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Questions and Answers
What is a primary function of membrane proteins acting as channels or transporters?
What is a primary function of membrane proteins acting as channels or transporters?
What distinguishes the cell wall composition of fungi from that of plants?
What distinguishes the cell wall composition of fungi from that of plants?
Who coined the term 'cell' after observing cork in the mid-1600s?
Who coined the term 'cell' after observing cork in the mid-1600s?
Which component of the cytoplasm provides mechanical support, anchors organelles, and aids in the movement of substances?
Which component of the cytoplasm provides mechanical support, anchors organelles, and aids in the movement of substances?
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Which of the following structures is associated with motility in cells, specifically in sperm cells?
Which of the following structures is associated with motility in cells, specifically in sperm cells?
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What did Rudolf Virchow contribute to cell theory?
What did Rudolf Virchow contribute to cell theory?
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What is the primary function of the rough endoplasmic reticulum?
What is the primary function of the rough endoplasmic reticulum?
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Which of the following statements is NOT a principle of cell theory?
Which of the following statements is NOT a principle of cell theory?
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Which cell type is characterized by the presence of a membrane-bound nucleus?
Which cell type is characterized by the presence of a membrane-bound nucleus?
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What is contained within the nucleus of a cell?
What is contained within the nucleus of a cell?
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Which part of the Golgi apparatus is involved in packaging and shipping substances in the cell?
Which part of the Golgi apparatus is involved in packaging and shipping substances in the cell?
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What theory describes the origin of eukaryotic cells from symbiotic bacteria?
What theory describes the origin of eukaryotic cells from symbiotic bacteria?
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What role do centrioles play within the cell?
What role do centrioles play within the cell?
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Which statement correctly describes the role of membrane proteins?
Which statement correctly describes the role of membrane proteins?
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What is a characteristic feature of prokaryotic cells?
What is a characteristic feature of prokaryotic cells?
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Which component makes up the plasma membrane structure?
Which component makes up the plasma membrane structure?
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Study Notes
Introduction to Cells
- Cells are the smallest living units of structure and function in all organisms.
- Most cells are microscopic.
- The cell is a basic unit of life.
Discovery of Cells
- Robert Hooke (mid-1600s) observed "row of empty boxes" in cork and coined the term "cell."
Cell Theory
- (1839) Theodor Schwann & Matthias Schleiden proposed that "all living things are made of cells."
- (50 years later) Rudolf Virchow stated that "all cells come from cells."
Principles of Cell Theory
- All living things are made up of cells.
- The cell is the smallest living unit of structure and function of all organisms.
- All cells arise from preexisting cells (disproving spontaneous generation).
Cell Size
- Typical plant cell size is 10-100 μm.
- Chloroplast size is 2-10 μm.
- Hen's egg is 65 mm.
- Mitochondrion is 1-5 μm.
- Trypanosoma (protozoan) is 25 μm long.
- Human red blood cell is 7-8 μm diameter.
- HIV (AIDS virus) is 100 nm.
- Poliovirus is 30 nm.
- DNA molecule is 2 nm diameter.
Cells Have Large Surface Area-to-Volume Ratio
- A small cell has a larger surface area compared to its volume, which is important for efficient exchange of materials with its surroundings.
- Larger cells (with a smaller surface area to volume ratio) have challenges regarding efficient exchange of nutrients or waste produced.
Characteristics of All Cells
- Cells have a surrounding membrane.
- Cells contain protoplasm (cell contents in thick fluid).
- Cells contain organelles (structures for cell function).
- Cells contain a control center with DNA.
Cell Types
- Prokaryotic cells
- Eukaryotic cells
Prokaryotic Cells
- First cells to evolve.
- Found in bacteria and archaea.
- Do not have a nucleus or membrane-bound organelles
- Nucleoid region is where the DNA is concentrated.
Eukaryotic Cells
- Contain a nucleus and membrane-bound organelles.
- Found in fungi, protists, plants, and animals
- Possess many organelles
Representative Animal Cell
- Contains various organelles like the nucleus, mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, centrioles, microtubules, and microfilaments.
Representative Plant Cell
- Contains a cell wall, chloroplasts, and a large central vacuole in addition to the organelles often found in animal cells.
Organelles
- Cellular machinery.
- Two general kinds:
- Derived from membranes
- Bacteria-like organelles
Bacteria-Like Organelles
- Derived from symbiotic bacteria.
- Ancient association.
- Endosymbiotic theory: Modern cells evolved from cells and symbiotic bacteria.
Plasma Membrane
- Double layer of phospholipids and proteins.
- Contains cell contents.
