CH 2 - The Cell Flashcards
What is protoplasm?
Protoplasm is the living substance of the cell and contains cytoplasm and karyoplasm
What is cytoplasm?
Cytoplasm is the contents of the cell excluding the nucleus
What is karyoplasm
Karyoplasm is the contents of the nucleus
What is cytosol?
Cytosol is the fluid suspension in the cytoplasm
What does amphipathic mean?
It means it has a hydrophobic and a hydrophilic region
What are the three types of endocytosis?
All require ATP
Phagocytosis: Cell eating, such as the engulfing of microorganisms, cellular debris, old worn out cells (Macrophages and neutrophils)
Pinocytosis: Cell drinking, the cell takes in droplets of extracellular fluid which contain the solute molecules.
Cell-Mediated Endocytosis: The capture of macromolecules using receptor proteins in the cell membrane (coated pit). Clathrin is a huge player here
Exocytosis
Vesicles fuse with the cell membrane and release their contents into the extracellular space. ATP is required (Exocytosis is triggered in many cells by a brief release of Ca++ ions into the cytosol.)
Glycocalyx
The carbohydrate chains covalently linked to the transmembrane proteins and phospholipids of the outer membrane.
It has many negatively charged sulfate and carboxyl groups that are involved with making up receptors that participate in functions like: cell recognition, hormone response, and adhesion
Four main functions of the cell membrane
Physical barrier: partitions the inside vs the outside
Cell Communication: think receptors!
Selective structure: regulates ion and molecule flow
Protection and support: maintains cell integrity
Mitochondria
aerobic respiration center
Double membrane
Matrix: Krebs cycle and Fatty Acid Oxidative processes occur here.
Contains mitochondrial DNA (double stranded but circular)
Very gel-like and viscous
Inner Membrane: Electron Transport Chain
Heart has the most
Lysosome
Membrane bound organelle that contains many different types hydrolytic enzymes that only function at low pHs (pH is usually around 5)
They digest: Microorganisms like fungi or bacteria, cellular debris such as old cells, old organelles such as mitochondria.
Very abundant in cells that undergo phagocytosis. Neutrophils and Macrophages are packed with lysosomes
phagosome
A fusion of the cell membrane around a microorganism or senescent cell (A cell that no longer divides).
The phagosome fuses with the lysosome and the enzymes begin digestion.
Tay-Sachs disease
A critical lysosomal enzyme is deficient and lipids can’t be digested. Cells become engorged and neuronal function suffers. Most die before the age of 4
Golgi Apparatus
Involved in the synthesis of carbohydrates and the modification of proteins. (post-translational modification and packaging)
Some proteins are glycosylated, while others have sugars removed instead.
Three main sections:
Cis face: molecules go in
Main Golgi: molecules get processed
Trans face: molecules go out
Three main destinations:
Inside the cell: many are vesicle bound for the lysosomes
Plasma membrane: Golgi repairs and maintains the plasma membrane
Outside the cell: Such as the release of insulin
Many of the cells polysaccharides are made here as well as most of the glycosaminoglycans of the extracellular matrix
In plants the golgi creates hemicellulose and pectin which help make up the cell wall
How are lysosomes formed
They are formed from budding off of the golgi apparatus
Smooth ER
Involved with:
lipid biosynthesis such as phospholipids,
holding and releasing Ca++ ions in a controlled manner (called sarcoplasmic reticulum in skeletal muscles),
steroid biosynthesis,
detoxification of drugs and poisons
In the liver smooth ER contains a large amount of cytochrome 450. It helps catalyze the breakdown of toxic substances.
Cells that are active in the synthesis of steroids, cholesterol, and triglycerides would have a large abundance of what organelle?
smooth ER
What organelle is continuous with the nuclear envolope?
Rough ER
Rough ER
Ribosomes on the rough ER are membrane bound and are involved in protein synthesis
Cells that make enzymes like the pancreas and the GI tract have abundant rough ER
The rough ER works with the ribosome and continues protein assembly. Most proteins are moved to the golgi for final modification. They are either moved to the golgi in vesicles or moved directly from the ER to the golgi
Ribosome
Protein factory
Found in both Eukaryotes and Prokaryotes
Cells making enzymes will have a lot of ribosomes
They consist of two subunits made in the nucleolus of the cell. The subunits are made separately and then moved to the cytosol for final assembly. The large and small subunits join together by binding an RNA strand.
Where are ribosomes located?
Attached to ER Attached to the nuclear envolope free floating in the cystosol In the mitochondrial matrix In the stroma of a chloroplast
peroxisome
AKA microbody
Membrane bound
contain over 40 oxidative enzymes
Catalase breaks down excess H2O2.
The peroxisome also creates H2O2. H2O2 detoxifies substances such as ethanol and even kills microorganisms.
Peroxisomes contain enzymes involved in lipid metabolism. It helps metabolize fatty acid chains of 18 carbons or longer. These fatty acids are made shorter and sent to the mitochondrial matrix for final beta oxidation.
Peroxisomes self replicate, but don’t have DNA like mitochondria, so they need their proteins transported in to start replication
Nucleolus
In addition to rRNA synthesis, the assembly of large and small ribosomal subunits occurs here.
Non-membrane bound organelle
one or more found in the nucleus. Rarely more than three.
Small amounts of DNA are present, but it doesn’t stain with a Feulgen stain.
In cancer cells the nucleolus is usually hypertrophic. You will also see large nucleoli in cells actively synthesizing a lot of proteins.
Nucleus
Largest organelle of the cell.
In a eukaryotic cell most of the DNA is found here.
It has a double membrane.
Inside the nucleus DNA is organized into units called chromosomes. The chromosomes are made up of protein and DNA called the chromatin complex.
