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AP Biology Organelles List

Updated: Mar 26, 2019

Author: Lili Wang


Cell Membrane

  • Structure

  • phospholipid (hydrophilic head and hydrophobic fatty acid tails) bilayer

  • embedded channel proteins, peripheral membrane protein, integral membrane protein, alpha-helix protein, globular protein, glycoproteins, cholesterol, and glycolipid

  • semi-permeable and fluid-mosaic model (cell membrane is fluid)

  • Function

  • protects the cell from its surroundings

  • regulates transport of substances in and out of the cell and organelles

  • receives chemical messengers from other cells

  • Found in plant and animal cells, prokaryotic and eukaryotic cells (though prokaryotic cells don’t have membrane bound organelles)

Cell Wall

  • Structure

  • outside of the cell membrane

  • made of carbohydrates

  • primary cell wall is thin and flexible (formed while the cell is growing), secondary cell wall is a thick layer (formed inside the primary cell wall after the cell is fully grown), middle lamella is rich in pectins (functions together to cement the two adjoining cells together of the cell wall)

  • Function

  • protective, semi - permeable, outer layer of a plant cell

  • give cells strength and structure, filter molecules that pass in and out of the cell, protects it from infection, prevents over expansion, and prevents water loss.

  • Found in: prokaryotes (peptidoglycan), plant (cellulose), and in fungi (chitin)

Centrioles

  • Found in all cells of most eukaryotes (not plants or fungi)

  • Structure

  • part of the cytoskeleton

  • nine groups of microtubules (each group has 3 microtubules) organized in a circle, they are arranged perpendicular to one another to form the centrosome (9+0 arrangement).

  • Function

  • Considered microtubule organizing centers in the cytoplasm (microtubules are made of protein tubulin; provides support and motility for cellular activities; found in the spindle apparatus)

  • 2 centrioles together form a centrosome which is involved in creating the microtubules (spindle fibers) in cell reproduction, also known as mitosis, move towards opposite poles of the cell in mitosis, then organize the mitotic spindle allowing it to connect to the chromosomes and split them apart (allows new cells with the same DNA can form)

  • positions the cilia and flagella in cells that have those organelles

  • help with the development of embryos after fertilization.

  • Location - found in centrosomes (in the cytoplasm) and position of the nucleus will change based on the position of the centrioles in the centrosome

Chloroplasts

  • Structure - has an outer membrane and an inner membrane (make up the chloroplast envelope), inside the membrane is a thylakoid membrane (contains a thylakoid space), found in stacks called grana, have circular DNA, has its own 70S size ribosomes to make their own proteins

  • Function - primary site of photosynthesis, capture light energy and turn it into chemical energy (sugars)

  • Eukaryotes only (plants and protists but not animal cells)

Cilia

  • Structure - microtubule extensions projecting from the cell, about 0.25 um in diameter and 2-25 um long, tends to be many cilia on each cell (there are often hundreds)

  • Function - can be used for cell movement and signaling/communication between cells, move fluid over the surface of the cell (cilia move back and forth to pull fluids across the cell, like oars moving through water.

  • Ex. cells in your windpipe have cilia to sweep mucus out of the lungs

  • Found in eukaryote and prokaryote cells (typically only animal cells)

  • Microtubules - main structural base for cilia and flagella for cell movement they are arranged in a 9 + 2 pattern (9 microtubules form an outer circle and are connected to 2 center microtubules), for non-movement functions arranged in 9 + 0 pattern (without the central microtubules), Dynein motor proteins between the microtubules use ATP to move the cilia/flagella.

Cytoskeleton

  • Structure - made up of different sized fibers, microfilaments are extremely small helically shaped filaments made of G-actin proteins, intermediate filaments are slightly larger and are made of keratin-based filaments, microtubules are larger hollow cylinders, has some motor proteins that move the fibers around and are powered by ATP.

  • Function - gives the cell its shape, offers support, and helps the cell move (facilitates movement by microfilaments, intermediate filaments, and microtubules), and function as a pathway for vesicles, assists the formation of vacuoles and transportation of communication signals between cells, helps organelles move w/in the cell

  • Found in both eukaryotic and prokaryotic cells (though scientists are not sure that they have identified all the parts of the prokaryotic cytoskeleton), in both plant and animal cells.

Desmosomes

  • Structure - align in a sheet like structure, made up of three key parts (two that are within the cell and one that is outside of the cell) → Inside of the cell, keratin filaments mechanically stabilize the cell protect it from physical stress, the protein desmoplakin then acts as a link between the keratin filaments and the cadherin proteins, the cadherin proteins on the outside of the cell adhere the cell to another cell. if one fails, the whole intercellular adhesion system fails.

  • Function - to adhere cells together, found in cells that a subject to a lot of mechanical force (like muscle tissue in the heart and the epidermis of the skin), also allow for movement and flexibility.

  • Found in eukaryotic cells and only exist in animal cells.

Endoplasmic Reticulum

  • Structure - "an interconnected network of flattened, structures known as cisternae."

  • Function - manufacturing and packaging system of the cell, transports proteins and carbohydrates to other organelles (ie. Lysosomes, Golgi Apparatus, the Plasma Membrane, etc.).

