Cell Structure and Function
What are the three parts of the cell theory?
The cell theoryglossary term (opens in a new window) has three main components:
- All living things are made of one or more cells.
- The cell is the basic unit of structure, physiology, and organization in living things.
- Every cell arises from a pre-existing cell.
What are the differences between prokaryotic and eukaryotic cells?
Cells can be classified as prokaryotic or eukaryotic. Prokaryotic and eukaryotic cells have different structures:
- Prokaryotic cells have no membrane-bound nucleus, unlike eukaryotic cells. Instead of a nucleus, prokaryotic cells have an unenclosed region of DNA called the nucleoid.
- Prokaryotic cells’ DNA strands are typically circular, while eukaryotic cells’ DNA strands are linear.
- Prokaryotic cells have no membrane-bound organelles, in contrast to the many types of organelles in eukaryotic cells.
What structures make up cells?
Cells have different subcellular parts based on their function and the organism in which they are found:
- All cells have DNA, a cell membraneglossary term (opens in a new window), cytoplasm, and ribosomes.
- A prokaryotic cellglossary term (opens in a new window) has a nucleoid and may also contain plasmids, thylakoids, a cell wall, a capsule, and flagella.
- A eukaryotic cellglossary term (opens in a new window) typically has a nucleus, Golgi apparatus, mitochondriaglossary term (opens in a new window), endoplasmic reticulum, and one or more vacuoles. A plant cellglossary term (opens in a new window) also has a cell wall and chloroplasts.
- All cells have an internal network of filaments called a cytoskeletonglossary term (opens in a new window) that helps transport materials within the cell, supports the cell, and plays a role in cell division. A eukaryotic cytoskeleton is composed of structures called microtubules, microfilaments, and intermediate filaments.
What are the differences between plant and animal cells?
Plant and animal cells have different structures:
- Plant cells have cell walls, which provide support but also prevent plant cells from moving. In contrast, animal cells do not have cell walls, and therefore many animal cells can move.
- Plant cells have chloroplasts, which allow photosynthesis to occur. Animal cells do not have chloroplasts.
- Each plant cell typically has a single large vacuole. Animal cells tend to have smaller, and sometimes multiple, vacuoles.
What is the role of mitochondria in eukaryotic cells?
Mitochondria are important organelles in eukaryotic cells. They have a distinct structure and function:
- Mitochondria have two membranes. The inner membrane is folded so that it provides a large surface area for chemical reactions.
- Mitochondria supply energy to the cell through cellular respiration, in which oxygen combines with food molecules to release energy in the form of ATP.
What is the structure and function of the cell membrane?
All cells are surrounded by a cell membrane, which separates the inside of the cell from the surrounding environment:
- The cell membrane is made of a two-layered sheet of phospholipids embedded with proteins.
- Each phospholipid is composed of a “water-loving” head and two “water-fearing” tails. The tails point inward to the interior of the membrane, while the head points outward.
- Ion channels transport ions across the cell membrane through passive transport, and ion pumps transport ions across the membrane through active transport.
