Cells

Cells ➔ The cell is the smallest unit of any living thing ➔ In 1665, Robert Hooke used an early microscope to examine a cork, a plant material ◆ He saw thousands of tiny chambers, which he called “cells” ➔ Three main discoveries were confirmed by many biologists and established in the cell theory ➔ Cell Theory ◆ All living organisms are made of one or more cells ◆ The cell is the fundamental living unit; it is the unit of structure and function in living things ◆ New cells arise from preexisting cells ➔ Cells fall into two broad categories: Prokaryotes and Eukaryotes ◆ A cell that contains a nucleus is eukaryotic ◆ A cell that does not contain a nucleus is prokaryotic ● The nucleus contains the cell's genetic material (DNA) ○ It is large and enclosed by a membrane ◆ Generally, eukaryotic cells are larger and more complex than prokaryotes ◆ Plants, animals, and fungi are eukaryotes, meaning they have nuclei ➔ Cell Structure ◆ The cytoplasm is the liquid portion of the cell outside the nucleus ◆ The cell organelles are located inside the cytoplasm ● An organelle is a cellular structure with a specific function and role ◆ A cell can be compared to a factory since both have many structures that each play different roles to collectively make the entire system function properly ◆ The nucleus contains almost all of the cell’s DNA, which codes for making molecules needed for the cell such as proteins ● Since prokaryotic cells do not have nuclei, the DNA is circular and found in the cytoplasm ◆ The nucleus is composed of two membranes, and it has many pores to allow materials to enter and exit ● Molecules move into and out of the nucleus ◆ Most nuclei contain a dense region called the nucleolus ◆ The membrane surrounding the nucleus is called the nuclear membrane ◆ Ribosomes assemble proteins in the cell (protein synthesis) ● To do this, they must follow the code in DNA ◆ Endoplasmic Reticulum (ER) ● The Rough ER has ribosomes on its surface, allowing for the synthesis of proteins ● Newly made proteins leave ribosomes and enter the ER ● The Smooth ER does not have ribosomes on its surface ○ It synthesizes (makes) lipids and detoxifies drugs ◆ Proteins assembled in the Rough ER then enter the Golgi apparatus (Golgi complex) ● The Golgi apparatus modifies, sorts, and packages proteins and other molecules ● The packaged items will either be kept in the cell or shipped out of it ○ Proteins are shipped to their final destination ◆ Another important organelle is the vacuole, a large sac-like structure ● Vacuoles store water, wastes, food (carbohydrates), proteins, and other materials ○ Many plant cells have one large central vacuole, while animal cells have much smaller vacuoles ● Lysosomes are the cleaning crew of the cell ○ Think “Lysol” for “lysosome” since Lysol is a cleaning agent ○ Lysosomes break down wastes and foods like carbohydrates ○ They also break down organelles that do not work anymore ◆ Additionally, the cytoskeleton consists of protein filaments that help give the cell its shape and are involved in cellular movement ● The filaments are located in the cytoplasm of the cell ◆ The mitochondria are the powerhouses of the cell ● They convert the chemical energy in food into ATP energy (which is energy that the cell likes to use) ● Thus, the mitochondria are responsible for creating energy to fuel cell processes ◆ The chloroplast is in organelle only in plant cells (not animal cells) ● This organelle takes sunlight energy and converts it to chemical energy ● This is the process of photosynthesis (converting sunlight energy into food) ● Chloroplasts are comparable to solar power plants ● They also contain green pigments called chlorophyll, which is why plants are green ◆ The cell membrane is a biological membrane that separates the cell from its outside environment ● It surrounds the entire cell and also transports materials inside and outside of the cell ◆ Another organelle that is only found in plant cells is the cell wall ● The cell wall is rigid and surrounds the cell membrane ● It is strong and supports/shapes the cell by providing strength ● The cell wall is the reason why plants are strong and rigid