Cell Structure and Function
What are the four factors that determine structure and function?
Matter, energy, organization, and information
What is the cytosol?
The region of a eukaryotic cell that is outside the organelles but inside the plasma membrane - it is a central coordinating region for many metabolic activities of eukaryotic cells
What is the endomembrane system?
A large network of membranes that enclose the nucleus. It includes the nuclear envelope, endoplasmic reticulum, golgi apparatus, lysosomes, vacuoles, and peroxisomes
Where do proteins involved in ATP synthesis originate from?
Made in the cytosol and taken into mitochondria.
What are the internal structures of a chloroplast?
Inner membrane, thylakoid membrane, thylakoid lumen, granum, and stroma.
What is the plasma membrane made out of?
Double-layer of phospholipids and embedded protein
What is catabolism vs anabolism?
Catabolism: the breakdown of a molecule into smaller components - needed by the cell to utilize energy and to generate molecules that provide building blocks to construct macromolecules
Anabolism: synthesis of molecules and macromolecules - ex: polysaccharides are made by linking sugar molecules
What are nuclear pores?
They provide a passageway for the movement of molecules and macromolecules into and out of the nucleus. They are formed where the inner and outer nuclear membranes make contact with each other
What are the functions of the protein- RNA complex SRP?
Recognizes the ER signal sequence and pauses translation.
Binds to the SRP receptor in the ER membrane docking the ribosome over a channel.
How do mitochondria make ATP?
They convert chemical energy stored within bonds into energy by breaking down covalent bonds in sugars, fats, and amino acids into simpler molecules. This releases energy used to make ATP.
What is the difference between prokaryotes and eukaryotes?
Prokaryotes lack a membrane-enclosed nucleus and hold genetic material in the nucleoid, also secrete glycolax
Where is the cytoskeleton found?
Primarily in the cytosol and also in the nucleus along the inner nuclear membrane
What is the difference between rough ER and smooth ER?
Rough ER: studded with ribosomes and sorts proteins that are destined for the ER, golgi apparatus, lysosomes, vauoles, plasma membrane, or extracellular environment. The proteins are packaged into membrane vesicles and the ER helps attach carbohydrates to proteins and lipids via glycosylation.
Smooth ER: lacks ribosomes and has three main functions: metabolism, storage of Calcium ions, and lipid synthesis and modification
What is the role of chaperone proteins in post translational sorting?
The chaperones keep the protein in an unfolded state when in the mitochondrial matrix which allows it to be transferred to a channel in the outer mitochondrial membrane.
What is the difference between the genomes of mitochondria and chloroplasts and the genome of the nucleus?
Genomes of mitochondria and chloroplasts are made of singular circular chromosomes but they may each contain multiple copies. Nuclear DNA is much longer and consists of 46 chromosomes.
What structures are found in plant cells but not animal cells?
Chloroplasts, a central vacuole, and a cell wall
What are motor proteins?
A category of proteins that use ATP as a source of energy to promote various types of movements. The hinge and tail make up the lever arm, and the head is the site where ATP binds and is hydrolyzed to ADP. To cause movement, the head region interacts with a cytoskeletal filament. They can cause three types of movement: movement of cargo via the motor protein, movement of the filament, or bending of the filament.
What is the role of lysosomes?
Break down molecules and macromolecules. They digest substances that are taken up from outside the cell via endocytosis, and also break down intracellular molecules and macromolecules to recycle their building blocks in the process of autophagy
What is the ER signal sequence and what does it contain?
The ER signal sequence directs a polypeptide to the rough ER membrane. It is a sequence of 6-12 hydrophobic amino acids. As the ribosome makes the polypeptide this sequence emerges and is recognized by the SRP.
What discovery allowed for the adoption of endosymbiosis as the origin of mitochondria and chloroplasts?
The discovery that these organelles contain their own genetic material.
What is liquid-liquid phase separation?
Aggregated solutes, such as proteins and RNA molecules, separate from the bulk solvent and form a droplet- molecules can diffuse within the droplet and occasionally leave it and pass into the surrounding liquid phase
What is the difference between microtubules, intermediate filaments, and actin filaments?
Microtubules: long, hollow, cylindrical structures- have a plus and minus end, and has dynamic instability. They help sort chromosomes during cell division and grow from centrosomes in animal cells. Important for cell shape and organization and are involved in the organization and movement of chromosomes during mitosis and in the orientation of cells during cell division
Intermediate Filaments: bind in a staggered array to form a twisted, ropelike structure- tension-bearing fibers that maintain cell shape and rigidity. Have permanent length and can line the inner nuclear membrane and provide anchor points for the nuclear pores.
Actin Filaments: thinnest filaments, plus and minus ends, dynamic structures, spiral around each other. They play a key role in cell shape and strength and are highly concentrated near the plasma membrane. They support the P.M. and provide shape and strength to the cell. They are anchored to other proteins near the plasma membrane
What are the models of the Golgi apparatus?
Vesicular transport model: materials are transported between the golgi cisternae via membrane vesicles that bud from one compartment in the Golgi and fuse with another compartment
Cisternal maturation model: vesicles from the ER fuse to form a cisterna at the cis face; the cisterna that was previously at the cis face becomes a medial cisterna. This addition of a cisterna moves the other medial cisternae toward the trans face. A cisterna at the trans face is lost as a result of the export of vesicles from its surface
What is the difference between cotranslational sorting and post-translational sorting?
Co-tranlational sorting is the synthesis of proteins beginning in cytosol and halting temporarily until ribosome attaches to ER membrane while post-translational is uptake of proteins into nucleus, mitochondria, chloroplasts, or peroxisomes occurring after protein is completely translated.
Why do mitochondria and chloroplasts need to divide?
They divide in order to maintain these organelles when a cell divides and grows. Environmental conditions also influence the numbers of these organelles so if plants are exposed to more sunlight, the number of chloroplasts increases.