Cells - introduction Flashcards
(23 cards)
State the three parts of the cell theory.
All living organisms are made up of one or more cells
Cells are the smallest units of life and are the basic functional unit in living organisms
New cells are produced from pre-existing cells
What is a cell?
Cells are the basic structural units of living organisms.
Why are stains used in microscopy when making temporary mounts?
Stains are used when making temporary mounts to provide colour contrast for cellular structures that might otherwise be transparent; this means that the structures can be seen under a microscope.
How is a coverslip used during preparation of a temporary mount of cells?
When making a temporary mount of cells a coverslip is gently lowered over a specimen after liquid and/or stain has been added.
How do electron microscopes generate images?
Electron microscopes generate images by passing a beam of electrons through a specimen (TEM) or by bouncing electrons off the surface of a specimen (SEM).
What are the advantages of electron microscopes over light microscopes?
Advantages of electron microscopes over light microscopes are that they:
- have higher resolving power
- can magnify objects many more times (x500 000 compared to x2000)
- can be used to show the details of internal cellular structures
How are specimens prepared using freeze fracture techniques?
A specimen is rapidly frozen
The frozen tissue is broken apart, or fractured, exposing a surface that can be viewed
For what purpose is cryogenic electron microscopy used?
Cryogenic electron microscope is used for viewing the 3D structures of, e.g.:
* proteins
* viruses
* cell membranes
How can fluorescent stains be used in microscopy?
Fluorescent stains are used in light microscopy; the dyes bind to specific target structures inside cells and then emit light when irradiated, showing where the structures are located within the cell.
What is immunofluorescence in microscopy?
Immunofluorescence uses antibodies with fluorescent dyes attached; the antibodies bind to specific target molecules and the dyes fluoresce when irradiated, showing whether or not, or where, the target molecules are present.
What is the role of cytoplasm within cells?
The role of cytoplasm within cells is to provide a medium in which the chemical reactions of cell metabolism can occur.
Which molecule makes up the genetic material of typical cells?
The genetic material of typical cells is made from DNA.
Outline the common structures to all cells.
Typical cells have DNA as genetic material and a cytoplasm composed mainly of water, which is enclosed by a plasma membrane composed of lipids.
Outline the function of structures that are common to all cells.
Plasma Membrane – All cells must have an outer border to maintain an internal chemistry that is different to the exterior (homeostasis)
Genetic Material – All cells must contain coded instructions (DNA) that function to control internal activities within a cell (metabolism)
Ribosomes – All cells must contain ribosomes in order to translate the cell’s coded instructions into functional elements (proteins)
Cytosol – All cells must contain an internal fluid that functions as a reaction medium for all necessary metabolic processes
What is the role of cytoplasm in cells?
Medium for Chemical Reactions
Cytoplasm provides the environment for the cell’s metabolism—all the chemical reactions that sustain life.
Molecular Transport
Nutrients, waste products, and signaling molecules move through the cytoplasm, ensuring that all parts of the cell are connected and functional.
Support and Shape
The cytoplasm helps maintain the cell’s shape and provides a supportive medium for organelles, preventing them from collapsing or floating aimlessly.
Why do cells need a plasma membrane?
Selective Permeability
The plasma membrane regulates what enters and exits the cell.
It allows essential nutrients like glucose to enter while keeping harmful substances out.
Compartmentalization:
By enclosing the cytoplasm, the membrane creates a distinct internal environment, enabling the cell to maintain conditions necessary for life.
Communication
Proteins in the membrane act as receptors, detecting signals from the environment and triggering responses within the cell.
Energy Processes
In some cells, like bacteria, the plasma membrane plays a role in energy production, such as generating ATP through processes like cellular respiration.
What are the roles of DNA, cytoplasm and a plasma membrane in all cells in addressing the fundamental challenges of life?
Inheritance: DNA provides a stable mechanism for storing and passing on information.
Metabolism: Cytoplasm offers a dynamic environment for the chemical reactions that sustain life.
Boundary Maintenance: The plasma membrane protects the cell and regulates its interactions with the environment.
What are the process of life that occur in unicellular organisms?
Metabolism – Living things undertake essential chemical reactions
Reproduction – Living things produce offspring, either sexually or asexually
Sensitivity – Living things are responsive to internal and external stimuli
Homeostasis – Living things maintain a stable internal environment
Excretion – Living things exhibit the removal of waste products
Nutrition – Living things exchange materials and gases with the environment
Growth / Movement – Living things can move and change shape or size
What is homeostasis?
Homeostasis is the maintenance of internal conditions within tolerable limits.
What is excretion?
Excretion is the disposal of metabolic waste products, including carbon dioxide from respiration.
Define the term metabolism.
The sum of all chemical reactions occurring in an organism to maintain life, including reactions that break down molecules for energy (catabolism) and reactions that build molecules for growth and repair (anabolism).
What is the function of mitochondria in unicellular organisms?
The function of mitochondria in unicellular organisms is to release energy for cell processes through respiration.
How are cilia and flagella involved with the life processes of unicellular organisms?
Cilia and flagella are involved with movement and responsiveness. They allow unicellular organisms to move around in response to stimuli.
