Lecture 1 The Cell Flashcards
(44 cards)
The Cell
THE CELL
• Cells interact with extracellular environment through active processes (active transport - cell uses energy to do this).
1) Exocytosis: expulsion of materials out of the cell by fusing of a vesicle membrane with the cell membrane
2) Endocytosis: uptake of materials into the cell
THE CELL
Endocytosis:
2 types
a) Pinocytosis: “cell drinking”
b) Phagocytosis:
“cell eating”
Structure of cell
CELL MEMBRANE
•
aka plasma membrane
• Surrounds the cell
Composed of a phospholipid bilayer and proteins:
- phospholipids: act as diffusion regulators.
- proteins: structural reinforcements and receptors for certain hormones, neurotransmitters and immunoglobulins (antibodies).
• Semipermeable:
- provides a selective barrier that regulates transport of substances into and out of the cell.
CYTOPLASM
• aka cytosol
• Clear liquid enclosed in the cell by the cell’s membrane.
• Includes organelles and inclusions and also spaces or cavities called vacuoles.
• Provides a medium (fluid)
in which other
organelle’s function.
ORGANELLES
• Organelles are metabolically active specialized structures within the cell.
• Organelles allow each cell to function according to its genetic code.
• Major organelles are:
• Nucleus
• Mitochondria (sing: mitochondrion)
• Ribosomes
• Endoplasmic reticulum
• Golgi Apparatus
• Lysosomes
• Cytoskeleton
NUCLEUS
•
Plural - nuclei
Largest, densest organelle
Usually single nucleus present but cells can be:
- Binucleated:
- cardiac muscle cells
- parenchymal liver cells
- Multinucleated:
- osteoclasts
- skeletal muscle cells
• Production of:
- 1) DNA (deoxyribonucleic acid):
cell’s genetic information
- 2) RNA (ribonucleic acid):
carries info from the DNA to sites of actual protein synthesis in the cytoplasm.
Present in all cells except mature red blood cells and blood platelets.
COMPONENTS of a NUCLEUS
• NUCLEOLUS:
-contained in the nucleus
-produces rRNA and nucleotides of two other types of RNA
• CHROMATIN (form of DNA):
-contains chromosomes
-looks like diffuse stippling when the cell is viewed at lower-power microscopically
• NUCLEOPLASM:
-fluid portion that contains important proteins
NUCLEAR ENVELOPE:
-a double layered membrane
ENDOPLASMIC RETICULUM
• The ER consists of parallel membrane-bound channels.
• All membranes are interconnected.
• Connected to cell membrane, the nuclear membrane and some organelles (“highway system for the cell”).
• Primary function: modification, storage, segregation and transport of proteins that the cell manufactures.
• Can be classified as rough or smooth.
ROUGH ENDOPLASMIC RETICULUM
• Contains ribosomes on its outer surface
• Ribosomes - particles composed of protein and
RNA which synthesize protein (“protein factories”)
The protein molecule can then be transported to Golgi Apparatus for further processing
SMOOTH ENDOPLASMIC RETICULUM
• No ribosomes
• Contains enzymes involved in
manufacturing various lipid molecules and steroid hormones.
Golgi Apparatus
• “Chemical processing and packaging center”
• Second largest organelle
• A stack of 3 to 20 flattened membranous sacs (looks like a stack of pancakes).
• Function: sorts, condenses, packages and delivers proteins from the RER.
• Processes the protein molecule created by the ribosomes.
• Attached to the cell’s membrane and release its contents by exocytosis.
MITOCHONDRIA
• “Powerhouse” of the cell.
- Composed of two membranes: (the inner membrane is folded to increase in surface area forming cristae)
• Most numerous organelle in the cell
• Releases energy from food molecules and transform energy into ATP (adenosine triphosphate).
LYSOSOME
• “Sewer system” of the cell (destroys worn cell parts).
• Membranous sacks produced by the Golgi
Apparatus.
• Contains hydrolytic (hyaluronidase) and digestive enzymes capable of digesting substances that enter cells.
CYTOSKELETON
The components include:
-microfilaments
-intermediate filaments
-microtubules.
• Components give basic stability to the cell as a whole, functioning like reinforced girders.
• The cytoskeleton also compartmentalizes (sorts out) the cytoplasm, creating preferred
“freeways” for the movement of molecules formed by cellular processes.
Cytoskeleton
3 Compnents
• The components include:
-microfilaments
- intermediate filaments
- microtubules.
MICROFILAMENTS:
• Delicate, threadlike, microscopic structures of specialized protein, arranged in meshwork of bundles.
• Cause various kinds of cellular movements (such as in muscle cells as myofibrils).
• Responsible for cell motility.
Microtubules
MICROTUBULES:
• Long slender tubes with diameters 2 or 3 times greater than microfilaments.
• Usually stiff, forming an
interna skeleton within a cell which helps maintain the shape of the cell.
Provides strength to the structure of:
- cilia (shorter, many)
- flagella (longer, few)
centrioles mitotic spindle
CYTOSKELETON
INTERMEDIATE FILAMENTS:
INTERMEDIATE FILAMENTS:
•Various types of thicker, threadlike microscopic structures within the cell.
• Ex: tonofilament - important in intercellular junctions.
INCLUSIONS
INCLUSIONS
• Metabolically inert substances that are transient over time in the cell.
• Consist of cellular products that remain in a cell only temporarily.
• Ex: nutrients such as glycogen, lipids and the pigment melanin.
INTERCELLULAR JUNCTIONS*
INTERCELLULAR JUNCTIONS
Tight Junctions
TIGHT JUNCTONS:
• Closes intercellular space between cells by fusing cell membranes together.
• Prevents the movement or loss of fluid.
• Location:
- cells that line inside of the small intestine
DESMOSOMES:
DESMOSOMES:
• Bind cells together by creating “spot weld between adjacent membranes.
• Location: cells of the outer skin and oral
Desmosomes
Desmosome - Tonofilament Complexes)
