Plasma Membrane and Cytoplasm
What separates the cell from the external environment?
The plasma membrane
Which organelle stores the genetic information of the cell?
The nucleus
Which organelles are called the βpowerhousesβ of the cell?
Mitochondria
Which organelles are characteristic of plant cells?
Plastids
What is the smallest structural and functional unit of a living organism?
The cell
What is the main function of the plasma membrane?
It protects the cell and regulates the movement of substances into and out of the cell.
Where does protein synthesis take place?
On ribosomes
What is the function of lysosomes?
They digest and break down unnecessary substances and damaged cell structures.
Which plastids carry out photosynthesis?
Chloroplasts
What term describes organisms whose cells have a nucleus enclosed by a membrane?
Eukaryotes
A cell is placed in a solution with a higher concentration of dissolved substances than inside the cell. What will happen to the cell, and why?
Water will move out of the cell by osmosis, causing the cell to shrink.
A cell produces large amounts of proteins that will be secreted outside the cell. Which organelles are especially important for this process? Explain their roles.
The nucleus contains the genetic information; ribosomes on the rough ER synthesize proteins; the ER transports them; the Golgi apparatus modifies, sorts, and packages them for secretion.
What is the function of the Golgi apparatus?
It modifies, sorts, packages, and transports substances.
What is the main function of chromoplasts, and where can they be found in plants?
Chromoplasts contain pigments that give color to flowers, fruits, and other plant parts.
Which structures are found in both plant and animal cells? Name at least three.
The plasma membrane, cytoplasm, nucleus, ribosomes, mitochondria, endoplasmic reticulum, and Golgi apparatus.
Why is the phospholipid bilayer important for the functioning of the plasma membrane? Explain how its structure determines what can pass through it.Ρ
The hydrophobic interior of the phospholipid bilayer prevents many charged and water-soluble substances from passing freely, while small nonpolar molecules can pass more easily. Membrane proteins help transport specific substances.
Predict what would happen to protein production if ribosomes were removed from a cell while the nucleus and endoplasmic reticulum remained intact.
Protein synthesis would stop or decrease dramatically because ribosomes are the structures that assemble amino acids into proteins. The genetic information would remain in the nucleus, but it could not be translated into proteins.
What is the role of the centrosome (cell center)?
It participates in cell division and helps form the spindle apparatus.
A plant cell contains many chloroplasts. What does this suggest about the function of the cell? Explain your answer.
The cell is likely actively involved in photosynthesis because chloroplasts contain chlorophyll and absorb light energy.
Why are organelles separated from each other inside a eukaryotic cell?
Membrane-bound organelles create separate compartments where different chemical reactions can occur efficiently and under suitable conditions.
A cell membrane loses its selective permeability. Predict at least two consequences for the cell and explain why they may lead to cell death.
The cell will lose control over the movement of ions, water, and other substances. Ion concentrations and water balance will become disrupted, cellular processes will fail, and the cell may eventually die.
Compare the roles of the nucleus, ribosomes, and rough endoplasmic reticulum in protein synthesis. Why must these structures work together?
The nucleus stores DNA and provides the genetic instructions; ribosomes translate the instructions into proteins; the rough ER provides a site for synthesis of many proteins and their transport. They work together to convert genetic information into functional proteins.
Why can damage to mitochondria lead to cell death?
Because ATP production decreases, causing the cell to lack sufficient energy for vital processes.
A cell contains stored starch grains, but it does not have chloroplasts. What type of plastid could be responsible for storing these substances? Explain its function.
Leucoplasts. They are colorless plastids that store nutrients such as starch, oils, and proteins.
A scientist observes a cell under a microscope. The cell has a cell wall, chloroplasts, and a large central vacuole. What type of cell is it? Explain how each of these structures helps the cell.
It is a plant cell. The cell wall provides support and protection, chloroplasts carry out photosynthesis, and the large central vacuole stores water and dissolved substances and helps maintain cell pressure.