Chapter 2 Flashcards
An organelle is
an internal functional structure
that is located within the cytosol of a cell that carry out specialized functions.
- Some isolate harmful substances or provide environments for reactions not possible in the cytosol.
- some manage transport & maintain fluid balance in the cytosol.
- shapes of some organelles=elaborate cuz each organelle is adapted to perform a specific function
Plant cells differ from animal cells BECAUSE
plants and animals have very different
requirements for obtaining food and energy.
fungi have many of the same organelles as plants & animals . Fungi-like animals are heterotrophic, while the protist kingdom includes both heterotrophs and photosynthetic autotrophs
The most complex of all cells are
those of some single celled protists.
plasma membrane is
a dynamic (characterized by constant change-GOOGLE) barrier that surrounds the cytosol of the cell
- maintains an internal environment that allows
the organelle to carry out its particular function.
- control the amounts and types of substances that move in and out of the cell
The nucleus is
an organelle that contains & protects almost all the DNA (genetic material) in a eukaryotic cell
–> keeps DNA away from activity of the cytosol & from the metabolic reactions that might damage it
- Small amounts of DNA are present in 2
other organelles= chloroplasts & mitochondria
The nuclear envelope is
a two-layer membrane that surrounds the nucleus of a eukaryotic cell –> conists of 2 lipid bilayers folded together
- the outer layer connected to the endoplasmic reticulum (ER).
- Various proteins like receptors & transporters, are embedded in these bilayers. Others collect in tiny
pores that span the membrane
–> they help facilitate molecule transport across the nuclear membrane
Transport Across the Nuclear Membrane
Like other membranes, the nuclear envelope permits water and gases to cross freely,
- other substances require specific transporters and pumps located across the nuclear membrane to move between the nucleus and the cytosol.
- This selective transport system controls the entry and exit of molecules, ensuring the appropriate molecules involved in processes like DNA transcription into RNA and protein synthesis move in and out at the right times.
Nuclear membrane: Regulation and Protection of DNA
By regulating what molecules cross the nuclear membrane, the cell safeguards its DNA and controls RNA and protein production.
Proteins attached to the inner surface of the nuclear envelope help organize and anchor DNA, and play a role in passing DNA to daughter cells during mitosis.
Nucleolus
The nucleus also contains at least one nucleolus
(plural: nucleoli), a dense irregularly shaped region where subunits of ribosomes are assembled from proteins and RNA.
Nucleoplasm is
is a viscous fluid that is similar to cytosol located in the nucleus contains nucleoplasm, which is enclosed by the nuclear envelope.
The Endomembrane System is
a group of interacting organelles between the nucleus & the plasma membrane
- main function is to make lipids, enzymes,
and other proteins for secretion or insertion into cell membranes
- other specialized functions include destroying toxins & recycling wastes
- The components of the endomembrane system vary among different types of cells, but the most
common components are: Nucleus, the ERs, Golgi body, & vesicles
The Endoplasmic Reticulum is
a membrane-bound organelle that is folded into flattened sacs and tubes, and is an extension of the nuclear envelope
Rough ER
- areas of endoplasmic reticulum with ribosomes attached to the surface
- 1000s of ribosomes are attached to the outer surface of rough ER –> ribosomes synthesize polypeptide chains, which are released into the interior of the ER. Inside the ER, the proteins fold and take on their complex structure.
- Some of these proteins become part of the ER membrane, & others are sent to different cell parts.
- Cells that produce, store, & secrete large amounts of protein, such as gland cells in the pancreas, contain a lot of rough ER. –> Ex, ER-rich gland cells in the pancreas make and secrete enzymes that help to digest food in the small intestine.
Two kinds of ER—rough ER and smooth ER—are named for their _______________________________________
appearance in electron micrographs
smooth ER
areas of the endoplasmic reticulum without attached ribosomes
- does not make proteins
- Some of the polypeptides made in the rough ER end up in the smooth ER as enzymes
–>These enzymes produce most of the cell’s membrane lipids.
- They also break down carbs, fatty acids, & some drugs & poisons.
Vesicles are
a small, membrane-bound, saclike organelles, organelle that may transport, store, or digest substances within a cell
- are many types of vesicles with many different functions
- Some types transport proteins from one organelle to another, or to and from the plasma membrane
A peroxisome is
a type of vesicle
- contains enzymes that digest fatty acids & amino acids
- Peroxisomes form & divide on their own and have a variety of functions like inactivating hydrogen peroxide, a toxic by-product of fatty acid
breakdown
- Enzymes like catalase, in the peroxisomes convert hydrogen peroxide to H2O & O2, or they use hydrogen peroxide in reactions that break down alcohol & other toxins
Vacuoles
- a type of vesicle in both plant and animal cells
a liquid-filled organelle that stores waste and aids in cellular metabolism and water balance - Vacuoles seem empty under microscope but act like “trash cans,” isolating and disposing of wastes, debris, and toxic materials.
- fluid pressure keeps structures firm
Vacuoles: plants vs animals
- Plant cells have a large central vacuole where amino acids, sugars, ions, wastes, & toxins accumulate in a water-filled space.
- The fluid pressure inside the central vacuole helps keep plant cells, and structures like stems and leaves, firm.
- Usually, the central vacuole takes up 50 to 90 % of the cell’s interior
- Plant cells have bigger vacuoles than animal cells as they need to store food & water. This is cuz plants don’t have the ability to move freely like animals. (GOOGLE)
Lysosomes are
a small vesicle that contains digestive enzymes that aid in waste disposal
- its a type of vesicles that contain powerful digestive enzymes
- They fuse with vacuoles that carry particles or molecules for disposal, such as worn-out cell components.
- Lysosomal enzymes empty into these vacuoles and digest their contents.
A Golgi Body is
an organelle with folded membranes that usually looks like a stack of pancakes where the final packaging of proteins occurs
- Enzymes in a Golgi body put finishing touches on polypeptide chains and lipids that have been
delivered from the ER.–> They attach phosphate groups or sugars, & they cleave certain polypeptide chains.
- The end products (membrane proteins, proteins for secretion, and enzymes) are sorted & packaged into new vesicles that carry them to the plasma membrane or to lysosomes
- vesicles like lysosomes are found near it
Mitochondria are
The mitochondrion (plural: mitochondria) is an organelle with two membranes; the site of most
ATP synthesis during aerobic cellular respiration
- In plants & animals, most ATP is produced in a series of reactions that occur inside the mitochondria & require O2 from the breath u take
- These reactions can extract more energy from organic compounds than any other metabolic pathway.
The number of mitochondria varies based on….
the type of cell and the type of organism
- Cells that have a very high demand for energy tend to have many mitochondria.
- Ex, a single-celled yeast (a type of fungus) may have only one mitochondrion, whereas a human skeletal muscle cell may have a >= 1000.
Mitochondria Structure
Typical mitochondria=1-4 μm in length, few are as long as 10 μm.
- some are branched
- can change shape, split in two, and fuse together
- A mitochondrion has 2 membranes: 1 highly folded inside the other
–> This arrangement creates 2 compartments:
1) the mitochondrial matrix= the interior of the mitochondrion
2) the intermembrane space= the space between the 2 mitochondrial membranes