Chapter 6 - The Cell (Part 2) Flashcards
What is a lysosome?
A membranous sac of hydrolytic enzymes that eukaryotic cells can use to digest (hydrolyze) macromolecules. Typically found in animal cells. Lysosomes digest materials taken into the cell and recycle intracellular materials.
*In plant cells and yeast, the same roles are performed by organelles known as lyric vacuoles.
What can lysosomal enzymes hydrolyze?
Proteins, fats, polysaccharides, and nucleic acids. Lysosomal enzymes work best in an acidic environment.
What is phagocytosis?
A process of intracellular digestion where amoebas and many other unicellular eukaryotes eat by engulfing smaller organisms or food particles. A lysosome fuses with the food vacuole and digests the molecules.
What is the process of autophagy?
Lysosomes use enzymes to recycle the cells own organelles and macromolecules. A damaged organelle or small amount of cytosol becomes surrounded by a double membrane and a lysosome fuses with the outer membrane of this vesicle. the lysosomal enzymes dismantle the enclosed material, and the resulting small organic compounds are released to the cytosol for reuse. With the help of lysosomes, the cell continually renews itself.
What are vacuoles?
Diverse maintenance compartments; large vesicles derived from the endoplasmic reticulum and Golgi apparatus.
What are three types of vacuoles?
- Food vacuole - formed by phagocytosis
- Contractile vacuole - pump excess water out of the cell, thereby maintaining a suitable concentration of ions and molecules inside the cell. Found in many freshwater protists.
- Central vacuole - found in many mature plant cells; holds organic compounds and water. Plays a major role in the growth of plant cells, which enlarge as the vacuole absorbs water, enabling the cell to become larger with a minimal investment in new cytoplasm.
What is the endomembrane system?
A complex and dynamic player in the cell’s compartmental organization. Includes the following organelles;
- Nuclear envelope
- Endoplasmic reticulum
- Golgi apparatus
- Lysosomes
- Plasma membrane
What are mitochondria?
Convert energy to forms that cells can use for work. The sites of cellular respiration, the metabolic process that uses oxygen to drive the generation of ATP by extracting energy from sugars, fats, and other fuels.
Found in nearly all eukaryotic cells and have a smooth outer membrane and inner membrane folded into cristae (cristae present a large surface area for enzymes that synthesize ATP). The inner membrane creates two compartments;
- Intermembrane space
- Mitochondrial matrix
The two membranes inclosing the mitochondria are phospholipid bilayers with a unique collection of embedded proteins
What are chloroplasts?
Found in plants and algae and are the site of photosynthesis. Chloroplasts convert solar energy to chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds such as sugars from carbon dioxide and water. Contain the green pigment chlorophyll. The chloroplast is a member of a family of organelles called plastids.
What are 4 similarities between mitochondria and chloroplasts?
- Not part of the endomembrane system
- Have a double membrane
- Have proteins made by free ribosomes
- Contain their own DNA; autonomous organelles that grow and reproduce within the cell
What is the endosymbiont theory?
This theory states that an early ancestor of eukaryotic cells engulfed an oxygen-using non-photosynthetic prokaryotic cell. Eventually, the engulfed cell formed a relationship with the host cell in which it was enclosed, becoming an endosymbiont (a cell living within another cell).
What is cristae?
The inner membrane that divides the mitochondrion into two internal compartments.
- Intermembrane space
- Mitochondrial matrix - enclosed by the inner membrane. The matrix contains many different enzymes as well as the mitochondrial DNA with ribosomes. Enzymes in the matrix catalyze cellular respiration.
What is contained in the structure of a chloroplast?
Double membranes separated by an intermembrane space partition the chloroplast from the cytosol.
- Thylakoids - flattened, interconnected membranous sacs , stacked to form a granum
- Stroma - the fluid outside the thylakoids, and contains the chloroplast DNA and ribosomes as well as many enzymes
* The membranes of the chloroplast divide the chloroplast into three compartments; the intermembrane space, the stroma, and the thylakoid space*
* Chloroplasts have dynamic behavior and are mobile and their shape is changeable. They move around the cell along tracks of the cytoskeleton*
What are plastids? What are the three different types of plastid organelles?
