7th Grade Science Chap 3 Test

The cell membrane is a phospholipid layer that surrounds the cell and acts as a protective barrier. It controls the movement of substances in and out of the cell, allowing nutrients to enter and waste products to exit. This selective permeability is crucial for maintaining homeostasis and ensuring the cell's survival.

The cell wall is a structure made up of cellulose that surrounds the cell membrane of plant cells. It provides strength and support to the cell, giving it a rigid structure. The cell wall is responsible for maintaining the shape of the cell and protecting it from external forces. It also allows for the passage of water, nutrients, and other substances in and out of the cell.

Chloroplasts are organelles found in plant cells that contain chlorophyll, a pigment responsible for capturing sunlight energy during photosynthesis. This energy is then used to convert carbon dioxide and water into glucose (food) and oxygen. The chlorophyll in chloroplasts gives them a green color, as it absorbs all colors of light except for green, which is reflected back. Therefore, chloroplasts make food using the energy of the sun, and their green color is a result of the chlorophyll present.

The nucleus is the largest organelle in the cell. It contains the cell's genetic material, including DNA, which controls the cell's activities. The nucleus is surrounded by a nuclear membrane that separates it from the rest of the cell. It plays a crucial role in regulating gene expression and protein synthesis. The nucleus also contains a dense structure called the nucleolus, which is involved in the production of ribosomes. Overall, the nucleus is essential for the cell's overall function and is often referred to as the "control center" of the cell.

Mitochondria are responsible for breaking down food molecules to produce ATP, which is the energy currency of the cell. They are double-membraned organelles found in most eukaryotic cells, and they play a crucial role in cellular respiration. Through a series of biochemical reactions, mitochondria convert the energy stored in food molecules into ATP, which can be used by the cell for various metabolic processes. This process occurs in the inner membrane of the mitochondria, where enzymes and electron transport chains are located. Therefore, mitochondria are the correct answer for this question.

The vacuole is a membrane-bound organelle found in the cells of plants and some other organisms. It serves as a storage compartment for various substances, including water. The vacuole can occupy a significant portion of the cell's volume and helps maintain the cell's shape and turgor pressure. Additionally, it plays a role in storing nutrients, waste products, and pigments. Therefore, the vacuole is responsible for storing water and other liquids in the cell.

The Golgi complex is responsible for processing, packaging, and transporting materials out of the cell. It receives proteins and lipids from the endoplasmic reticulum and modifies them, adding sugars and other molecules to create functional molecules. It then packages these molecules into vesicles, which can be transported to the cell membrane for secretion or to other parts of the cell for specific functions. Therefore, the Golgi complex plays a crucial role in the export of materials from the cell.

Organelles are small structures found within cells that perform specific functions necessary for the cell to live, grow, and reproduce. These structures are like tiny organs within the cell, each with its own specialized task. Examples of organelles include the nucleus, mitochondria, endoplasmic reticulum, and Golgi apparatus. These organelles work together to carry out essential processes such as DNA replication, energy production, protein synthesis, and cell division. Without organelles, cells would not be able to function properly and would not be able to carry out the necessary processes for survival and reproduction.

The ribosome is the smallest and most abundant organelle in any cell. It is responsible for protein synthesis, where amino acids are hooked together to form proteins. Ribosomes can be found in both prokaryotic and eukaryotic cells, and they are composed of RNA and proteins. They can be free-floating in the cytoplasm or attached to the endoplasmic reticulum. Ribosomes play a crucial role in the growth, development, and functioning of cells, making them an essential organelle in all living organisms.

Lysosomes are organelles found in cells that contain enzymes responsible for breaking down various substances such as food particles, cellular waste, old cell parts, and even foreign invaders like bacteria or viruses. These enzymes help in the process of digestion and recycling within the cell. Lysosomes play a crucial role in maintaining the overall health and functionality of the cell by removing unwanted materials and aiding in the breakdown of substances for energy or elimination.

DNA is the hereditary material found in the nucleus of the cell. It carries the genetic instructions that determine the traits and characteristics of an organism. DNA is passed down from parents to offspring, making it responsible for heredity. It contains the information needed for the development and functioning of living organisms.

The endoplasmic reticulum is responsible for synthesizing lipids, as well as breaking down drugs and other chemicals, and packaging proteins for release from the cell. Lipids are a type of organic molecule that includes fats, oils, and cholesterol. They are essential for various cellular functions, such as providing energy, forming cell membranes, and acting as signaling molecules. Therefore, the endoplasmic reticulum plays a crucial role in lipid metabolism and maintaining the overall cellular homeostasis.

Robert Hooke is the correct answer because he was the first person to observe and name dead cells in cork. In 1665, Hooke used a microscope to examine a thin slice of cork and observed small, box-like structures that he called "cells" due to their resemblance to the cells of a monastery. This discovery was significant as it laid the foundation for the study of cells and cell theory.

Rudolph Virchow is the correct answer because he proposed the concept of "omnis cellula e cellula," which means that all living cells arise from pre-existing cells. This theory contradicted the prevailing belief at the time that cells could spontaneously generate. Virchow's work was instrumental in establishing the cell theory and revolutionizing the field of biology.

Theodor Schwann is the correct answer because he was a German physiologist who played a significant role in the development of cell theory. He stated that the cell is the basic unit of structure in animals, along with Matthias Schleiden who stated the same for plants. Schwann's observations and experiments with animal tissues led to the conclusion that cells are the fundamental building blocks of animal bodies. This discovery revolutionized the understanding of biology and laid the foundation for modern cell biology.

Anton van Leeuwenhoek is the correct answer because he was the first to observe and describe microorganisms, including bacteria and yeast, using a simple microscope. He also made significant contributions to the field of microbiology by documenting his observations of blood cells. Therefore, his work in studying unicellular organisms and blood cells aligns with the given information.

Matthias Schleiden is the correct answer because he was a German botanist who proposed the cell theory in 1838. He stated that all plants are made up of cells, which laid the foundation for our understanding of the cellular structure of plants. This theory was later expanded upon by Theodor Schwann, who added that all animals are also made up of cells. Together, their work contributed significantly to the development of cell biology.