Grade 8 Cells And Systems Quiz

Mitochondria are known as the powerhouses of the cell because their main function is to generate energy in the form of ATP through cellular respiration. This process occurs in the inner membrane of the mitochondria, where electrons from food molecules are transferred through a series of reactions, ultimately producing ATP. Therefore, the correct answer is “converts food energy to ATP energy for the cell."

While the nucleus controls many activities in the cell by regulating gene expression, it does not control all activities. Other organelles like mitochondria and ribosomes have important roles. The other statements are true: bacteria lack a nucleus, DNA is housed in the nucleus, and the nuclear membrane is continuous with the endoplasmic reticulum.

The cell wall is not present in an animal cell. While both plant and fungal cells have a rigid cell wall made of cellulose, animal cells lack this structure. Animal cells are surrounded by a flexible plasma membrane that allows for movement and flexibility. The absence of a cell wall in animal cells enables them to change shape and move more freely compared to plant cells.

Blinking when a bright light is shone on your face is an example of a response to a stimulus because it is an automatic reflex action that occurs in response to the stimulation of the optic nerves by the sudden increase in light intensity. This reflex helps protect the eyes from potential damage caused by excessive light.

An organism that is unicellular means that it is composed of only one cell. This type of organism is simple in structure and function, as all of its life processes occur within a single cell. Examples of unicellular organisms include bacteria, archaea, and some types of algae. They are capable of performing all necessary functions for survival, such as obtaining nutrients, reproducing, and responding to their environment, within their single cell.

The correct answer is "Prokaryotic cells." Bacteria are prokaryotic cells because they lack a nucleus and other membrane-bound organelles. Prokaryotic cells are generally smaller and simpler in structure compared to eukaryotic cells, which have a true nucleus and other membrane-bound organelles. Bacteria can have various shapes, including sphere-shaped (cocci), spiral-shaped (spirilla), and rod-shaped (bacilli), but their cell type remains prokaryotic regardless of their shape.

The mitochondria are known as the "powerhouses" of the cell because they generate ATP (adenosine triphosphate), the cell's main energy currency, through cellular respiration. This process occurs in both plant and animal cells. Ribosomes synthesize proteins, the nucleus controls cellular activities by housing DNA, and lysosomes break down waste, but it is the mitochondria that are crucial for energy production in eukaryotic cells, making them essential for cell survival and function.

Cells extract energy from their food through cellular respiration. This process involves breaking down glucose molecules in the presence of oxygen to produce ATP, which is the main energy currency of cells. Cellular respiration occurs in the mitochondria of eukaryotic cells and involves a series of enzymatic reactions that release energy stored in the chemical bonds of glucose. Chlorophyll and photosynthesis are related to the process of converting sunlight into chemical energy in plants, while osmosis is the movement of water across a semipermeable membrane and is not directly involved in energy extraction.

A prokaryotic cell is a cell in which there are very few organelles, and those organelles are not enclosed in a membrane. Prokaryotic cells are typically found in bacteria and archaea, and they lack a nucleus and other membrane-bound organelles found in eukaryotic cells. This type of cell is characterized by its simplicity and smaller size compared to eukaryotic cells.

The diffusion of water particles through a selectively permeable membrane is called "osmosis." Osmosis is a specific type of diffusion that involves the movement of water molecules across a membrane from an area of lower solute concentration to an area of higher solute concentration, or vice versa, in an attempt to equalize the concentration on both sides of the membrane. This process is essential for many biological and cellular functions.