Cells (Form and Function) Flashcards
Cells have many different shapes and functions; however, what are some similarities between them (think of the modern cell theory)?
All cells form from preexisting living cells. Cells are the smallest/simplest structural and functional unit of life. Organisms are made of cells; the activities of cells are ultimately responsible for the organisms form and function.
Describe the difference between microvilli and cilia in terms of form and function.
Microvilli are finger like proteins filaments that project from the outer lipid layer of the plasma membrane. They increase surface area of the plasma membrane to help in the absorption of substances. They move in an “up-and-down” milking like motion pushing contents into the cell.
Cilia are hair like projections on the outer lipid layer border of the plasma membrane. They move in sequential waves (power strokes followed by recovery strokes) to move mucus and foreign particles along the cell surface. These can be found in the nasal cavity, inner ear, etc. to trap foreign particles and move them out.
Plasma membranes act to protect the internal environment of a cell from the external environment of the cell. However, there are times that contents need to move across the membrane to maintain homeostasis. Describe the difference between active and passive transport of contents across the membrane.
Active transport requires ATP (energy molecule) to move contents against their concentration gradient. Passive transport does not require energy (no ATP needed). This movement of contents happens down a concentration gradient (from an area of higher concentration to an area of lesser concentration).
Describe how filtration (an example of active transport) moves contents through a selectively permeable membrane.
Filtration relies on hydrostatic pressure to move contents across a membrane. Hydrostatic pressure is the force that is exerted on a membrane by water. When hydrostatic pressure is high (higher pressure on one side of the membrane versus the other), water forces its way through the membrane carrying contents (nutrients or wastes) with it. Remember that membranes are selectively permeable; therefore, only those particles that are small enough to “fit” through the membrane will move with the water.
Diffusion is a passive means by which particles can move across a membrane; specifically from an area of high concentration to low concentration. What factors can effect diffusion rates?
- Temperature: increases motion of particles
- Molecular weight: larger molecules move slower
- Steepness of concentration gradient: higher gradient leads to a higher rate
- Membrane surface area: the larger the area, the higher the rate
- Membrane permeability: the more permeable the membrane, the higher the rate
Describe the difference between a hypertonic solution and a hypotonic solution.
Tonicity refers to the amount of solute in fluid. In humans, this fluid is water and the solute can be a molecule, element, etc. A hypertonic solution is a solution that has a higher concentration of solute versus water. A hypotonic solution is a solution that has a lower concentration of solute versus water. If a solution is hypertonic, it has more solute outside of the cell, which causes the cell to crenate (shrivel); this is due to water being pulled out of the cell in an attempt to equalize hydrostatic pressure on each side of the cell. In doing so, too much water has to be “pulled” from the cell to the extracellular space causing the cell to crenate. The opposite is true with a hypotonic solution. A cell that is living in a hypotonic solution is faced with having more water outside the cell (extracellular space); a cell wants to maintain homeostasis on both sides of its membrane. With more water volume outside the cell, the cell will pull water into itself to equalize hydrostatic pressure. In doing so, it pulls more water inward causing the cell to swell (it can swell to the point that the cell breaks).
Explain carrier mediated transport and the two different types
Carrier mediated transport is a means by which solutes can move across a cell membrane. This process requires a protein carrier that has a receptor responsible for detecting and carrying a specific solute (this is referred to as specificity). There are 2 types of carrier mediated transport:
- Facilitated diffusion - passive transport of a solute across the cellular membrane down its concentration gradient.
- Active transport - transport of a solute against its concentration gradient (e.g., sodium-potassium pump).
Explain vesicular transport and the difference between phagocytosis and pinocytosis.
Vesicular transport is movement of a substance through a cell membrane through a bubble-like vessel.
- Phagocytosis is the process in which the cell engulfs particles so they can be moved away from tissue
- Pinocytosis is also referred to as cell-drinking. This process relies on the cell pulling in droplets of extracellular fluid into the cytoplasm. These droplets encapsulate foreign substances and carry them across the cell membrane.
Describe the function of the nucleus within a cell.
The nucleus is the largest organelle of a cell and is located within the cytoplasm. Not all cells have a nucleus and some cells may have several nuclei. Its function is to contain DNA (which is produced in the nucleoli).
The nucleus also houses the nucleoli, which is also responsible for making ribosomes. Once the ribosomes are produced, the nucleus is responsible for moving them out to the cytoplasm where they attach to the endoplasmic reticulum.
Describe the difference (anatomically and physiologically) between the rough endoplasmic reticulum and smooth endoplasmic reticulum.
The rough endoplasmic reticulum is characterized by small dark protein granules (called ribosomes) attached to the surface. While both the rough and smooth endoplasmic reticulum are situated close to the nucleus, the smooth endoplasmic reticulum is an extension of the rough endoplasmic reticulum and does not contain ribosomes.
The function of the rough endoplasmic reticulum is to synthesize protein and to produce cellular membranes. The function of the smooth endoplasmic reticulum is to synthesize fat, store calcium, and assist in cellular detoxification.
What is the function of ribosomes?
Ribosomes are protein granules located on rough endoplasmic reticulum and interpret genetic coding.
Where is ATP synthesized (within the cell)?
ATP is synthesized in the mitochondria (also known as the power house of the cell).
