24 Questions
What is the function of cell organelles in a cell?
To perform specific functions within the cell
What is the basic unit of life that consists of organelles?
Cell
What is the process by which substances move across the cell membrane?
Diffusion
Why do substances move from a region of high concentration to a region of low concentration?
By spontaneous movement
What is the term used to describe the cell membrane's ability to control what enters and leaves the cell?
Selective permeability
What happens to the substance when it accumulates in high concentrations inside the cell?
It diffuses out of the cell
What is the term used to describe the organization of cells into different components, each with a specific function?
Division of labour
What is the function of all cells, regardless of their function or organism they are found in?
To have the same organelles
What is the primary function of the cell membrane's flexibility?
To engulf food and other material from the environment
What is the direction of water movement during osmosis in a hypotonic environment?
Into the cell from the external environment
Why do plant, fungi, and bacterial cells not burst in hypotonic media?
Their cell walls exert a counter-pressure
What is the process by which Amoeba acquires its food?
Endocytosis
What is the term for the movement of water into a cell through a selectively permeable membrane?
Osmosis
What is the function of the electron microscope in understanding the structure of the plasma membrane?
To study the structure of the plasma membrane
What is the result of osmosis in a cell placed in a hypotonic environment?
The cell will swell
What is the direction of water movement in a living cell, compared to a dead cell?
Only living cells absorb water by osmosis
Who discovered the nucleus in the cell?
Robert Brown
What is the term coined by Purkinje in 1839?
Protoplasm
Who are the two biologists who presented the cell theory?
Schleiden and Schwann
What was observed by Leeuwenhoek in 1674?
Free living cells in pond water
What was made possible by the discovery of the electron microscope in 1940?
Observing the complex structure of the cell and its organelles
Who expanded the cell theory by suggesting that all cells arise from pre-existing cells?
Virchow
What is depicted in the picture shown?
Different types of cells from the human body
What was observed by Robert Hooke with the help of a primitive microscope?
Cells in a cork slice
Study Notes
Cell Structure and Function
- The cell membrane is selectively permeable, allowing certain substances to pass through while restricting others.
- The cell membrane allows substances like carbon dioxide and oxygen to move across it through diffusion.
- Water can cross the cell membrane in both directions, but in a process called osmosis, more water leaves the cell than enters it, causing the cell to shrink.
Cellular Organelles and Division of Labour
- Each cell has specific components called organelles, which perform special functions.
- Examples of organelles include ones that make new material, clear waste, and perform other functions.
- All cells have the same organelles, regardless of their function or the organism they are found in.
Cell Membrane Flexibility
- The flexibility of the cell membrane enables the cell to engulf food and other materials from its external environment through a process called endocytosis.
- Amoeba acquires its food through endocytosis.
Osmosis and Cell Size
- Osmosis is a special case of diffusion through a selectively permeable membrane.
- Living cells can absorb water by osmosis, but dead cells cannot.
- Cell walls in plants, fungi, and bacteria allow cells to withstand very dilute external media without bursting.
Cell Discovery and Theory
- Antonie van Leeuwenhoek discovered free living cells in pond water in 1674 using a primitive microscope.
- Robert Brown discovered the nucleus in 1831.
- The cell theory, which states that all plants and animals are composed of cells and that the cell is the basic unit of life, was presented by Schleiden (1838) and Schwann (1839).
- The cell theory was further expanded by Virchow (1855) by suggesting that all cells arise from pre-existing cells.
Electron Microscope and Cell Structure
- The discovery of the electron microscope in 1940 allowed for the observation and understanding of the complex structure of the cell and its various organelles.
- The structure of the plasma membrane can only be observed through an electron microscope.
Learn about the cell membrane's selective permeability, how substances pass through it, and the role of osmosis in cell function.
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