Cell Organelles

Section 3.2, Part 3

Objectives

• SWBAT describe the internal structure of eukaryotic cells.

• SWBAT visualize the structures and functions of organelles in plant and animal cells.

Vocabulary• Cytoskeleton (microtubules, intermediate filaments, microfilaments) • Nucleus• Rough endoplasmic reticulum (rough ER)• Smooth endoplasmic reticulum (smooth ER)• Ribosome • Golgi apparatus• Vesicle• Mitochondrion (mitochondria is plural)• Vacuole• Lysosome• Centriole• Cell wall • Chloroplast

Mitochondria (Mitochondrion)

• Mitochondria supply energy to the cell. • They are bean shaped and have two

membranes.– The inner membrane has many folds, which

greatly increases surface are.– The inner folds are where, through a series of

chemical reactions, the food you eat is transformed into useable energy.

Mitochondria

• Mitochondria have their own DNA (in a ring like bacterial DNA) and their own ribosomes.

This suggests that mitochondria were originally free-living prokaryotes that were taken in by larger cells – creating a symbiotic relationship.

Vacuole

• Fluid-filled sacs used for the storage of materials used by cells. – This may include water, food molecules, inorganic ions (not

carbon), and enzymes.– Animal cells contain small vacuoles while plants have large

central vacuoles.

Lysosomes• They contain enzymes, with which they break

down damaged or worn-out cell parts.– They also defend a cell from invading bacteria and

viruses. – They engulf and digest targeted molecules. The

broken down molecule is then moved to the cytoplasm where its parts are used again by the cell.

– They are numerous in animal cells but rare in plant cells.

– Lysosomes are made by the Golgi apparatus.

Lysosomes

The lysosomal enzymes are made in the rough ER in an inactive form. Visicles pinch off from the rough ER and carry the enzymes to the Golgi apparatus. There, the enzymes are packaged, activated and pinched off from the Golgi membrane as formed lysosomes.

Centrosome and Centrioles

• The centrosome is a small region of the cytoplasm that produces microtubles. – In animal cells it contains 2 small structures called

centrioles. • Centrioles are cylinder-shaped organelles made

of short microtubles arranged in a circle. • When the cell is ready to divide, the centrosome

and centrioles double and the 2 new centrosomes move to opposite ends of the cell.

Centrosomes and Centrioles

• They form spindle fibers which attach to DNA and pull the chromosomes apart during cell division (mitosis and meiosis).

Cell Walls

• Surrounds the cell membrane in plants.• Cell walls are rigid and give protection,

support and shape to plant cells.• Cell walls can adhere to each other to help to

support an entire organism. – Example: wood in a tree trunk consists of dead

cells whose cell walls continue to support the entire tree.

Chloroplasts

• They carry out photosynthesis!– They convert solar energy into energy-rich

molecules (i.e. glucose) the cell can use.– They contain chlorophyll

• They are similar to mitochondria in that they have a highly-folded inner membrane.

• They have their own bacteria-like DNA and ribosomes like mitochondria.

Choloroplast