Plastids are found in cells of photosynthetic eukaryotes and include a closely related family of three types of organelles;
- Chloroplasts
- Chromoplasts - pigments that give fruits and flowers their orange and yellow hues
- Amyloplasts - a colorless organelle that stores starch (amylose)
What are peroxisomes?
Specialized metabolic compartments bounded by a single membrane. Contain enzymes that remove hydrogen atoms from various substrates and transfer them to oxygen, producing hydrogen peroxide (H2O2) as a by product.
Peroxisomes contain more than 50 different types of enzymes, which are involved in a variety of biochemical pathways in different types of cells.
Hold on to enzymes that require oxygen. Some peroxisomes use oxygen to break fatty acids down into smaller molecules that are transported to mitochondria and used as fuel for cellular respiration.
Peroxisomes in the liver detoxify alcohol and other harmful compounds by transferring hydrogen from the poisons to oxygen.
*To provide a compartment for oxidation reactions, peroxisomes are involved in lipid biosynthesis.
What is the cytoskeleton?
A network of fibers extending throughout the cytoplasm. It organizes the cells structures and activities, anchoring many organelles.
What are the 3 types of molecular structures of the cytoskeleton?
- Microtubules - hollow tubes; the thickets of the three components;
- Microfilaments - the thinnest of the three components (aka actin filaments)
- Intermediate filaments - fibers with diameters in a middle range
What are the functions of the cytoskeleton?
- Gives mechanical support to the cell and maintain its shape
- Cell motility - Interacts with motor proteins to produce motility; includes both changes in cell location and movements of cell parts. Cytoskeleton elements and motor proteins work together with plasma membrane molecules to allow whole cells to move along fibers outside the cell.
- Inside the cell, vesicles can travel along “monorails” provided by the cytoskeleton
- May help regulate biochemical activities
More specifically, what are microtubules? What are their functions?
Hollow rods constructed from a globular protein called tubulin. Each tubulin (dimer) is made up of two subunits, consisting of two slightly different polypeptides a (alpha) tubulin and B (beta) tubulin. Because of the orientation of these dimers, the two ends of a microtubule are slightly different and one end can accumulate or release tubulin dimers at a much higher rate than the other, thus growing and shrinking significantly during cellular activities.
- Shape the cell - microtubules are responsible for maintenance of cell shape; cell motility (tracks);
- Separates chromosomes during division - chromosome movements in cell division;
- Guides movement in organelles - organelle movements *(guide vesicles from the ER to the Golgi apparatus and from the Golgi to the plasma membrane)
In animal cells, what do microtubules grow out from?
Centrosome - a region that is often located near the nucleus. The microtubule organizing center. These microtubules function as compression resisting girders of the cytoskeleton.
What are centrioles?
Within the centrosome is a pair of centrioles, each composed of nine sets of triplet microtubules arranged in a ring.
What is cilia and flagella?
In eukaryotes, a specialized arrangement of microtubules is responsible for the beating of cilia and flagella; microtubules containing extensions that project from some cells. These sometimes act as locomotor appendages and help many unicellular eukaryotes propel through water (i.e. sperm of animals, algae, and some plants have flagella). They can move fluid over the surface of a tissue as well (i.e. ciliated lining of the windpipe sweeps mucus containing trapped debris out of the lungs).
How do cilia and flagella differ?
In their beating patterns. A flagellum has an undulating motion like the tail of a fish (*swimming). Longer than cilia. Limited to just one or a few per cell.
Cilia work more like oars, with alternating power and recovery strokes (*racing boat). Cilia also act as a signal receiving antenna for the cell and this function is generally nonmotile. there is only one per cell. Crucial to brain function and to embryonic development.
What do cilia and flagella share in common?
Share a common ultrastructure;
- A core of microtubules sheathed by the plasma membrane - 9 doublets of microtubules are arranged in a ring, with two single microtubules in its center (9 + 2) pattern. This pattern is found in nearly all eukaryotic flagella and motile cilia.
- A basal body that anchors the cilium or flagella - microtubule triplets in a 9 + 0 pattern.
- A motor protein called dynein, which drive their bending movements. A typical dynein has two “feet” that walk along the microtubule of the adjacent doublet, using ATP for energy. The movements of the dynein feet cause the microtubules - and the organelles as a whole - to bend.
