Final answer:
The answer to "A soft flexible layer" in a cell context is the membrane. This cell membrane is fluid and flexible, made of a lipid bilayer with proteins and cholesterol, allowing substances to pass in and out while also enabling cells to maintain their shape and interact with their environment. Therefore correct option is A
Step-by-step explanation:
The question: "A soft flexible layer" refers to a component of the cell that characterizes its flexible nature. Considering the options provided (membrane, nucleus, organelles, contract), the correct answer is a) membrane. The cell membrane, also known as the plasma membrane, acts as a barrier that separates the inside of the cell from the external environment. It consists of a lipid bilayer that includes various proteins and cholesterol, making it fluid and flexible. This fluidity is crucial for the membrane's function, allowing it to maintain the cell's structural integrity while facilitating the movement and organization of membrane proteins.
The flexibility of the membrane and its semi-permeable nature enable it to control the passage of substances into and out of the cell, thus playing a critical role in cell homeostasis. Its fluidic character is sometimes referred to as a 'liquid crystal' due to its ability to be partially rigid for organized functioning, while also maintaining capacity for shape change and lateral movement of components. This balance h_inges on temperature, which can affect membrane fluidity.
One of the physical properties that give the cell membrane its flexibility is its coupling to the actin cortex, a network of actin filaments beneath the plasma membrane. Moreover, the cell membrane is also involved in cell signaling and interaction with the surrounding environment through embedded proteins that can transmit signals into the cell.