The Cell

There are three parts to Cell Theory All living things are made of cells. (Schleiden and Schwann) Cells are the basic unit of structure and function in living things. All cells come from other cells. (Virchow)

Cells are the basic unit of… Cells have two purposes – Structure: Cells make most physical parts of an organism. They give living things their shape, size, texture, etc. – Function: Cells control biological processes or “jobs.” Cells release chemical energy from food. Cells flex your muscles and cells send messages to your brain. Almost anything that your body does is because of cells.

All cells come from other cells. Cells reproduce through a complex process that splits one old cell into two or more new cells.

Unicellular vs. Multicellular – Some organisms are unicellular and other organisms are multicellular. – Multicellular organisms have cells that are specialized. Example red blood cells.

Unicellular describes organisms that are only one cell in size. That cell is all of the structure and does all of the functions. (Examples: bacteria, amoeba, paramecium and euglena). Multicellular describes organisms that are made of many cells that work together as a team for the organism. (Example: Red blood cells carry gasses and are pushed through the body by muscle cells).

Multicellular Organization Multicellular organisms have organized structures. Similar cells that work together for a specific function make tissues. Tissues working together for specific function(s) make organs.

Multicellular organization cont. Organs working together for specific functions make organ systems. Organ systems working together make the organism function.

Multicellular Organization cont. Cells  Tissues  Organs  Organ Systems  Organism Example cardiac muscle cells make cardiac muscle tissue. Cardiac muscle tissue with other tissues make the heart organ. The heart (an organ) with other organs make the cardiovascular system. The cardiovascular system with other systems make the human.

Multicellular - Specialized cells

Unicellular- Generalized Cells

The Organelles Organelle means “tiny organ.” Organelles are the organs of the cells. Each of these structures have a specific function. Therefore, organelle is to nucleus as organ is to brain.

Cell Structures on Pages 90, and 91 Be able to label the organelles on a picture or drawing. Use a post-it or something to book mark those pages.

The Cell Wall is a ridged outer layer that supports and protects a cell. Cell walls are not found around animal cells. Why not?

Cell Membrane- is the thin outside boundary of the cell. It “controls” what goes in and out. Food, water, gases and other molecules enter through the cell membrane. Wastes exit through the cell membrane. Cell membranes protect from harmful substances like the skin on your body.

Cytoplasm is a gel like fluid that fills the inside of a cell with several organelles floating in it. The cytoplasm is mostly made of water. It helps move substances to and from other organelles. Many important chemical reactions take place in the cytoplasm to help the cell function. cytoplasm

The mitochondria are organelles that break down sugar molecules (glucose) to release energy the cell can use. They are the “powerhouses” of the cell.

The chloroplasts capture energy from the sun and use it to attach molecules together to make food. Chloroplasts are green and are what makes plants green. Animal cells do not have them. Why don’t animal cells need chloroplasts?

The vacuoles- are storage bags in the cell that hold mostly water but can also hold wastes and food. They are much smaller in animal cells. Why are vacuoles larger in plant cells than in animal cells? Plant Cells Animal Cell

The nucleus is usually the largest organelle and directs cell functions. It is the “brain” of the cell where DNA is usually stored.

The nuclear envelope is the outer membrane of the nucleus which functions to protect the chromatin. Pores in the envelope let materials in and out. Nuclear Envelope

Chromatin are thin strands of DNA wrapped around special proteins called histones. During cell division the chromatin will reorganize as chromosomes. DNA Histone DNA

Chromosomes are tightly coiled strands of DNA. Chromosomes are needed during cell division so DNA can divide evenly and without being damaged. The nucleolus is a small object inside the nucleus that makes ribosomes. Chromosome

Ribosomes are very small factories that make a variety of proteins. They are found floating in the cytoplasm and attached to the endoplasmic reticulum. Ribosomes in the cytoplasm make proteins for the cell. Ribosomes attached to the ER make proteins to be used outside of the cell such as signal proteins. Ribosomes viewed with electron microscope

The endoplasmic reticulum, or ER for short, is a maze of membranes with ribosomes attached. The ER makes proteins with the ribosomes as well as some lipids. After the ER makes the proteins they are sent to the golgi bodies. Endoplasmic Reticulum under the electron microscope Endoplasmic Reticulum Animation

The golgi bodies are flattened membrane sacs that modify and package proteins from the ER to send outside of the cell through the cell membrane. Golgi Bodies

Lysosomes are containers containing chemicals that recycle used parts and organic compounds. Mitochondria Lysosome

Big Misunderstanding Not all plant and animal cells have the same type and number of organelles as the ones on 90 and 91.

Examples Egg and sperm cells have half as much chromatin/chromosomes. In addition, egg cells have very large amounts of cytoplasm where extra nutrients are stored for developing new life. More cytoplasm means bigger cell membranes. How might a muscle cell be different too?