Cell Organelles Flashcards
Cell Structure Pic.
Blank on purpose.
Nucleus
- Largest organelle
- Two membranes form the nuclear envelope
- Contains the nucleolus
What is the nucleolus?
A small dense structure composed largely of:
- RNA
- Most of the cellular DNA;
- Histones: DNA binding proteins, that regulate its activity
Primary function of nucleus
The primary functions of the nucleus are
- Cell division and
- Control of genetic information.
Other functions include:
- Replication and repair of DNA
- Transcription of the information stored in DNA.
Discuss genetic information transcribed into RNA:
When genetic information is transcribed into RNA it can be processed into:
- Messenger
- Transport
- Ribosomal RNA
It is then introduced into the cytoplasm, where it directs cellular activities.
Where does most of the processing of RNA occur?
In the nucleolus
What represents about 1/2 the volume of a eukaryotic cell?
Cytosol
What is cytosol?
The aqueous solution in the cytoplasm that fills the cytoplasmic matrix.
- 55% of cell volume
Functions:
- Intermediary metabolism
- Enzymatic biochemical reactions
- Ribosomal protein synthesis
- Storage of:
- carbs,
- fat and
- secretory vesicles
What is the cytoplasmic matrix?
Space between the nuclear envelope and the plasma membrane.
What also functions as a storage unit for fat, carbohydrates, and secretory vesicles?
Cytosol
What are ribosomes?
- RNA-protein complexes (nucleoproteins) that are synthesized in the nucleolus and secreted into the cytoplasm through pores in the nuclear envelope called nuclear pore complexes (NPCs).
- may float free in the cytoplasm or
- attach themselves to the outer membranes of the endoplasmic reticulum
What is the chief function of ribosomes?
Provide sites for cellular protein synthesis
What is the endoplasmic reticulum (ER)?
- Membrane factory that specializes in the synthesis and transport of protein and lipid components
- Consists of network of tubular/saclike channels (cisternae) that extend throughout the cytoplams and are continuous with the outer nuclear membrane
What two characteristics can the folded membranes that form the cisternae of the endoplasmic reticulum be?
- Rough (granular)
- Smooth (agranular)
Why is rough ER (rER) rough?
Ribosomes and ribonucleoprotein particles are attached to it.
Why is smooth ER (sER) smooth?
It does not have ribosomes are ribonucleoproteins attached to i.
What is the chief function of the endoplasmic reticulum?
- Protein synthesis and folding.
- A new role is sensing cellular stress
- The endoplasmic reticulum communicates with the Golgi complex and interacts with other organelles, particularly lysosomes and peroxisomes.
What is the golgi complex?
- Network of flattened, smooth membranes and vesicles frequently located near the nucleus of the cell.
- Proteins from the endoplasmic reticulum are processed and packaged into small membrane-bound sacs or vesicles called secretory vesicles, which collect at the end of the membranous folds of the Golgi bodies—called cisternae.
- The secretory vesicles then break off from the Golgi complex and migrate to a variety of intracellular and extracellular destinations, including the plasma membrane.
- The vesicles fuse with the plasma membrane, and their contents are released from the cell.
What is the chief function of the golgi complex?
The Golgi complex is a refining
plant and directs traffic (e.g., protein, polynucleotide, polysaccharide molecules) in the cell.
What organelle do many molecules, including lipids, proteins, glycoproteins, and enzymes of lysosomes, pass through at some stage in their maturation?
Golgi Complex
What are the coats of best known vesicles from the golgi complex made of?
Coats made largely of the protein clathrin and are called clathrin-coated vesicles.
They bud from the Golgi complex on the outward secretory pathway and from the plasma membrane on the inward endocytotic pathway.
What are lysosomes?
- Lysosomes (lyso = dissolution; soma = body) are saclike structures that originate from the Golgi complex.
- They contain digestive enzymes called hydrolases,
What is the chief function of lysosomes?
- Lysosomes function as the intracellular digestive system
- Lysosomal enzymes are capable of digesting most cellular constituents completely to their basic components:
- such as amino acids,
- fatty acids, and
- carbohydrates.
