Cell Organelles

Lindsey Bily Anatomy & Physiology 2011-2012

Austin High School

Cell Theory

• Developed by Matthias Shleiden and Theodor Schwann.

• The cell is the fundamental organizational unit of life.

• All living things are composed of cells.

Cell Membrane

Cell Membrane

Cell Membrane

• Made up of a phospholipid bilayer.

• A phospholipid has a hydrophilic “head” and a hydrophobic “tail”

• Glycoproteins and glycolipids attached to the outer surface and act as markers “self vs. non-self”

• Cholesterol is present to stabilize the membrane.

Cell Membrane

• Membrane proteins are embedded and act as gates or receptors for other chemicals.

Cell Organelles

• “Little Organs”

• Cytoplasm contains the organelles and cytosol.

Endoplasmic Reticulum

• A network of channels in the cytoplasm. Transports molecules around the cell.

• Rough ER is studded with ribosomes.• Smooth ER synthesizes lipids.

Ribosomes

They make proteins.

Ribosomes

• Ribosomes on the ER make proteins for export out of the cell.

• “Free” ribosomes make proteins for the cell’s own use.

Golgi Apparatus

• Receive newly synthesized proteins and lipids from the ER.

• Modify them so that they are ready to leave the cell.

• Carbohydrates, phosphorus, or lipids may be added to the proteins.

Golgi Apparatus

Lysosomes

Vesicles that have detached from the Golgi Apparatus and Vesicles that have detached from the Golgi Apparatus and Contain enzymes to break down cellular components. Contain enzymes to break down cellular components. ““Cellular Garbage Disposals”Cellular Garbage Disposals”

Lysosomes

• White blood cells engulf cells and digest them in their lysosomes.

This picture is of Staph bacteria (red) being digested by lysosomes.

Lysosomes

• This is a lysosome in the process of digesting a mitochondria!

Peroxisomes

Contain enzymes (peroxidase and catalase) that Contain enzymes (peroxidase and catalase) that detoxify harmful substances that enter the cell. detoxify harmful substances that enter the cell. Usually found in great numbers in kidney and liver Usually found in great numbers in kidney and liver cells.cells.

Mitochondria

• Surrounded by a double membrane.

• They contain their own mitochondrial DNA.

• Are thought to have been free living bacteria millions of years ago.

• Site of cellular respiration to produce ATP (energy).

The Nucleus

• The largest organelle. Usually in the center in the cell.

• Contains DNA.• The nucleolus

contains rRNA that helps to form ribosomes.

Cytoskeleton

The cell’s internal supporting framework.

Besides giving the cell shape and structure, these filamentous elements produce movements of structures within the cell and movements of the cell itself.

1. microfilaments

2. microtubules

3. intermediate filaments

Microfilaments

Smallest of the cell fibers.

Very slender strands of proteins.

Actin: They attach the cell membrane and the nuclear envelope to the cytoplasm.

Myosin: Actin interacts with the thicker (18 nm) myosin microfilaments to produce cell contractions. This arrangement is abundant in skeletal muscle cells.

Actin & MyosinActin & Myosin Skeletal MuscleSkeletal Muscle

Intermediate Filaments

Intermediate in thickness between the actin (thin) and myosin (thick) microfilaments.

They are insoluble and the most durable of the cytoskeletal components.

Maintain the cell’s shape and anchors the organelles.

Microtubules

• polymers of tubulin. Microtubules are important for maintaining cell structure, providing platforms for intracellular transport, forming the spindle during mitosis, as well as other cellular processes.

• Microtubules can serve as an anchorage or “footpath” for proteins that behave as molecular motors. These specialized proteins, kinesin and dynein produce the intracellular movements of small structures like vesicles.

• Microtubules within cilia and flagella produce the whip-like motions of these organelles.

Microtubules

Centrosome & Centrioles

• Centrosome is an area of cytoplasm near the nucleus that builds and breaks microtubules.

• Centrioles are composed of microtubules in the centrosome that are involved in mitosis.

Cell Extensions

• Projections that extend from the plasma membrane.

• Microvilli: tiny fingerlike projections that are involved in absorption. Found in intestinal cells.

• Cilia and Flagella: made of microtubules and involved in movement.

-Cilia in trachea keep contaminated mucus from going into the lungs. Cilia in female reproductive tract keeps the ovum (egg) moving towards the uterus.

-Flagella on sperm allow it to “swim”.

Ciliated Ciliated TracheaTrachea

Microvilli Microvilli in small in small intestineintestine

Flagella on Flagella on sperm cells sperm cells covering an covering an eggegg

Cell Connections

• Cells are held together by nets that surround groups of cells (ex. Muscle cells), or cells have direct connections to each other.– Desmosomes: “spot welds” that hold adjacent

cells together

– Gap Junctions: membrane channels of adjacent plasma membranes adhere to each other.

• Form gaps or tunnels that join the cytoplasm of two cells

• fuse two plasma membranes into a single structure

Tight Junctions: “collars” of tightly fused membrane. Molecules cannot permeate.

Desmosomes in skin Desmosomes in skin cellscells

Gap junctions Gap junctions (green) between (green) between cardiac cellscardiac cells

Tight JunctionsTight Junctions(green) between (green) between Intestinal Intestinal Epithelial cellsEpithelial cells