C5.1: Membrane-bound Flashcards
are cellular structures that are enclosed by a biological membrane, typically consisting of a single or double layer of lipids with interspersed proteins.
Membrane-bound organelles
Most of these organelles within cells are indeed filled with a fluid, and these organelles are enclosed by a ___ to create a distinct internal environment separated from the rest of the cytoplasm
plasma membrane
serve as physical barriers that enclose the contents of membrane-bound organelles, effectively isolating them from the surrounding cytoplasm.
Lipid bilayer membranes
are selectively permeable, meaning they control the passage of ions, molecules, and proteins in and out of organelles
Lipid bilayers
help establish and maintain distinct chemical environments within organelles
Membranes
help organize cellular processes by segregating enzymes, substrates, and reactants into specific compartments; this spatial organization enhances the efficiency and coordination of biochemical reactions.
Membranes
membrane-bound organelles (9)
Nucleus
Endoplasmic Reticulum
Mitochondria
Chloroplasts
Golgi Apparatus
Lysosomes
Peroxisomes
Secretory Vesicles
Vacuole
Function of ___ is the biosynthesis of ribosomal RNA and production of ribosomes
nucleolus
largets organelle; control center; regulate gene expression
Nucleus
site of cellular chemical reactions
ER
The ER is composed of a series of highly folded membranes called ___.
cisternae
Ribosomes are scattered across cisternae
Rough ER
___ are responsible for synthesizing polypeptides, which are subsequently either integrated into the membrane of the Rough Endoplasmic Reticulum (RER) or transported into the lumen, the central region, of the cisternae.
Ribosomes
it is where proteins are generated in the rough ER.
lumen of cisternae
Consist of interconnected membranous sacs without ribosomes; enzymes found either bound to the surface of this ER or situated within its cisternae.
Sooth ER
responsible for the transport of synthesized proteins; helps with the protein folding
Smooth ER
a process where sugar molecules are added to proteins or lipids.
Glycosylation-
double-membrane-bound, spherical or rod-shaped organelles
mitochondria
The term ‘mitochondrion’ is derived from the Greek words “___” and “___” which means “__” and “__”, respectively.
mitos (thread); chondrion (granules-like)
carry out oxidative phosphorylation; production of energy through ATP synthesis
Mitochondria
site for synthesizing food by the process of photosynthesis
chloroplast
Golgi apparatus is primarily made up of stacked, flattened pouches known as ___.
cisternae
Protein packaging and secretion; transportation; participate in the production of lysosomes
Golgi Apparatus
It digests dead and damaged cells, aids in digestion, and eliminates waste; “suicidal bags”
Lysosomes
are small organelles containing enzymes, primarily serve as the primary sites for intracellular digestion in cells.
Lysosome
Functions of lysosome (3)
Autophagy
Heterophagy
Biosynthesis
__: The digestion of cellular components and organelles from within the cell, allowing for recycling and the reuse of nutrients
Autophagy
: The digestion of external materials that are taken into the cell, such as nutrients acquired from the environment or particles ingested through processes like phagocytosis.
Heterophagy
: Involves recycling and processing unwanted or damaged cellular components and products of chemical reactions, contributing to the cell’s overall metabolic processes.
Biosynthesis
degradation of long-chain fatty acids by beta-oxidation; Breakdown of toxic compounds
Peroxisome
prominently associated with processes like fatty acid oxidation, detoxification of harmful compounds, and the synthesis of certain lipids called ___.
peroxisome; plasmalogens
involved in the transport and delivery of molecules like hormones or neurotransmitters, either into or out of the cell.
Secretory Vesicles
___ is the mechanism by which the contents of secretory vesicles are moved out of the cell. During this mechanism, these vesicles fuse with the cell membrane, releasing their contents into the extracellular space.
Exocytosis
__ is the process of moving the contents of secretory vesicles into the cell. This occurs when the cell membrane engulfs and internalizes external materials or molecules by forming vesicles.
Endocytosis
essential cellular structures found primarily in plant cells; maintaining turgor pressure or turgidity within the cell
Vacuole
results from the osmotic movement of water into the vacuole, causing the cell to become swollen and pushing the plasma membrane against the rigid cell wall.
Turgor pressure
Its structure consists of a network of interconnected membranous tubules, vesicles, and cisternae, which together form an extensive, intricate system throughout the cell.
ER
The endoplasmic reticulum (ER) is a vital
organelle in eukaryotic cells, responsible for a variety of cellular functions, including (4)
protein synthesis
lipid synthesis
calcium storage
detoxification
main function RER
protein synthesis
main function SER (3)
Lipid metabolism, detoxification, and calcium storage
Proteins destined for the Endoplasmic Reticulum (ER) are typically inserted into the ER
membrane ___
co-translationally
signal sequence is usually located at the __ of the
protein.
N-terminus
signal sequence is recognized by a complex called the ___
Signal Recognition Particle (SRP).
As proteins are synthesized on the ribosomes, they are modified and folded into their correct three-dimensional structure
PROTEIN PROCESSING
The ___also serves as a site for quality control in protein synthesis. It checks whether the synthesized proteins are correctly folded. Misfolded or improperly assembled proteins are targeted for degradation.
Rer
After their synthesis and processing in the RER, proteins are transported to their target destinations
TRANSPORT
Many proteins synthesized in the RER are ___, meaning they are destined for export out of the cell.