  • Rough ER - synthesize and export proteins and glycoproteins to other areas of the cell and the body. The process of constructing proteins by the rough ER is called translation. To get the proteins to the cell membrane the rough ER packs them into "vesicles (tiny compartments of lipid bilayer that store molecules) which then translocate to the cell membrane."

  • Smooth ER - "produce cellular products like lipid hormones (estrogen and testosterone) and carbs.

  • Found in eukaryotes (plants and animals), part of the endomembrane system

Extracellular matrix

  • Structure - proteoglycans (carbohydrate polymers attached to proteins), fibrous proteins including collagen (provide structural support to cells), elastin (allow tissues to stretch and return to their original shape), integrins (proteins, connect the cytoskeleton (inside the cell) with the extracellular matrix (outside the cell) through the cell membrane)

  • Function - determine how a tissue looks and function), provide structural support for cells (position cells within tissue), guides cell division, growth, and development (integrin proteins can signal to the cell what to do depending on tension in the tissue, basically helps determine how cells all relate to each other in a tissue

  • Found in all cells

Flagella

  • Structure - different in prokaryotes and eukaryotes

  • Eukaryotic - flagella are hair like structures that protrude from the cell body. The core is made up of nine pairs of microtubules surrounds by two pairs of microtubules (9+2), each microtubule is composed of the protein tubulin, base of the flagella is connected to the cell basal body

  • Bacterial flagella - have a filament and tip which make a helically shaped structure caused by protein flagellin, connected by the hook (bass end) to the basal body which is in cytoplasmic membrane and cell wall, flagellar filament connects the hook to the tip.

  • Function- movement in cells, rely on ATP for energy to rotate the tail of the flagella like a motor and cause movement

  • In bacteria and fungi - flagella causes water currents necessary for respiration and circulation within the cell.

Gap Junction

  • Structure - 6 proteins (individually = connexin, all together = connexon) connect 2 cell membranes from adjacent cells, two connexons form an intercellular channel which can open and close, connect the cytoplasm of the two cells.

  • Function- connect the cytoplasm of 2 adjacent cells (allows for an exchange of ions, molecules, and electrical signals), cells like heart cells have these

  • Found only in animals cells and eukaryotes.

Golgi Apparatus

  • Structure -

  • Cis Golgi network - entry area to golgi apparatus

  • Golgi stack - 3-6 flattened sacs called cisternae, divided into 3 working areas (cis cisternae, medial cisternae, and trans cisternae)

  • Trans golgi network - final reactions take place, biochemicals packaged into vesicles

  • Function - takes products from the rough ER through vesicles, unloaded in cis network (sent back if wrongly delivered), products will travel through the cisternae and be processed and sorted (Ex. if the SER ships carbs, and the RER ships proteins, the golgi can modify this into a glycoprotein and ship this out), goods are sent out, part of the endomembrane system

  • Present in eukaryotic cells: plant, fungi, and animal cells.

Lysosomes

  • Lysosome: A lysosome is a vesicle that holds a lot of different enzymes.

  • Structure - spherical shaped, single layer membrane with a lipid bilayer, have transport proteins on the outside of the membrane and the inner part of the membrane is filled with a hydrolytic enzyme mixture, exact shape and size differs between individual lysosomes but are generally similar, exist in more acidic environments.

  • Function - breakdown of materials in the cell (break down macromolecules such as proteins, nucleic acids, carbohydrates, and lipids), break down unwanted waste from other cells, help maintain homeostasis, repair plasma membranes, cell signaling, and energy metabolism (use of the enzymes stored inside the lipid bilayer) → disposal system (digests old organelles in autophagy, breaks down solids in phagocytosis, and programmed cell death)

  • Found in both plant and animal cells (Ex. white blood cells), eukaryotes (not in fungi)

Mitochondria

  • Structure - made up of two membranes (an outer membrane which contains the cell, and an inner membrane which folds, creating a layered structure called cristae), cristae increases the surface area of the cell (allowing diffusion to occur faster), cristae provide locations for ATP production, mitochondrion matrix (gel-like substance) contains the mitochondrial DNA (circular DNA, creating the proteins using 70S ribosomes which the mitochondria use to function)

  • Function - perform cellular respiration (use oxygen to generate ATP by extracting energy from sugars, fats, and other fuels), ATP is used for cell functions

  • Found in eukaryotic cells, and both plants and animals

Nucleus

  • Structure - enclosed nuclear membrane, contains the majority of the cell's genetic material (organized as DNA and RNA molecules along a variety of proteins), takes up about 25% of the cell's volume, nuclear membrane has small pores which enable rRNA (messenger RNA) to pass through the membrane, DNA and RNA are contained in the nucleolus (middle of the nucleus)

  • Function - storing of the cell's hereditary material, or DNA, and the coordinating of the cell's activities (including cell growth, protein synthesis, intermediary metabolism, and cell/DNA reproduction), forms messenger RNA (leaves the nucleus to form amino acid sequences in a ribosome), part of the endomembrane system

  • Found in both plant and animal cells but only occurs in eukaryotic animal cells.

