HISS CELLS and MICROSCOPE

• Nucleus:

  • Large structure enclosed within a double membrane
  • Contains chromatin, nucleolus, and nucleoplasm
  • Houses the DNA for directing protein synthesis
• Nucleolus:

  • Large, prominent structure within the nucleus
  • Synthesis of ribosomes
• Nuclear Envelope:

  • Double membrane boundary between cytoplasm and nuclear contents
  • Continuous with rough endoplasmic reticulum
  • Separates nucleus from cytoplasm
• Cytoplasm: responsible for many cellular processes

  • Cytosol : Provides support for organelles
  • Cytosol : Serves as the viscous fluid medium for diffusion
  • Organelles : Carries out specific metabolic activities of the cell
• Endoplasmic Reticulum: consists of network of membranous tubules and sacs called cisternae

  • Rough ER : Synthesis of secretory proteins, cell membrane protein, and organelle protein
  • Smooth ER : Synthesis of lipid ; Glycogen metabolism in liver cells ; Store calcium
• Golgi Apparatus:

  • Major sites for carbohydrate synthesis
  • Sorting and dispatching station for ER products
  • Consists of flattened membranous sacs (cisternae)
  • Golgi stacks have polarity: cis face and trans face
• Lysosomes:

  • Spherical-shaped membrane-bound organelles
  • Formed from the Golgi apparatus
  • Contain hydrolytic enzymes for digesting proteins, polysaccharides, fats, and nucleic acids
  • Principal sites of intracellular digestion
  • Involved in autophagy
• Mitochondria:

  • Double membrane-bound organelles containing circular DNA
  • Energy transformers of cells
  • Synthesize most ATP during aerobic cellular respiration by digestion of fuel molecules in the presence of oxygen
  • Cristae- folds in inner mitochondrial membrane
• Ribosomes:

  • Organelles composed of protein and ribosomal RNA
  • Engage in protein synthesis
  • Bound ribosomes : Produce proteins for secretion, incorporation into the plasma membrane, and within lysosomes
  • Free ribosomes : produce proteins used within the cell
• Peroxisomes:

  • Smaller, spherical-shaped membrane-bound organelles formed from the ER or through fission.
  • Detoxify harmful substances
  • Engage in beta-oxidation of fatty acids to acetyl CoA
  • Contain oxidative enzymes
• Cytoskeleton:

  • Organized network of protein filaments and hollow tubules
  • Includes microfilaments, intermediate filaments, and microtubules
  • Provides mechanical strength, cell shape, locomotion, and intracellular transport of organelles
• Centrosomes:

  • Region near the nucleus from which microtubules sprout
  • Contains a pair of centrioles
  • Organizes microtubules
  • Participates in mitotic spindle formation during cell division
• Plasma Membrane:

  • Composed of a phospholipid bilayer containing cholesterol, proteins, and carbohydrates
  • Forms a selectively permeable boundary of the cell
  • Regulates material movement in and out of the cell
  • Establishes and maintains an electrical charge difference
  • Facilitates cell communication
• Cilia:

  • Move substances over the cell surface
• Flagella:

  • Propels sperm
  • Provide locomotion for the cell
• Microvilli:

  • Increase membrane surface area for greater absorption
• Cell Cycle:

  • Interphase:
  • G1: accumulation of enzymes and nucleotides
  • S: DNA replication
  • G2: preparation for mitosis
  • Mitosis: The only cell cycle that can be routinely distinguished with a light microscope
• Cytoskeleton:

  • Organized network of protein filaments and hollow tubules
  • Microfilaments, intermediate filaments, microtubules
  • Provide mechanical strength to the cell
  • Establish cell shape
  • Assist in cell locomotion
  • Facilitate intracellular transport of organelles
• The formation of ribosomes involves the assembly of the ribosomal precursor RNA with both ribosomal proteins and 5S rRNA. The genes that encode ribosomal proteins are transcribed outside of the nucleolus by RNA polymerase II, yielding mRNAs that are translated on cytoplasmic ribosomes.
• Centrioles are composed of 9 sets of triplet microtubules arranged in a ring ; replicate before cell division. They function as organizing microtubules that serve as the cell's skeletal system,
• Peroxisomes are small vesicles containing oxidative enzymes that produce hydrogen peroxide from various substrates; they play a role in detoxifying drugs and other foreign compounds, breaking down fatty acids, and producing energy through beta-oxidation.
• The cis face of Golgi apparatus is the receiving side near ER while trans face is the shipping side away from ER
• The products of golgi apparatus are: Lysosomes, secretory proteins, and vacuoles
• Golgi apparatus is not physically connected with Cisternae
• Autophagy is your body's process of reusing old and damaged cell parts
• • Microfilaments support the shape and locomotion of the cell.
  • Intermediate filaments provide strength and resistance.
  • Microtubules supports the position of organelles and assists in cellular transport.
• Plasma membrane is composed of Protein, Cholesterol, and Carbohydrates.
• • During interphase, the cell grows and makes a copy of its DNA.
• • During the mitotic (M) phase, the cell separates its DNA into two sets and divides its cytoplasm, forming two new cells.
•  During G1  phase, the cell grows physically larger, copies organelles, and makes the molecular building blocks it will need in later steps.
• •  In S phase, the cell synthesizes a complete copy of the DNA in its nucleus. It also duplicates a microtubule-organizing structure called the centrosome. The centrosomes help separate DNA during M phase.
• •  During the second gap phase, the cell grows more, makes proteins and organelles, and begins to reorganize its contents in preparation for mitosis. G  phase ends when mitosis begins.
• • The G , S, and G  phases together are known as interphase. The prefix intermeans between, reflecting that interphase takes place between one mitotic (M) phase and the next.
• During the mitotic (M) phase, the cell divides its copied DNA and cytoplasm to make two new cells. M phase involves two distinct division-related processes: mitosis and cytokinesis.
• In mitosis, the nuclear DNA of the cell condenses into visible chromosomes and is pulled apart by the mitotic spindle, a specialized structure made out of microtubules. Mitosis takes place in four stages: prophase (sometimes divided into early prophase and prometaphase), metaphase, anaphase, and telophase. You can learn more about these stages in the video on mitosis.
• In cytokinesis, the cytoplasm of the cell is split in two, making two new cells. Cytokinesis usually begins just as mitosis is ending, with a little overlap. Importantly, cytokinesis takes place differently in animal and plant cells.
• A cisterna is a flattened membrane vesicle found in the endoplasmic reticulum and Golgi apparatus.
• Prophase

  • The nucleolus disappears and the replicated chromatin condenses into discrete thread-like chromosomes.
  • The two centrosomes with their now-duplicated centrioles separate and migrate to opposite poles of the cell and organize the microtubules of the mitotic spindle.
  • Late in prophase, lamins and inner nuclear membrane are phosphorylated, causing the nuclear lamina and nuclear pore complexes to disassemble and disperse in cytoplasmic membrane vesicles.
• Metaphase

  • Chromosomes condense further and large protein complex called kinetochores is formed.
  • The cell is now more spherical and microtubules move the chromosomes into alignment at the equatorial plate
• Anaphase

  • Sister chromatids separate and move toward opposite spindle poles by a combination of microtubule motor proteins and dynamic changes in the lengths of the microtubules as the spindle poles move farther apart