ملخص CELL STRUCTURE AND FUNCTION في العلوم باللغة الإنجليزية للصف السادس (2)

CELL STRUCTURE AND FUNCTION

What surrounds a cell?

Every cell is surrounded by a protective boundary called a membrane. The cell membrane is a flexible covering that protects the inside of a cell from the outside.

Cell membrane: The cell membrane surrounds the cytoplasm. The cytoplasm is a fluid inside a cell that contains salt and other molecules. The cell membrane controls the movement of substances in and out of cells. It is semipermeable (only allows certain substances to enter the cell)

Cell wall: Plant cells, fungal cells, bacteria, and some types of protists have cell walls. A cell wall is a stiff structure outside the cell membrane. It protects the cell from attacks by viruses and other harmful organisms. It helps the cell to maintain its shape and gives it structural support.

How does cell size affect the transport of materials?

Nutrients, oxygen, and other materials enter and leave a cell through the cell membrane.

Surface Area and Volume: The movement of substances in and out of the cell is important for survival. For this movement the surface area of the cell must be large compared to its volume. Area – the cell’s surface area Volume – Amount of space inside the cell. As a cell grows, both its volume and its surface area increase. The volume of a cell increases faster than its surface area. If a cell were to keep growing, it would need large amounts of nutrients and would produce large amounts of waste material. However, the surface area of the cell’s membrane would be too small to move enough nutrients and wastes through it for the cell to survive.

What organelles are involved in the transport of materials?

Ribosomes: Proteins help cells communicate with each other while others transport substances inside cells. Proteins are made on small structures called ribosomes. A ribosome is not surrounded by a membrane.

Endoplasmic Reticulum (ER): Ribosomes can be attached to a weblike organelle, the ER. The ER spreads from the nucleus throughout the cytoplasm. ER with ribosomes is called rough endoplasmic reticulum. ER without ribosomes is called smooth ER. Smooth ER removes harmful substances from the cell.

Vacuoles: Vacuoles are organelles that store food, water, and waste material. A plant cell will usually have one large vacuole. Some animal cells have many small vacuoles. Vacuoles help plants to stay rigid and supported when filled with water.

The Golgi Apparatus: Proteins are prepared for their jobs by the Golgi apparatus. It packages the proteins into tiny, membrane-bound, ball like structures called vesicles. Vesicles transport substances from area in a cell to another area in the cell. Some vesicles in animal cells are called lysosomes, they contain substances that help break down and recycle cellular components.

What powers cellular activity?

Mitochondria: It powers the cell through a chemical reaction called cellular respiration. It is found in both plant and animal cells. Cellular respiration is a series of chemical reactions that convert the energy in food molecule into a usable form of energy called ATP.

Chloroplasts: In addition to mitochondria, plant cells contain organelles called chloroplast. These organelles use light energy and make food – a sugar called glucose-from water and carbon dioxide.

What controls all these activities?

The nucleus directs all the cell activities and contains important cellular information stored in DNA. DNA is organized into structures called chromosomes. The DNA carries information that provides instructions for making all the proteins a cell requires. The nucleus contains the nucleolus. The nucleolus makes ribosomes, the organelle that helps with the production of proteins. Proteins are needed for almost every function in the body.

What is the difference between plant and animal cells?

What can different cells do? Multicellular organisms have different types of cells with different functions that enable the survival for the entire organism. The cell structure relates to what the cell does. Red blood cells are disk-shaped, which helps them move through blood vessels so they can carry oxygen.

Xylem cells are tubelike cells that can transport water from the roots to the leaves of plants.

The neuron (nerve cell) in animals transmits impulses from different parts of the body.

Summary:

Organelle Nucleus Mitochondria Chloroplast Cell wall

Cell membrane

Function Controls cell activities and contains important cellular information. Cellular respiration happens here to provide energy for the cell in the form of ATP Use light energy to make food (glucose) for plants, using water and carbon dioxide. A stiff structure outside the cell membrane. It protects a cell and helps maintain the cell’s shape and gives structural support. It surrounds the cytoplasm and protects the inside of a cell. It is semipermeable and it controls what enters or leaves the cell.

Plant, Animal, both? Both Both Plant Plant

Both