24 Questions
What is a characteristic of phospholipid molecules that make up cell membranes?
They have both hydrophobic and hydrophilic ends
What is the primary function of the cell membrane?
To regulate the flow of materials into and out of the cell
What type of diffusion involves the movement of molecules down a concentration gradient without the use of cellular energy?
Passive diffusion
What is the term for the passive diffusion of water molecules across a membrane in response to a concentration gradient of solute?
Osmosis
What is the function of permease in facilitated diffusion?
To assist the movement of molecules across the membrane
What is the term for the movement of molecules from regions of higher to lower concentrations?
Diffusion
What is the structure formed by the arrangement of phospholipid molecules in a cell membrane?
A phospholipid bilayer
What is the result of a cell being placed in a hypertonic environment?
The cell will shrink
What is the primary function of the cytoplasmic membrane in a prokaryotic cell?
To control the movement of substances in and out of the cell
What is a characteristic of the cytoplasmic membrane?
It is selectively permeable to ions and organic molecules
What is a function of the cell membrane in cellular processes?
Cell adhesion and signaling
What is the role of the cytoplasmic membrane in protecting the cell?
It protects the cell from outside forces
What is the function of phospholipid molecules in the cell membrane?
To form the phospholipid bilayer
What is a characteristic of cell signaling that involves the cell membrane?
It is a process of cell-to-cell communication
What is the relationship between the cell membrane and the cell wall?
The cell membrane is attached to the cell wall
What is a function of the cytoplasmic membrane in relation to the extracellular structures?
It serves as an attachment surface for extracellular structures
What type of transport moves substances across the membrane from an area of low concentration to an area of high concentration?
Active transport
What is the primary function of the cell wall in bacteria?
To provide structural support and maintain cell shape
Which type of transport involves the movement of molecules down their concentration gradient?
Passive transport
What is the result of the Gram stain on Gram-positive bacteria?
The cell wall appears thick and single-layered
What is the purpose of the phosphotransferase system in group translocation?
To metabolize the molecule during transport
What is the main function of the cytoplasmic membrane?
To regulate the transport of molecules across the membrane
What is the purpose of the cell wall in protecting the cell against osmotic shock?
To prevent the cell from shrinking or bursting
What type of molecules can move through the cell wall?
Small molecules only
Study Notes
Cell Membrane Structure
- Composed of phospholipid molecules with polar (hydrophilic) and non-polar (hydrophobic) ends
- Two layers of phospholipids, with internal matrix (hydrophobic ends) and one hydrophilic end pointing away from the cell and the other pointing towards the cell's cytoplasm
Cell Membrane Functions
- Primary function: regulation of flow of material into and out of the cell
- Diffusion:
- Characteristics: movement of molecules from regions of higher to lower concentrations (down a concentration gradient)
- No energy is expended by the cell to assist the molecules as they diffuse across the cytoplasmic membrane
- Cytoplasmic membrane restricts free diffusion of macromolecules
- Types of diffusion:
- Passive diffusion: diffusion of solutes across a membrane without the use of cellular energy
- Osmosis: the passive diffusion of water molecules across a membrane in response to a concentration gradient of solute
- Facilitated diffusion: involves a carrier protein called a permease
Cell Division and Reproduction
- Bacterial cell division: 2 daughter cells may or may not remain close to one another, forming cell aggregates characteristic of the species
- Cocci may divide in one plane only, forming pairs of bacteria (diplococci) or chains of cells (streptococci)
Nomenclature of Bacteria
- Bacteria are given binomial Latin-ending names designating the genus and species
- Genus name must be capitalized, while species name is generally not
- Many bacteria have common names, e.g. Mycobacterium tuberculosis is known as the tubercle bacillus or simply TB
Cell Structure and Function
- Cytoplasmic membrane is the dividing boundary layer of the cell
- Functions:
- Separates the interior of all cells from the outside environment
- Is selectively permeable to ions and organic molecules
- Controls movement of substances in and out of cells
- Protects the cell from outside forces
- Involved in cell adhesion, ion conductivity, cell signaling, and serves as the attachment surface for extracellular structures
Cell Membrane Transport
- Passive transport: movement of molecules down a concentration gradient without the use of cellular energy
- Active transport:
- Protein carrier moves substance across the membrane
- Movement is against a concentration gradient (up the concentration gradient)
- Energy is supplied by ATP or chemiosmosis
- Group translocation: a type of active transport found in prokaryotic cells, where the molecule is metabolized as it is transported across the cytoplasmic membrane
Cell Wall Structure
- Bacteria can be divided into two major groups: Gram-positive and Gram-negative
- Gram-positive and Gram-negative cells differ in the appearance of their cell walls
- Gram-negative cell wall is a multilayered structure, while Gram-positive cell wall consists of primarily a single type of molecule and is often much thicker
- Cell wall functions:
- Surrounds the cytoplasmic membrane of most prokaryotic cells and eukaryotic microorganisms
- Is relatively porous, allowing small molecules to move to and from the cytoplasmic membrane
- Is relatively rigid, giving bacteria their shape
- Protects the cell against osmotic shock
Explore the composition and arrangement of phospholipid molecules in the cell membrane, and learn about the primary functions of the cell membrane in regulating the flow of materials.
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