Cells and Their Organelles Flashcards
What is the structure of the cell membrane?
The cell membrane is composed of a double layer of phospholipids, with hydrophilic phosphate head groups facing the aqueous internal and external environments and hydrophobic lipid tails oriented towards each other. Cholesterol is also present and affects the fluidity of the membrane.
What is the function of cholesterol in the cell membrane?
Cholesterol in the cell membrane helps regulate its fluidity, making it more stable and less permeable to certain molecules.
What is the role of phosphatidylcholine in the cell membrane?
Phosphatidylcholine is one of the most common lipids found in the cell membrane, contributing to its structure and stability.
What are some functions of membrane proteins?
Membrane proteins have various functions, including serving as catalysts (enzymes), transporters, pumps, ion channels, receptors for hormones, local mediators, neurotransmitters, and energy transducers.
What is the relationship between the amount of proteins and cellular activity or organelles?
Cells or organelles that are more active tend to contain more proteins. This demonstrates that the specialization of function determines the structure.
How are proteins arranged in the cell membrane?
Proteins in the cell membrane can either be integral, deeply embedded within the lipid bilayer, or peripheral, associated with the surface of the cell.
What is the nature of phospholipid molecules in the cell membrane?
Phospholipid molecules are amphipathic, meaning they have both hydrophilic (water-loving) and hydrophobic (water-repelling) properties. In water, they spontaneously form bilayers with the hydrophilic head groups facing outward and the hydrophobic tail groups facing inward.
What forces are involved in maintaining the structure of the phospholipid bilayer?
In the bilayer, van der Waals forces act between the fatty acid tails of the phospholipids, while electrostatic and hydrogen bonds form between the hydrophilic groups of the phospholipids and water. These forces help maintain the stability and integrity of the membrane structure.
What is the main function of cell membranes?
Cell membranes have multiple functions, including forming a continuous, highly selectively permeable barrier around cells and intracellular compartments.
Why is the control of the enclosed chemical environment important for cell membranes?
The control of the enclosed chemical environment by cell membranes is crucial for maintaining ion gradients, which are essential for various cellular processes.
How do cell membranes facilitate communication?
Cell membranes allow communication both with the extracellular space and within different compartments of the cell. They play a role in signal transduction and the exchange of molecules and information.
What is the significance of recognition by cell membranes?
Cell membranes are involved in recognition processes, including the recognition of signaling molecules, adhesion proteins, and other host cells. This recognition is particularly important in the immune system.
How do cell membranes contribute to signal generation?
Cell membranes can generate signals in response to a stimulus, leading to a change in membrane potential. This electrical signal can trigger various cellular responses and functions.
What is the main role of the rough endoplasmic reticulum (RER) in the cell cytoplasm?
The main role of the RER is to take developing proteins from the cytosol and continue their development prior to completion in the Golgi apparatus.
What happens to proteins that move across the membrane of the RER?
Proteins that move across the membrane of the RER undergo a series of post-translational modifications, including the addition of signal sequences that target them to the correct part of the cell.
In what cellular contexts is the rough endoplasmic reticulum (RER) abundant?
Cells that produce many secretory proteins, such as mucus and enzymes, will have extensive RER and mitochondria.
What are some destinations for proteins synthesized in the RER?
Proteins synthesized in the RER can be destined for secretion into the extracellular matrix, association with the cell membrane (such as receptors and channels), or incorporation into membrane-bound vesicles (such as enzymes of lysosomes).
What is the fate of correctly folded proteins in the endoplasmic reticulum (ER)?
Correctly folded proteins in the ER are transported to the Golgi apparatus for secretion.
What happens to incorrectly folded proteins in the endoplasmic reticulum (ER)?
Incorrectly folded proteins in the ER are retained within the cell and eventually destroyed.
What is the main function of the smooth endoplasmic reticulum (SER)?
The smooth endoplasmic reticulum is involved in the synthesis of lipids, phospholipids, and steroids. It is often less extensive and lacks ribosomes, but certain specialized tissues, such as steroidogenic cells and muscles, may have extensive SER.
What is the specialized form of smooth endoplasmic reticulum found in muscle?
The specialized form of smooth endoplasmic reticulum found in muscle is called the sarcoplasmic reticulum (SR).
What is the role of the sarcoplasmic reticulum (SR) in muscle?
The sarcoplasmic reticulum (SR) in muscle plays a major part in the sequestration of calcium ions. It modulates the tonic force of contraction and relaxation in muscle cells.
How does the ultrastructure of the sarcoplasmic reticulum differ between muscle types?
In striated muscle, the sarcoplasmic reticulum is arranged around the perpendicular T tubule, forming diads in cardiac muscle and triads in skeletal muscle. The arrangement allows for the initiation of a calcium spike in response to the action potential and surface calcium influx.
What is the main role of the Golgi apparatus?
The Golgi apparatus is responsible for modifying proteins and lipids received from the endoplasmic reticulum. It processes these biomolecules before they are delivered to various intracellular or extracellular targets.
