Robert Hooke and the Discovery of Cells
What was Robert Hooke studying that led him to the discovery of cells? Robert Hooke was studying cork under a microscope, and when he observed the tiny, box-like structures, he coined the term "cells" to describe them.
What is the origin of the word “cell”? The word "cell" comes from the Latin word "cella," meaning "small room," which Hooke used to describe the compartments he observed in cork.
Cell Theory
List the four parts of the cell theory.
- All living organisms are composed of one or more cells.
- The cell is the basic unit of life.
- All cells arise from pre-existing cells.
- Cells contain the hereditary information necessary for regulating cell functions and transmitting information to the next generation of cells.
Cell Size
Define prokaryotic – Prokaryotic cells are single-celled organisms that lack a nucleus and other membrane-bound organelles. Their DNA is circular and located in a region called the nucleoid.
Define eukaryotic – Eukaryotic cells are organisms whose cells contain a nucleus and other organelles enclosed within membranes. Their DNA is linear and organized into chromosomes.
Surface Area and Cell Growth
Why is surface area such a limiting factor to cell growth? Surface area limits cell growth because it affects the amount of material that can enter and exit the cell. As a cell grows larger, its volume (which needs resources) increases much faster than its surface area (which controls exchange with the environment), making it challenging for the cell to take in enough nutrients and remove waste.
Cell Membrane and Transport
Define plasma membrane (also called Cell Membrane)– The plasma membrane is a biological membrane that separates and protects the interior of all cells from the external environment. It regulates the movement of substances in and out of the cell.
Summarize the four functions of the plasma membrane.
- Barrier: Separates the inside of the cell from the outside environment.
- Selective Transport: Regulates what enters and leaves the cell.
- Communication: Contains receptors for signaling and interaction with other cells.
- Cell Recognition: Identifies the cell to other cells in the body.
What molecule makes up plasma membranes? Phospholipids primarily make up plasma membranes, along with proteins, cholesterol, and carbohydrates.
Label the hydrophobic and hydrophilic regions of the plasma membrane diagram. (Please visualize or draw these based on the standard phospholipid layout: The heads are hydrophilic and face outward towards the aqueous environments, while the tails are hydrophobic and face inward, away from water).
Give the function of each of these membrane proteins.
- Receptor: Binds to specific molecules (ligands) to trigger a response in the cell.
- Carrier: Transports substances across the membrane.
- Enzyme: Catalyzes biochemical reactions at the membrane surface.
- Anchoring: Provides structural support and helps to anchor the cell to its environment.
- Recognition: Identifies the cell type and allows for immune recognition.
What is the purpose of the carbohydrate chains found in cell membranes? Carbohydrate chains attach to proteins and lipids on the membrane's surface, serving as markers for cell recognition, signaling, and adherence to other cells.
Define selective permeability – Selective permeability is the ability of a cell membrane to allow certain substances to pass through while preventing others.
What passes through the membrane easily? Small nonpolar molecules (e.g., O₂, CO₂) and water can pass through the membrane easily.
What is not able to pass through the membrane without help? Large polar molecules (e.g., glucose) and ions typically require assistance (via transport proteins) to cross the membrane.
Define diffusion – Diffusion is the movement of particles from an area of high concentration to an area of low concentration until equilibrium is reached.
Why is diffusion considered passive transport? Diffusion is considered passive transport because it does not require energy (ATP) to occur; it relies on the natural motion of particles.
What is the concentration gradient? The concentration gradient refers to the difference in concentration of a substance between two areas, driving the movement of particles from higher to lower concentration.
Define osmosis – Osmosis is the diffusion of water across a selectively permeable membrane from an area of low solute concentration to an area of high solute concentration.
What determines the direction of water movement in osmosis? The direction of water movement is determined by the concentration of solute on either side of the membrane; water moves toward the area of higher solute concentration.
Label the area of low solute concentration, high concentration, and flow in this diagram. (Please visualize or refer to a diagram that typically illustrates the flow of water from low solute concentration to high concentration.)
Define and give an example of each of these types of solutions:
- Isotonic: Solutions with equal solute concentrations across a membrane (e.g., saline solution with similar salt concentration to human cells).
