What is the cell’s defining role in living organisms?
It is the smallest structural and functional unit of life.
What makes a cell the smallest structure capable of sustaining life?
It can carry out all processes necessary for life.
What does an open system exchange with its surroundings?
Both matter and energy.
Why are living cells open systems?
They exchange matter and energy with their surroundings.
What does the nucleus contain and regulate?
It contains DNA and regulates many cell activities.
What do ribosomes build?
Proteins.
What does the Golgi apparatus do to proteins and lipids?
It modifies, sorts, and packages them.
What carries a secreted protein from the rough ER to the Golgi?
A transport vesicle.
Which four elements are abbreviated CHON in biological molecules?
Carbon, hydrogen, oxygen, and nitrogen.
What are carbohydrates built from?
Simple sugars.
What are two energy-related functions of carbohydrates?
They provide energy and energy storage.
What are lipids often made from?
Glycerol and fatty acids.
What are two functions of lipids?
Long-term energy storage and insulation.
What are proteins built from?
Amino acids.
What are two functions of proteins?
Structure and catalysis by enzymes.
What are nucleic acids built from?
Nucleotides.
What does selective permeability help a membrane maintain?
Relatively stable internal conditions called homeostasis.
What is the main structure of a cell membrane?
A phospholipid bilayer.
How are phospholipid heads and tails oriented in a membrane?
The hydrophilic heads face the watery fluids, while hydrophobic tails point inward.
What does the fluid mosaic model describe?
A flexible phospholipid bilayer containing proteins and other molecules that can move within it.
Which substances usually cross directly through the membrane bilayer?
Small nonpolar molecules such as oxygen and carbon dioxide.
What is apoptosis?
Controlled programmed cell death in which a cell breaks itself down.
What role does apoptosis play in tissue health?
It removes damaged or unnecessary cells and supports normal growth and development.
What does the particle theory say all matter consists of?
Tiny particles.
What is true of particles in a pure substance?
They share identical basic properties.
What determines the spaces between particles?
The state of matter.
How does heating usually affect particle speed?
Particles usually move faster when heated.
How does passive transport differ from active transport in energy use?
Passive transport requires no direct ATP expenditure; active transport requires energy directly or indirectly.
In which direction does movement down a concentration gradient occur?
From higher to lower concentration.
What is diffusion?
The net movement of particles from higher to lower concentration due to random motion.
In which direction does water move during osmosis?
From higher to lower water concentration across a selectively permeable membrane.
How does an isotonic solution affect water movement and cell size?
There is no net water movement, and an animal cell stays about the same size.
What happens to animal and plant cells in a hypertonic solution?
An animal cell shrinks, while a plant cell may undergo plasmolysis.
How does a hypotonic solution affect water movement and animal cells?
Water moves into the cell, causing an animal cell to swell and possibly burst.
What is plasmolysis in a plant cell?
It is the shrinking of the membrane and cytoplasm away from the cell wall after water loss.
What is a protein pump?
An energy-using membrane protein that moves specific substances across a membrane.
Which ions does the sodium-potassium pump move into animal cells?
Potassium ions.
Which ions does the sodium-potassium pump move out of animal cells?
Sodium ions.
How does endocytosis bring material into a cell?
The membrane surrounds the material, folds inward, and forms an energy-requiring vesicle.
How does exocytosis release material outside a cell?
An energy-requiring vesicle fuses with the cell membrane and releases its contents.
What is the surface-area formula for a rectangular prism?
What is the volume formula for a rectangular prism?
How is the surface-area-to-volume ratio calculated?
Why are cells considered structural units of living things?
All living things are made of cells.
Why are cells considered functional units of living things?
They perform the processes needed to stay alive.
What is an organelle?
A specialized structure inside a cell that performs a specific job.
Which processes are included among cell life processes?
Intake, nutrition, growth, gas exchange, reproduction, movement, response to stimuli, and waste removal.
What cellular process do mitochondria carry out?
Cellular respiration, which produces most of the cell’s ATP.
What process do chloroplasts carry out?
Photosynthesis.
What do lysosomes digest?
Waste and old cell parts.
Which structures are absent from mature human red blood cells?
Nuclei.
What do channel proteins do in a cell membrane?
They form passages for substances to cross.
What role does cholesterol play in animal-cell membranes?
It helps regulate membrane fluidity and stability.
What do aquaporins allow to cross the membrane quickly?
Water, without using ATP to pump it.
How does random particle movement help explain diffusion?
It causes particles to spread through random motion.
What is osmosis?
Water movement across a selectively permeable membrane.
What does cell transport move across a cell membrane?
Substances entering or leaving a cell.
What is a concentration gradient?
A difference in a substance’s concentration between two areas.
What forces combine to form an electrochemical gradient?
Concentration forces and electrical forces.
Which gases can cross a cell membrane by simple diffusion?
Oxygen and carbon dioxide.
What is turgor pressure in a plant cell?
It is the pressure of the cell’s contents against the cell wall when water enters by osmosis.
How does turgor pressure help plant stems and leaves?
It helps them remain upright.
What happens to the vacuole during plasmolysis?
It becomes smaller as water leaves by osmosis.
How does a plant cell wall limit bursting when water enters?
The wall helps prevent the healthy plant cell from bursting.
What happens after a protein pump binds a substance?
It receives energy and changes shape to move the substance across the membrane.
What happens to a protein pump after moving a substance?
It returns to its original shape and can repeat the process.
What materials can exocytosis release?
Proteins, hormones, and neurotransmitters.
What does the surface area of an object measure?
The total area of its outside surfaces.
What does the volume of an object measure?
The amount of space it occupies.
How does cell size relate to the surface-area-to-volume ratio?
Smaller cells generally have a higher ratio than larger cells.
Through what surface do many substances enter and leave a cell?
The cell membrane.
What strategies can cells use to support exchange?
They can remain small, divide, or develop folds or extensions.
Answer 31 questions on Cell Transport and Surface Area.
1. Which description identifies a cell as the basic unit of life?
2. A living cell takes in nutrients and oxygen, releases waste and heat, and uses energy. Which system classification fits these exchanges?
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