Name one genetic defect affecting lysosomal storage:
Pompe Disease
Discuss Pompe Disease
- Glycogen accumulation in lysosomes
- Lack of:
- lysosomal a-1, 4-glucosidase
- Clinical Presentation:
- Predominant sign is usually progressive muscle weakness, generally beginning with the trunk and proximal muscles of the lower limbs.[1], [2]
- Clinical manifestations can first appear at any age, from early childhood to late adulthood.
- In children, the first signs may be delayed motor milestones.[
- Similarly, adults may first notice difficulty walking or climbing stairs and exhibit gait abnormalities.
- Early respiratory involvement resulting from degeneration of the diaphragm and other respiratory muscles may manifest as respiratory insufficiency, including orthopnea and indications of sleep-disordered breathing such as morning headaches and daytime fatigue.
- Feeding and swallowing difficulties
Poor weight gain/maintenance
What is Tay-Sachs disease?
- Lysosomal storage disease
- Accumulation of GM2 ganglioside (lipid) in lysosomes
- b/c of deficiency or absence of lysosomal hexosaminidase
- Inherited if both parents have Hex-a gene
- A defective gene on chromosome 15 (HEX-A) causes Tay-Sachs disease. This defective gene causes the body to not make a protein called hexosaminidase A. Without this protein, chemicals called gangliosides build up in nerve cells in the brain, destroying brain cells.
- Symptoms: muscle weakness, coordination issues, rhythmic muscle contractions, stiff muscles, faint feeling, dysphagia, hearing loss, seizures, vision loss and/or impaired voice.)
Brief discussion of gout’s patho:
- In gout, undigested uric acid accumulates within lysosomes, damaging the lysosomal membrane.
- Subsequent enzyme leakage results in cell death and tissue injury.
What are peroxisomes (microbodies)?
- Membrane-bound organelles that contain several oxidative enzymes such as catalase and urate oxidase.
- Peroxisomes contain enzymes that use oxygen to remove hydrogen atoms from specific substrates in an oxidative reaction that produces H2O2.
- Peroxisomes also have an important role in the synthesis of specialized phospholipids necessary for nerve cell myelination.
What are mitochondria?
- Mitochondria (mito = thread; chondros = granule), organelles
- Responsible for cellular respiration and energy production.
- Metabolic pathways involved in the metabolism of carbohydrates, lipids, and amino acids and special pathways involving urea and heme synthesis are located in the mitochondrial matrix.
- The outer membrane is permeable (passable) to many substances, but the inner membrane is highly selective and contains many transmembranous transport systems.
- The inner membrane contains a transporter to move electrically charged calcium (calcium ions).
- Mitochondria contain their own DNA that codes for enzymes needed for oxidative phosphorylation.
What is a vault?
An octagonal barrel-shaped organelle believed to transport messenger RNA from the nucleus to the cytoplasmic ribosomes.
What is the cytoskeleton?
- “bones and muscles” of the cell
- Maintains shape and internal organization
- Permits movement of substances within the cell and movement of external projections (cilia, flagella)
What is mechanotransduction?
Cellular process that translates mechanical stimuli into biochem signals, allowing to adapt to surroundings.
What is the plasma membrane?
Surrounds the cell or intracellular organelle.
Allow or exclude various molecules - selective transport allows for in/out molecule movement.
5 functions of cell membrane (PP)
- Structure
- Protection
- Activation
- Transport
- Cell to Cell interaction
Structure of phospholipid molecule
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Channel Receptor Example (Na/K pump)
Channel Receptors-Respond to receptor “stimuli”-transport proteins like channels from one side of membrane to anotherInactive and Active state
EXP: sodium-potassium ATPase -thousands in every membrane which
- use 1/2 of body’s energy every day
- shuttles 3 positive-charged sodium atoms out of the cytoplasm
- and simultaneously admits 2 positive-charged potassium atoms into the cytoplasm
- Each revolution throws off more + charges out of cell than it lets in leaving the cell negatively charged with outside cell positively charged creating a “membrane potential”