SECRETORY PROTEINS
___ is the process in which ribosomes in the cytoplasm or ER synthesize proteins
after the process of transcription of DNA to RNA in the cell’s nucleus. The entire process is called ____
Translation; gene expression
Translation proceeds in three phases
Initiation:
Elongation
Termination
The ribosome assembles around the target mRNA. The first tRNA is attached at the start codon.
Initiation:
The tRNA transfers an amino acid to the tRNA corresponding to the next codon. The ribosome then moves (translocates) to the next mRNA codon to continue the process, creating an amino acid chain.
Elongation:
When a peptidyl tRNA encounters a stop codon, then the ribosome folds the polypeptide into its final structure.
Termination:
Eukaryotes undergo translation in the cytosol or on the endoplasmic reticulum (ER)
membrane in a process known as __
co-translational translocation
During ____, the ribosome-mRNA complex attaches to the ER’s outer membrane, allowing newly synthesized proteins to enter the ER.
co-translational translocation
refers to the covalent and generally enzymatic
modification of proteins following protein biosynthesis
Post-translational modification (PTM)
Post-translational modifications can occur on the amino acid side chains or at the
protein’s ___
C- or N- termini
Attachment of lipid molecules, known as ___, often targets a protein or part of a protein attached to the cell membrane
lipidation
___ is one example that targets the modified protein for degradation and can
result in the formation of protein aggregates
Carbonylation
The SER is involved in ____, which encompasses the synthesis and modification of lipids
lipid metabolism
SER plays a pivotal role in breaking down ___ (foreign substances)
xenobiotics
One group of enzymes found in the SER, called ___, is particularly important in drug metabolism
cytochrome
P450 enzymes
there is an insufficient supply of oxygen in the cell, a condition known as __ ER may struggle to support oxygen-dependent processes.
Hypoxia
In cases of low glucose levels, ER may experience a shortage of energy
Hypoglycemia
High temperatures, can alter the chemical reactions taking place in the ER. Proteins may become denatured or misfolded due to excessive heat, leading to protein aggregation and ER stress.
Hyperthermia
acidic environment within the cell or ER can disrupt the normal pH balance required for enzymatic reactions and protein folding
Acidosis
Changes in calcium ion concentrations can disturb the ER’s calcium homeostasis and lead to disruptions in protein folding and transport
Calcium Ion Levels
refers to the balance between oxidized and reduced molecules within the cell, is crucial for various cellular processes, including protein folding
Redox State
often modulated by hypoxia and hypoglycemia, can compromise the ER’s ability to perform tasks such as protein synthesis and proper protein folding.
Reduced energy levels
FACTORS THAT CAN CONTRIBUTE TO ER STRESS (7)
-HYPOXIA
-HYPOGLYCEMIA
-HYPERTHERMIA
-Acidosis
-Changes in calcium ion levels
-Reduced energy levels
-ALTERED REDOX STATE
Cellular Response to ER Stress (4)
- Unfolded Protein Response (UPR)
- Proteotoxic Threat and Protein Clearance
- ER Lumen Dilation
- ER Stress Response
___ is a set of signaling pathways and cellular processes that aim to restore ER function and alleviate the stress. It involves a complex network of molecular events that are activated in response to the accumulation of unfolded or misfolded proteins within the ER lumen
UPR Unfolded Protein Response
damaged proteins are
exported from the ER to the cytoplasm and then targeted for degradation by the proteasome, a cellular protein disposal system
ER-associated degradation (ERAD),
damaged proteins are compacted together with other cellular debris into juxtanuclear complexes. These complexes are then recycled via autophagy, a cellular mechanism for the recycling of surplus or defective cellular components
aggresome formation
involves an expansion of the ER’s internal compartments, creating a larger lumen or internal space
ER Lumen Dilation
The primary purpose of this expansion is to accommodate the increasing load of proteins and other lumenal constituents that are being synthesized to manage ER stress.
ER Lumen Dilation
The ___ is a dynamic system that can lead to either adaptation or
apoptosis, depending on the severity of the stress and the cell’s ability to cope with it.
ER stress response
This module triggers a series of events that ultimately lead to cell death (apoptosis).
proapoptotic module
also known as microbodies; Made up of a phospholipid bilayer and crystalloid core which is not always present
peroxisome
While lysosomes break down proteins, peroxisomes break down fatty acids. Which is known as ___
lipid catabolism.
___ also known as free radicals like oxygen ions which is a byproduct of normal cellular respiration, radiation, tobacco, or drug
reactive Oxygen Species ROS molecules
Peroxisomes:
Metabolize chain of very long chain fatty acids via ___.
Metabolize branched chain of fatty acids via __.
beta-oxidation;
alpha-oxidation
___ is a myelin sheath that covers the nerve.
Plasmalogen
peroxisomes contain ___ that breaks down hydrogen peroxide into water and oxygen.
catalase
Peroxisomal disorder that is Autosomal recessive, both parents are carriers of the gene, specifically the gene called PEX gene.
Zellweger Syndrome
___ is important because it codes for proteins called peroxins that are essential in making peroxisomes.
PEX gene
In order for a protein to get into the peroxisome, it needs to have a targeting signal called the ___
peroxisomal targeting signal
Types of Protein Targeting Signals in peroxisome (3)
-PTS1
-PTS2
-PMP
- takes protein in the lumen of the peroxisome
PTS1
- helps protein to get integrated inside the membrane of the peroxisome
PMP
Zellweger’s syndrome is caused by mutations in any of 13 of the 14 PEX genes, mostly in ___
PEX1
