Cell Organelles

• An organelle is an internal functional structure located within a cell's cytosol.
• Organelles interact and complement each other in both form and function inside a cell.
• In eukaryotic cells, organelles perform specialized functions.
• Some organelles isolate toxic substances or create environments for reactions that cannot occur in the cytosol.
• Other organelles transport substances, maintaining fluid balance.
• Organelles have elaborate shapes suited to their specific functions.
• Plant and animal cells differ in their food and energy requirements, impacting their organelles.
• Eukaryotic plant and animal cells share different organelles; a feature also shared with fungi
• Fungi-like are heterotrophic; kingdom protista include both heterotrophs and photosynthetic autotrophs
• The single-celled protists showcase the most intricate cells.
• Membranes bound the cells and many organelles and regulate substance movement
• The plasma membrane creates a barrier around the cell's cytosol.
• Organelle membranes maintain an internal environment for specific functions.
• Organelles need to work in teams to maintain processes and bodily functions and maintenance
• Substances are able to move between organelles as well as the plasma membrane
• Metabolic pathways take place in a series of different organelles
• Cells reproduce to generate more cells.

Cytoplasm vs. Cytosol

• Cytoplasm refers to all internal components of a cell, excluding the nucleus.
• Cytosol refers to the liquid portion of the cell.

Nucleus

• Nucleus presents in almost all eukaryotic cells with DNA that protects genetic material, separating it from cytosol activity and metabolic reactions.
• The nuclear envelope is a double membrane that surrounds the nucleus.
• The nuclear envelope consists of two lipid bilayers and is continuous with the endoplasmic reticulum.
• Membrane proteins within the bilayers act as receptors, transporters, or form pores.
• The nuclear envelope allows water and gases to cross freely.
• Transporters and pumps regulate the movement of other substances between the nucleus and the cytosol.
• The nuclear membrane regulates molecule passage in amount and time which controls the production of RNA and proteins and protects DNA .
• Proteins attached to the inner nuclear envelope organize DNA molecules.
• During mitosis, these proteins aid in DNA transfer to daughter cells.

Nucleolus

• Nucleolus is enclosed by the nuclear envelope.
• Nucleolus contains nucleoplasm, a viscous fluid which is similar to cytosol.
• Nucleolus contains at least one nucleolus, which is a dense irregularly shaped region
• Nucleolus are important areas where subunits of ribosomes are assembled from proteins and RNA

Endomembrane System

• The endomembrane system is a group of interacting organelles between the nucleus and plasma membrane.
• The endomembrane system’s components vary across different cells.
• The endomembrane system its main function is to produce lipids, enzymes, and proteins for secretion or insertion into cell membranes.
• The endomembrane system has specialized functions like destroying toxins and recycling wastes.

Endoplasmic Reticulum (ER)

• Endoplasmic Reticulum (ER) is an extension of the nuclear envelope.
• ER forms a continuous compartment and is folded into flattened sacs and tubes.
• Rough ER and smooth ER are called for their appearance in electron micrographs.
• Rough ER has ribosomes on its surface that synthesize polypeptide chains, released into the ER's interior.
• Proteins get their complex structure and fold inside the ER.
• Some proteins become part of the ER membrane, other proteins travel to different destinations.
• Cells that secrete, make and store proteins have a lot of rough ER.
• Smooth ER lacks ribosomes and doesn't produce proteins.
• Some polypeptides from the rough ER become enzymes in the smooth ER.
• The smooth ER produces most of the cell membrane lipids.
• The smooth ER can also decompose carbohydrates, drugs, fatty acids and poisons.

Vesicles

• Vesicles are membrane-enclosed, sac-like organelles that form by budding from other organelles or the plasma membrane.
• Many vesicles transport the molecules between organelles.
• Peroxisomes are enzyme containing vesicles that digest fatty acids and amino acids
• Peroxisomes have functions like inactivating hydrogen peroxide and breaking down fatty acids, and divide on their own.
• Enzymes use hydrogen peroxide to break down alcohol, convert it to water, and produce oxygen.
• Vacuoles contain wastes, debris, and toxic materials thus isolating and storing them.
• Large central vacuole is present in plant cells, the central vacuole accumulates amino acids, ions, sugars, toxins and water, that makes structures firm.
• The central vacuole in plant cells makes 50-90% of the cell’s interior.