- Hypotonic: Solutions with a lower solute concentration than another solution (e.g., pure water leads to swelling of plant cells).
- Hypertonic: Solutions with a higher solute concentration than another solution (e.g., saltwater leads to shriveling of cells).
Define facilitated diffusion – Facilitated diffusion is the process by which molecules pass across the plasma membrane through cell membrane channels or carriers, requiring no energy.
Define active transport – Active transport is the movement of molecules against their concentration gradient, requiring energy (ATP).
What is vesicular transport? Vesicular transport is the movement of materials into or out of the cell using vesicles, which are small membrane-bound sacs.
What is the difference between exocytosis and endocytosis?
- Exocytosis: The process by which substances are released from the cell. Vesicles containing the substances fuse with the plasma membrane and release their contents outside the cell.
- Endocytosis: The process by which cells take in substances by engulfing them in a vesicle formed from the plasma membrane.
What cells use phagocytosis to take in large amounts of material? Macrophages and other immune cells use phagocytosis to engulf large particles, such as pathogens and debris.
Cell Anatomy
Define cytosol (aka cytoplasm) - Cytosol is the fluid portion of the cytoplasm, where organelles and cellular components are suspended, facilitating metabolic reactions and transport.
Define organelle – Organelles are specialized structures within a cell that perform distinct functions necessary for cellular operation, such as energy production, protein synthesis, or detoxification.
In this table, summarize the function of each of the support and movement structures of the cell.
| Structure | Function | |---------------|-------------------------------------------------------| | Cytoskeleton | Provides structural support and shape, facilitates movement. | | Microvilli | Increases surface area for absorption and secretion. | | Centriole | Involved in cell division, helping to organize the spindle fibers. | | Cilia | Move substances over the cell surface or propel the cell.| | Flagella | Propel cells through their environment. |
Summarize the function of each of the eukaryotic cell organelles.
| Organelle | Function | |----------------------|----------------------------------------------------| | Ribosome | Synthesize proteins by translating mRNA. | | Rough ER | Synthesizes and modifies proteins; studded with ribosomes.| | Smooth ER | Synthesizes lipids and detoxifies certain chemicals.| | Golgi | Modifies, sorts, and packages proteins and lipids for secretion or use within the cell. | | Secretory Vesicle | Transports materials to the cell membrane for exocytosis.| | Lysosome | Contains digestive enzymes to break down waste materials and cellular debris.| | Peroxisome | Contains enzymes for fatty acid oxidation and detoxification of harmful substances.| | Mitochondria | Produces ATP through cellular respiration (the cell's powerhouses).|
Summarize the function of each of the parts of the nucleus.
| Structure | Function | |--------------------|----------------------------------------------------| | Nuclear Envelope | Double membrane that encloses the nucleus and regulates passage of molecules in and out. | | Nuclear Pore | Allow selective transport of molecules in and out of the nucleus. | | Nucleolus | Produces ribosomal RNA (rRNA) and assembles ribosome subunits. | | Chromatin/Chromosomes | DNA is packaged; chromatin is uncondensed DNA, while chromosomes are condensed for cell division. |
Label each part of the cell below. (Refer to a diagram of a cell.)
Summarize the function of each of these structures found only in plant cells.
| Structure | Function | |--------------------|----------------------------------------------------| | Chloroplast | Conducts photosynthesis to produce glucose and oxygen using sunlight. | | Cell Wall | Provides rigid structure and protection; composed of cellulose. | | Plasmodesmata | Channels between plant cells that allow for transport and communication. | | Central Vacuole | Stores nutrients and waste products, maintains turgor pressure for structural support. |
Label each of the plant cell structures. (Refer to a diagram of a plant cell.)
Describe what happens to plant cells placed in each of these solutions:
- Hypotonic: Plant cells swell as water enters, but cell walls prevent bursting; turgor pressure increases.
- Isotonic: No net movement of water; the cell remains in an equilibrium state.
- Hypertonic: Water leaves the cell, causing the cell to shrink (plasmolysis) as the cell membrane pulls away from the cell wall.