Phospholipids
- Polar head: hydrophilic (attracts water).
- Nonpolar tail: hydrophobic (repelled by water).
- Interacts with water; forms a bilayer.
Movement Across the Plasma Membrane
- Small, uncharged molecules (like water, carbon dioxide, and oxygen) can move freely.
- Carrier proteins transport certain molecules (e.g. glucose, ions).
- Fluid mosaic model describes the lipid bilayer with proteins incorporated in it.
Membrane Proteins
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- Channels or transporters: Move molecules in one specific direction.
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- Receptors: Recognize particular chemical signals.
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- Glycoproteins: Identify cell type.
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- Enzymes: Catalyze chemical reactions for producing substances.
Cell Walls
- Found in plants, fungi, and many protists.
- Surrounds the plasma membrane.
- Composed of different materials (e.g., cellulose in plants, chitin in fungi).
Cell Wall Differences
- Plant cell walls are primarily cellulose.
- Fungi cell walls contain chitin.
Cytoplasm
- Viscous fluid containing organelles and other cytosol components such as interconnected filaments and fibers
- Stores substances.
Cytoskeleton
- Filaments and fibers.
- Made of 3 fiber types: Microfilaments, Microtubules, Intermediate filaments.
- 3 functions: Mechanical support; anchor organelles; help move substances.
Cilia & Flagella
- Provide motility.
- Cilia: Short, used to move substances outside human cells.
- Flagella: Whip-like extensions, found on sperm cells.
- Both contain basal bodies that are like centrioles.
Cilia & Flagella Structure
- Bundles of microtubules with plasma membrane.
- Specific arrangement of microtubules (9 pairs of microtubules around the central 2 microtubules).
Centrioles
- Pairs of microtubular structures.
- Play a role in cell division.
Membranous Organelles
- Functional components within the cytoplasm.
- Bound by membranes (e.g., mitochondria, ER, Golgi apparatus, lysosomes, vacuoles).
Nucleus
- Control center of cell.
- Double membrane (nuclear envelope)
- Contains chromosomes and nucleolus.
Nuclear Envelope
- Separates nucleus from the rest of the cell.
- Double membrane
- Has nuclear pores.
DNA
- Hereditary material.
- Chromosomes - DNA and proteins; involved in cell division.
- Chromatin - DNA in the cell.
Nucleolus
- Most cells have 2 or more nucleoli.
- Directs synthesis of RNA within the nucleus.
- Forms ribosomes.
Endoplasmic Reticulum
- Helps move substances within cells.
- Network of interconnected membranes.
- Two types:
- Rough ER (with attached ribosomes)
- Smooth ER (without ribosomes)
Rough Endoplasmic Reticulum
- Ribosomes attached to its surface, which manufactures proteins.
- Modifies proteins from ribosomes.
Smooth Endoplasmic Reticulum
- No attached ribosomes
- Has enzymes that help build carbohydrates and lipids.
Golgi Apparatus
- Involved in synthesis of plant cell wall.
- Packaging and shipping station of cell.
- Modifies, sorts, and packages proteins for secretion or other cellular use.
- Molecules come in vesicles.
- Vesicles fuse with Golgi membrane.
- Molecules may be modified by Golgi.
- Molecules pinched-off in separate vesicles.
- Vesicle leaves Golgi apparatus.
- Vesicles may combine with plasma membrane to secrete contents.
Lysosomes
- Contain digestive enzymes.
- Functions in cell renewal, breaking down old cell parts, and digesting invaders.
Vacuoles
- Membrane-bound storage sacs.
- More common in plants than in animals.
- Contains water, food, and wastes.
Mitochondria
- Have their own DNA.
- Bound by double membrane.
- Break down fuel molecules (cellular respiration) – glucose, fatty acids.
- Release energy (ATP).
Chloroplasts
- Derived from photosynthetic bacteria.
- Solar energy-capturing organelles
- Double membrane
- Contain chlorophyll.
- Site of photosynthesis.
Photosynthesis
- Takes place in the chloroplast.
- Makes cellular food (glucose).
Review of Eukaryotic Cells (Table)
- Provides a summary of eukaryotic cell structures and functions.
Comparison of Bacterial, Animal, and Plant Cells (Table)
- Provides a comparison of external and internal cellular structures found in bacteria, animal, and plant cells highlighting their presence/absence.
Questions and Answers
- A section for questions and answers related to cell biology concepts.
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Description
Test your knowledge on the fundamentals of cell biology in this quiz on the Introduction to Cells. Explore the history of cell discovery, the principles of cell theory, and various cell sizes and types to deepen your understanding of this essential unit of life.