Peroxisome

  • Structure - made of a phospholipid bilayer with many membrane-bound proteins, contain some enzymes at very high concentrations (occasionally appearing to have a crystalloid core), can divide into 2 organelles (as it grows in size due to the ingress of proteins and lipids)

  • Function - use molecular oxygen for metabolic processes, associated with lipid metabolism (mostly β–oxidation of fatty acids, the mobilization of lipid stores in seeds, cholesterol biosynthesis and steroid hormone synthesis) and processing reactive oxygen species.

  • In plants - play important roles in seed germination and photosynthesis.

  • In animals - sites for some amount of lipid biogenesis (esp of special phospholipids called plasmalogens), prominent part of kidney and liver cells (detoxifying and oxidizing molecules, metabolic byproducts and drugs)

  • Ex. they make catalase which can help break down the waste product H2O2.

  • Found in eukaryotes (both plants and animals)

Plasmodesmata

  • Structure - microscopic (50-60 nm diameter), 3 main layers —> plasma membrane (continuous extension of the cell membrane so that connected cells share membranes), cytoplasmic sleeve (cytoplasm running between connected cells, surrounds desmotubule), desmotubule (derived from smooth ER of connected cells)

  • Function -

  • allows cytoplasmic continuity between plant cells

  • enables transport between cells

  • opening size can be modified to enable/restrict transport

  • Found in plants (+ some algae)

Ribosomes

  • Structure -

  • In eukaryotic - about 80 proteins and some nucleic acids, exact structure depends on the organism, 2 subunits (1 large and 1 small), 80S ribosome.

  • Smaller subunit (40S) includes 18S RNA (1900 nucleotides long) and 33 proteins

  • Larger subunit (60S) includes Prokaryotic ribosomes are smaller than eukaryotic; it is known as the 70S ribosome

  • Function - synthesizing proteins using the mRNA Free-floating ribosomes (in the cytoplasm), synthesize proteins mainly for the use of the cell, attach to the ER to synthesize proteins (by assembling amino acids that need to be later transported in vesicles leaving the cell)

  • Prokaryotic - only present free-floating in the cytosol, they have the same function (protein synthesis for the cell)

  • Found in prokaryotic and eukaryotic

Tight Junctions

  • Structure - network of branching strands, each strand forms a row of proteins embedded in the plasma membranes.

  • Function - hold cells together by preventing the movement of integral membrane proteins between the apical surface (portion of cell exposed to the outside) and the basolateral surface (rest of the cell surface), limit the passage of molecules and ions through the space between cells (material must actually enter cells through diffusion or active transport in order to pass through tissue)

  • Found in eukaryotic (animal), plants have plasmodesmata

  • Ex. Epithelia

Vacuole (Central)

  • Structure - membrane-bound sac in the cytoplasm

  • In plants - enclosed by a membrane (tonoplast) which is integrated into the endomembrane system, is large

  • In animals - tends to be smaller.

  • Function - (In plants) transports materials through its membrane, storage (salts, minerals, nutrients, proteins), helps in plant growth, important structural component, store waste material and transport it in the cell

  • Control turgor pressure - dictates the cell's rigidity and is associated with the difference between the osmotic pressure (pressure required to prevent fluid from diffusing through a semipermeable membrane separating two solutions of differing concentrations of solute molecules) inside and outside the cell, the central vacuole swells increasing the turgor pressure when water increased which supports the structure of the plant

  • Found in prokaryotic and eukaryotic (animal and plant)

Vacuole (Storage and Contractile)

  • Structure - membrane-bound (phospholipid bilayers) sacs within the cytoplasm of a cell

  • Function -

  • Storage Vacuoles - used for temporary storage of materials (similar to vesicles), store food, enzymes, waste products and other materials

  • Found in eukaryotes (plants and animals)

  • Contractile Vacuole - regulates the water content off the cell, excretes the waste from the cell.

  • Generally they are found in freshwater organisms such as Metazoans. For example, hydra and sponges possess the contractile vacuoles. These vacuoles expand and contract on a regular basis. The water which enters the cells of freshwater organisms through food and osmosis is removed by contractile vacuoles.

Vesicle

  • Structure - large structure within a cell, liquid enclosed by a selectively permeable lipid bilayer

  • Types - formed during process of secretions, all take ATP to function

  • Transport vesicles - membrane bound sacs enclosed by a lipid bilayer that transport materials to and from the cell and between organelles. Package up proteins manufactured in the ribosomes of the endoplasmic reticulum, move this across the cell by motor proteins called microtubules.

  • Secretory vesicle - vesicle that carry substances out of the cell, usually generated from Golgi apparatus

  • Lysosomes - contain special proteins called enzymes which can break down food for the cell, and can combine with transport vesicles to help digest

  • Function - transport materials into cell (lipids and proteins), secrete materials to outside of cell, digests metabolic waste, temporary storage

  • Can fuse with cell membrane and organelle membranes because of lipid bilayer, move in and out of cell.

  • Found in eukaryotic cells but not prokaryote, in both plant and animal cells (vesicles found in plant cells are larger and mostly used to store water and food)

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