The World of Cells

Cell Theory In 1665, Robert Hooke, using a microscope that he made, was the first scientist to observes cells. After many years of scientists observing cells, the cell theory was developed.

Cell Theory (continued) There are three main ideas of the cell theory. They are: 1) All living things are made of one or more cells. 2) The cell is the basic unit of life in which the activities of life occur. 3) All cells come from cells that already exist.

Parts of Animal and Plant Cells

Cell Membrane is a flexible structure that holds the cell together. forms a boundary between the cell and its environment. helps control what enters and leaves the cell.

CELL MEMBRANE

Cytoplasm is a gelatinlike substance that fills the inside of the cell. mostly consists of water, but also contains chemicals that are needed by the cell. is where the cell’s activities take place.

The clear areas are the cytoplasm in these human eye cells.

Organelles are specialized cell parts that move around in the cytoplasm. perform cellular activities that are necessary for life. are found in all cells, except bacterial cells.

Nucleus directs and controls most of the cell’s activities. has chromosomes inside of it, which contain all the hereditary material for the organism.

cell nucleus magnified 450X Onion cell nucleus magnified 450X

Inside the Nucleus Chromosomes DNA is found inside chromosomes. It determines which traits an organism will have, such as the color of your eyes or whether you will be short or tall.

Vacuoles are balloonlike organelles in the cytoplasm. store food, water, and other substances until the cell is ready to use it. can also store waste until the cell is ready to get rid of it.

The vacuole in this plant cell is so large that it has pushed the chloroplasts, nucleus, and other organelles up against the cell membrane.

Mitochondria provide energy for the cell. performs the process of cellular respiration—a series of chemical reactions in which energy stored in food is converted to a form of energy that the cell can use.

Six mitochondria can be seen in this brain cell of a rat.

There are 2 structures plant cells have that animal cells do not There are 2 structures plant cells have that animal cells do not. CAN YOU NAME THEM?

Cell Wall is found outside of the cell membrane. provides support and protection for the cell.

Chloroplasts capture light energy and combine carbon dioxide from the air with water to make food—also known as the process of photosynthesis. contain green pigment which gives many leaves and plants their green color.

CELL WALL CHLOROPLASTS

The Different Jobs of Cells

Cells that make up many-celled organisms are specialized Cells that make up many-celled organisms are specialized. Different kinds of specialized cells work as a team to perform the life activities of a many-celled organisms.

Different Types of Plant Cells 1) Cells found in the stems of plants are long and tube-shaped. They move water and other materials up through the plant. 2) Leaf cells are brick-shaped and contain many chloroplasts. 3) Root cells are block-shaped and do not contain chloroplasts.

Different Types of Human Cells 1) Skin cells are mostly flat and close together to form a protective layer for our bodies. 2) Muscle cells are long and have many fibers that can contract and relax. These cells usually have many mitochondria in them because muscle cells need a lot of energy. 3) Blood cells are disk-shaped so they can move easily through veins, arteries, blood vessels, and capillaries. They deliver oxygen to the tissues and organs in your body.

Different Types of Human Cells (continued) 5) Fat cells can store so much fat that the nucleus and other organelles get pushed against the cell membrane. 6) Nerve cells are long and have many branches. This allows them to receive and deliver messages quickly. 4) Bone cells are surrounded by a hard substance made of calcium and phosphorous.

Cell Organization Cells are organized into systems that, together, perform functions that keep the organism healthy and alive. Cell organization, from smallest to largest, is as follows: Cell-smallest unit of an organism that can carry on life functions Tissue-group of similar cells that all do the same sort of work Organ-structure made of two or more different tissue types that work together to do a certain job Organ System-group of organs that work together to perform a certain job Organism-any living things that are made up of cells, use energy, reproduce, respond, and grow and develop

rat circulatory system rat heart cells rat heart tissue rat heart Cell Organization = rat circulatory system rat