle is most of this molecule produced?
ATP (adenosine triphosphate) is known as the energy currency of the cell, and most ATP is produced in the mitochondria.
Describe the structure of a phospholipid and explain how it contributes to the selective permeability of the cell membrane.
A phospholipid has a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails. This structure creates a bilayer where only certain molecules can pass, contributing to selective permeability.
What is osmosis, and why is it important for cells to control water movement across their membranes?
Osmosis is the passive movement of water across a membrane from an area of low solute concentration to high solute concentration. Controlling water movement is essential to prevent cells from swelling or shrinking due to imbalances.
What are prokaryotic cells, and how do they differ from eukaryotic cells in terms of internal structure?
Prokaryotic cells lack membrane-bound organelles and a defined nucleus, while eukaryotic cells have these structures, allowing for compartmentalization of cellular functions.
What is the primary function of the lysosome, and why is it sometimes called the “recycling center” of the cell?
The lysosome contains enzymes that break down waste materials, cellular debris, and foreign particles, allowing the cell to recycle these components.
Photosynthesis occurs in two main stages. Name these stages and briefly describe the primary purpose of each.
What is the role of cholesterol in the cell membrane, and how does it help maintain membrane stability?
Cholesterol helps to stabilize the membrane’s fluidity, making it less permeable to very small water-soluble molecules and preventing it from becoming too rigid or too fluid across temperature changes.
What is facilitated diffusion, and how does it differ from simple diffusion? Give one example of a molecule that uses facilitated diffusion to enter or leave the cell.
Facilitated diffusion is a type of passive transport where molecules move down their concentration gradient with the help of a protein channel or carrier. Unlike simple diffusion, it requires membrane proteins. An example is glucose entering the cell.
According to the endosymbiotic theory, which two organelles are believed to have originated from ancient prokaryotic cells, and what is one piece of evidence supporting this theory?
Mitochondria and chloroplasts are thought to have originated from prokaryotic cells. Evidence includes the fact that both organelles have their own circular DNA, similar to bacteria.