Most cells are made up of 46 chromosomes. The gametes have 23.
Three main parts.
Nucleolus: rRNA synthesis
Chromatin: genetic material
Nucleoplasm: the content of the nucleus, excluding nucleolus
Most cells have one nucleus, but some cells have multiple and some cells have none.
Chromatin
made up of proteins and DNA
Heterochromatin: dark staining and much is found near the nuclear envelope. It is condensed and not actively transcribing.
Euchromatin: light area, less dense, less compact and has genes that are actively transcribing.
In most cells is there more euchromatin or heterochromatin?
Euchromatin is more abundant. Most of the DNA is actively transcribing.
What are some examples of multinucleated cells?
Osteoclasts (break down bone)
skeletal muscle cells
Liver cells often are
cancerous cells
What is an example of a cell that has no nucleus
Red blood cell
platelets
Proteosomes
Four stacked rings
These are small protein complexes about the size of a small ribosomal subunit.
They degrade denatured or unneeded proteins.
Lysosomes do the bulk of the job, but these focus on individual proteins. They remove abnormal or misfolded proteins using ATP to drive the needed conformational changes in their subunits.
What is inclusion?
Various nutrients or pigments that can be found within the cell, but do not have activity like other organelles.
Includes:
Pigments: melanin pigment in skin and hair
lipid droplets in fat cells
glycogen granules in liver and skeletal muscle cells.
Vacuoles: membrane bound vesicle more prominent in plants. They can be used for storage.
Crystals: likely remnants of certain processes.
Chloroplast
Site of photosynthesis
Inside are flattened sacs called thylakoids, a stack of sacks is called grana.
The fluid outside the thylakoids is called stroma. It contains DNA, ribosomes, and enzymes.
They have a double membrane.
Cyanobacteria
prokaryotic bacteria that produces O2 from CO2.
They contain chlorophyll and go through photosynthesis similar to plants
mainly found in water
Used to be called blue-green algae
unicellular
Cytoskeleton
Complex network of :
Microfilaments (actin)
microtubules
intermediate filaments
Determine the shape of the cell and play a role in the movement of organelles, vesicles, as well as the movement of the entire cell.
microtubules > intermediate filaments > microfilaments
Microtubules
involved with molecular motors, attaching to organelles and vesicles as well as chromosomes to help pull them apart.
Cilia and flagella are composed of microtubules
Strongest of all the cytoskeletal polymers.
What does colchicine do?
Mitotic poison. It disrupts the microtubules and halts mitosis. This halts the migration of white blood cells, which is responsible for inflamation.
It is used to treat gout.
What does Taxol do?
A drug used to treat ovarian and breast cancer. It binds to microtubules and prevents them from dissociating. It’s a way to stop mitosis.
What are the molecular motors of microtubules?
Dyneins and kinesins - Tow trucks of the cell. Pulling organelles and other parts of the cell along the microtubules.
Kinesins travel toward the plus end of the microtubule.
Dyneins travel toward the minus end of the microtubule
Microfilaments
Made up of actin
Uses myosin as its tow truck. Myosin walks along the microfilaments.
These are the major players of skeletal muscle contractions
Amoebas use actin and myosin to control their movement through pseudopodia.
cytoplasmic streaming is thought to be mediated by actin and myosin
Plays a critical role in phagocytosis and cytokinesis
What kind of pattern do flagella and cilia have. What structural monomer is it composed of.
Composed of microtubules in a 9 + 2 arrangement. The whole structure is called an axoneme.
Intermediate Fibers
Keratin is the predominant intermediate fiber.
More permanent fibers than microtubules or microfilaments
Anchor the nucleus in place and make up the framework for the entire nuclear envelope.
Provide much of the structure of the cell
Keratins
A predominant type of intermediate fiber.
A diverse family of over 20 types of proteins that provide protection against abrasion and prevent water loss in epidermal cells
Centrioles
FOUND ONLY IN ANIMAL CELLS, NOT PLANTS
Composed of 9 sets of microtubule triplets arranged in a cylinder with nothing in the middle. 9 + 0 (Different than the 9 sets + 2 of doublets in cilia and flagella with one in the middle(the +2) )
Centrosome
Centrosome - Most common microtubule organizing center (MTOC) within the cell.
A pair of centrioles and associated proteins comprise the centrosome. The centrioles are perpendicular to each other.
Before cell division, the centrosome replicates first. They then move to the opposite sides of the cell. Microtubules extend from the centriole to form the spindles that connect to the kinetochores on the chromosomes and help with mitosis.
Gap junction
Allows communication to occur between animal cells.
Connexins - Proteins around a pore control what can come in or out .
Very common in heart and muscle cells. (responsible for the heart’s coordinated beat)
Rapid exchange occurs between these junctions
Connexins
Proteins around a pore that control what can come in or out.
Plasmodesmata
intercellular channels that connect plant cells and some algal cells.
Similar in function to gap junctions in animal cells, but not the same structure. They traverse the cell wall
Tight junctions
Forms a tight seal that prevents anything from getting past the cells. (removes extracellular space between cells)
This forces solutes to pass through cells instead
Common in the cells of the GI tract.
Found in skin to keep us water tight.
Celiac disease
A disease where the tight junctions in the intestines don’t work properly and the intestines become leaky.
Desmosome
Think cell staples.
Fasten cells together into strong sheets.
Contain intermediate filaments which are very strong (keratin)
Common in epithelia that need to avoid abrasion (skin)
Pephigus vulgaris
auto-immune disease where the body attacks desmosomes. Resulting in blisters and possibly death.
Usually treatable with a steroidal agent.