Lysosomes

• Lysosomes contain powerful digestive enzymes.
• Lysosomes fuse with vacuoles that carry particles, molecules for disposal and break down components
• Lysosomal enzymes empty into the vacuoles to digest their contents

Golgi Bodies

• The vesicles release and fuse their contents in the Golgi Body
• Golgi Body looks like a stack of pancakes with a folded membrane
• Enzymes in the Golgi body put finishing touches on polypeptide chains and lipids.
• Golgi bodies sort and package materials, then package into new vesicles and carry them to other lysosomes or the plasma membrane

Mitochondria

• Mitochondria specialize in producing ATP.
• Most cells have mitochondria.
• Most ATP in plants and animals is produced inside the mitochondria during reactions that need-require oxygen.
• These reactions extract more energy than any metabolic pathway and require oxygen as the breath comes in, to be used by trillions of energy demanding cells
• Mitochondria are similar to bacteria in size, form, and biochemistry.
• Mitochondria have their own DNA and ribosomes.
• The mitochondrial matrix and intermembrane space are the two mitochondrial compartments.
• Mitochondria may have evolved from aerobic bacteria through endosymbiosis.

Plastids

• Plastids are membrane-enclosed structures, that perform storage or photosynthesis in plants and algae
• Common types of plastids are chromoplasts, amyloplasts and chloroplasts
• Plastids include chloroplasts, useful for photosynthesis
• Most chloroplasts are oval or disk-shaped.
• Enclosing the stroma are two outer membranes
• Chloroplasts are similar to photosynthetic bacteria and may have evolved through endosymbiosis.
• Chromoplasts produce and store other pigments than chlorophyll
• Amyloplasts ore unpigmented plastids that commonly store starch grains, in seeds, stem cells, and tubers
• Amyloplasts can act as the cells gravity sensors

Cytoskeleton

• The Cytoskeleton is a system of protein filaments between the plasma membrane and nucleus
• The Cytoskeleton parts move, reinforce and organize cell structure
• Some parts of the cytoskeleton are permanent while others form at specific times

Microtubules

• Microtubules area long and hollow cylinders, contain subunits of protein tubulin, and create cellular processes.
• Microtubules can rapidly disassemble or assemble like when they split chromosomes during cell division
• Microfilaments are strengthen or change the shape of cells
• Microfilaments are fibers of protein actin to drag or extend the cell’s edge in different direction
• Actin and microfilaments of myosin in muscles bring contraction
• Intermediate filaments are the most stable part of the cell’s cytoskeleton made of fibrous proteins, important for strengthening structures

Cilia and Flagella

• Flagella and cilia are organized microtubule groups
• Flagella propels cells such as sperm.
• The constant beating of cillia moves fluid and cells
• Microtubules stabilize arrays of spokes and links
• Spokes come from centrioles and remain near the structure for support
• Pseudopods are used by amoebas and other cells to move that involves lobes and elongates microfilaments move the lobe

Cell Wall

• A cell wall surrounds the plasma membrane in eukaryotic and prokaryotic cells
• The cell wall protects and gives the cell its shape
• The cell wall allows water and solutes to pass
• Plant and cells walls consist of a primary wall and a secondary cell wall from growth occurring later on
• Cuticle helps parts exposed and prevents water loss on hot and dry days
• The primary cell wall is pliable in growing plant cells
• Inner surface material and tissues in plant cells that stop enlarging become firm and create a secondary wall

Extracellular Matrix (ECM)

• The ECM is a a complex mixture of fibrous protein and it supports/anchors and organizes cells
• The cell is supported and is the connection with the surroundings
• A cell junction facilitates cells to connect and interact with other surroundings, sending molecules and signals