Cell Unit Notes: Organelles and Their Functions

1. Cell Unit Notes:Organelles and Their Functions

2. Cell Theory The Cell Theory has 3 parts: • 1) All organisms are made up of one or more cells and the things produced by cells. • 2) Cells are the basic structural and functional component of all living things; cells carry out the activities necessary to keep an organism alive (like produce energy from carbohydrates • 3) New cells arise only from other living cells by the process of mitosis.

3. The Four Main Components 1. PLASMA MEMBRANE/ CELL MEMBRANE • Structure- a phospholipid bi-layer composed of proteins and carbohydrates. It is called “fluid” because it’s not a rigid, hard structure. It flexes and moves with the organism. • Function - the cell membrane separates the cell from its external environment, and is selectively permeable (controls what gets in and out). It protects the cell and provides stability.

4. The Four Main Components 1. Cell membrane, continued…. • Proteins are found embedded within the plasma membrane, with some extending all the way through in order to transport materials into and out of the cell. • Carbohydrates are attached to proteins and lipids on the outer lipid layer. The carbohydrates function as chemical identification tags.

5. The Four Main Components 2. CYTOPLASM • Structure - The jelly-like substance composed of mainly water and found between the cell membrane and nucleus. The cytoplasm makes up most of the "body" of a cell and is constantly streaming. • Function - Organelles are found here and substances like salts may be dissolved in the cytoplasm.

6. The Four Main Components 3. NUCLEUS • Structure – the control center of the cell. It is dark and round, and is surrounded by a double membrane called the nuclear envelope/membrane. The nucleus contains genetic information (DNA) on special strands called chromosomes. Chromatin is what it’s called when chromosomes are bound to proteins. Your DNA usually exists as chromatin in your cells; it only coils up into visible chromosomes during mitosis.

7. The Four Main Components 3. NUCLEUS, continued…. • Nuclear pores dot the nuclear membrane (also called the nuclear envelope) and allow materials to move into and out of the nucleus • The nucleolus is a dark spot inside the nucleus where ribosomes are made.

8. The Four Main Components 4. CYTOSKELETON • The cytoskeleton is a network of protein filaments that help the cell maintain its shape and form pathways to help move substances and structures around in the cell. • The cytoskeleton is made of 3 main components, listed from largest to smallest: • Microtubules—largest component of the cytoskeleton; structure = hollow tube of protein; function = serve as “tracks” to move organelles around the cell AND pull chromosomes apart during anaphase of mitosis. Cilia and flagella are made of microtubules.

9. The Four Main Components 4. CYTOSKELETON • Intermediate filaments—medium size cytoskeletal element; function = help stabilize the nuclear membrane • Microfilaments—sometimes called actin filaments; smallest component of the cytoskeleton; structure = long, thin fibers like hairs; function = form a band of support directly inside the cell membrane and link proteins in the cell membrane to the cytoplasm.

10. FOUND IN both PLANT AND ANIMAL CELLS 1. "ER" OR ENDOPLASMIC RETICULUM • The Endoplasmic Reticulum is a network of membranous sacs in which the components of the cell membrane are manufactured AND in which some proteins are completed or modified. • There are two types of ER: rough ER and smooth ER.

11. FOUND IN both PLANT AND ANIMAL CELLS 1. "ER" OR ENDOPLASMIC RETICULUM • Rough Endoplasmic Reticulum is lined with ribosomes and it looks “bumpy” or “rough” because of the ribosomes that dot its surface. Proteins that are to be released from the cell are completed and modified inside the rough ER. • Smooth endoplasmic reticulum contains no ribosomes and is smooth in appearance. The components of the cell membrane are made in the smooth ER.

12. FOUND IN both PLANT AND ANIMAL CELLS 2. RIBOSOMES • Ribosomes are small particles which are found individually in the cytoplasm and also line the membranes of the rough endoplasmic reticulum. • Ribosomes make proteins.

13. FOUND IN both PLANT AND ANIMAL CELLS 2. RIBOSOMES, continued…. • Ribosomes can be found dotting the surface of the rough ER and sometimes on the nuclear membrane. • Ribosomes can also be found floating free in the cytoplasm. These “free” ribosomes make proteins that will be used by the cell itself.

14. FOUND IN both PLANT AND ANIMAL CELLS 3. GOLGI BODY / APPARATUS • Golgi bodies are stacks of flattened membranous stacks (they look like pancakes!). • The Golgi Body temporarily stores protein which can then leave the cell via vesicles pinching off from the Golgi. • The Golgi body receives proteins in vesicles from the rough ER. Enzymes in the Golgi body modify the proteins by adding carbohydrate and lipids. Then, the Golgi packages the proteins inside a new vesicle and sends them where they need to go.

15. FOUND IN both PLANT AND ANIMAL CELLS 4. LYSOSOMES • Lysosomes are small sac-like structures surrounded by a single membrane and containing strong digestive enzymes which when released can break down worn out organelles or food. • The lysosome is also known as a suicide sac.

16. FOUND IN both PLANT AND ANIMAL CELLS 5. MITOCHONDRIA • The mitochondria are round "tube-like" organelles that are surrounded by a double membrane, with the inner membrane being highly folded. • the mitochondria are often referred to as the "powerhouse" of the cell. • the mitochondria releases food energy from food molecules to be used by the cell. This process is called respiration. • Some cells( muscle cells) require more energy than other cells and so would have many more mitochondria.

17. FOUND IN both PLANT AND ANIMAL CELLS 6. VACUOLES • Vacuoles are fluid filled organelles enclosed by a membrane. • They can store materials such as food, water, sugar, minerals and waste products.

18. ORGANELLES NOT FOUND IN PLANT CELLS 1. CILIA AND FLAGELLA • Both cilia and flagella are hair-like organelles which extend from the surface of many animal cells. • Both are made of elements of the cytoskeleton, except that flagella are longer and whip-like and cilia are shorter. • There are usually only a few flagella on a cell, while cilia may cover the entire surface of a cell. • The function of cilia and flagella include locomotion for one-celled organisms and to move substances over cell surfaces in multi-celled organisms.

19. ORGANELLES NOT FOUND IN PLANT CELLS 2. CENTRIOLES • Two tiny cylindrical structures located near the nuclear envelope. Their exact function is unknown but they help assemble the spindle fibers that pull chromosomes apart during mitosis.

20. FOUND ONLY IN PLANT CELLS 1. CELL WALL • The cell wall is a rigid organelle composed of cellulose and lying just outside the cell membrane. • The cell wall gives the plant cell its box-like shape and protects the cell. • The cell wall contains pores, called plasmodesmata, which allow materials to pass through the cell wall so they can enter and leave the cell through the cell membrane.

21. FOUND ONLY IN PLANT CELLS 2. PLASTIDS • Plastids are double membrane bound organelles. It is in plastids that plants make and store food. Plastids are found in the cytoplasm and there are two main types: • Leucoplasts - colorless organelles which store starch or other plant nutrients. ( example - starch stored in a potato) • Chromoplasts - contain different colored pigments. The most important type of chromoplast is the chloroplast, which contains the green pigment chlorophyll. This is important in the process of photosynthesis.

22. FOUND ONLY IN PLANT CELLS 3. CENTRAL VACUOLE • The central vacuole is a large fluid-filled vacuole found in plants. 4. CHLOROPLASTS • A chloroplast is a structure that contains chlorophyll, a molecule that absorbs sunlight. • Photosynthesis takes place in the chloroplast of a cell.