Eukaryotic cell structure Flashcards
What is the function of the eukaryotic organelles?
They provide specialised environments.
Facilitate processes with different chemical requirements
How do the organelles work?
They cooperate (protein trafficking) or act autonomously to accomplish a given function
How many compartments in an organelle?
An organelle has one or more compartments
What are the main eukaryotic organelles?
Cytoplasm/cytosol
Mitochondria
Lysosomes
Describe cytoplasm as an organelle
- cytoplasm = area contained by the plasma membrane+ everything excluding the nucleus
- contains many membrane bound compartments (these membrane facilitate distinct environments within the organelle)
Cytosol definition and composition and function
- cytosol=largest compartment of the cell
- composition: aqueous gel, densely packed molecules
- function –> site of many chemical reactions: EARLY STEPS IN NUTREINTS BREAK DOWN, ATP GENERATION (ANAEROIC GLYCOLYSIS), MANUFACTURING OF PROTEINS, SIGNAL TRANSDUCTION
MITOCHONDRIA
- where is it present
- structure
- Present in all eukaryotic cells
- function: cellular respiration (pyruvate oxidation) ; Mitochondria play an important role in cell death mechanisms
- STRUCTURE: cylinders reassembling bacteria, exhibit high degree of plasticity and movement. Mitochondria remain fixed in some cells associated at sites requiring most energy
How many mitochondria present in a cell?
- Number of mitochondria can vary within a cell and between cell type
- Liver ~1000-2000/cell; 20% cell volume
- Numbers can increase in muscle cells
What are the components of mitochondria?
- outer membrane
- intermembrane space
- inner membrane
- matrix
Function and structure of outer membrane in mitochondria
- separation of external and internal environments
- role in cell death (disruption of outer membrane allows proteins from intermembrane space to leak into cytosol )
- structure: similar to plasma membrane
Function and structure of intermembrane space in mitochondria
- contains cytochrome C: essential component of the electron transport chain as it carries an electron
- Function: Important in apoptosis, Cytochrome C release from mitochondria into cytosol induces a series of biochemical reactions that result in cell death
Inner membrane in mitochondria: structure and function
- STRUCTURE: Highly folded to form cristae –> Increase surface area of inner membrane (5x vs. outer membrane)–> enhance ability to produce ATP
- Mitochondria of cells with high ATP demand contain more cristae c.f. typical mitochondria (EG MUSCLE CELLS VS SKIN CELLS)
Structure and function of matrix in mitochondria
- Contains most of mitochondrial proteins/enzymes (Pyruvate and fatty acid oxidation, citric acid cycle)
- contains mitochondrial ribosomes, tRNA and mtDNA and several copies of the mitochondrial genome
- 37 total genes that encode: tRNA and rRNA and Inner membrane proteins
Lysosomes
- what are they?
- structure
- where are they produced from?
- Principal sites of intracellular digestion
- Produced from Golgi
- Contain many hydrolytic enzyme (lipases, Carbohydrases, Nucleases, Proteases )
- pH dependent activity
Function of lysosomes
- digest macromolecules from: phagocytosis (external pathogens); endocytosis (receptor recycling); autophagy (excess/old organelles)
- specialised environment for enzyme function
Phagocytosis definition
- Phagocytosis is a specific form of endocytosis by which cells internalise solid matter, including microbial pathogens.
- Phagocytes of the immune system include macrophages, neutrophils and dendritic cells
Endocytosis definition
Endocytosis is uptake of macromolecules and particles from the surrounding medium. Internalized material is surrounded by an area of plasma membrane, that form a vesicle
Autophagy definition
Autophagy is an intracellular degradation system that delivers (dysfunctional) cytoplasmic components to the lysosome
Endsomes definition
-endosomes= membrane bound organelles that sort and deliver internalised material from cell surface
Process of formation of endocytotic vesicles
- plasma membrane buds inwards –> plasma membrane pinches off to form intracellular endocytotic vesicle
- can fuse with lysosomes and be recycled at the surface
Exocytosis definition
=counterpart of endocytosis
-a form of active transport; molecules (such as proteins) are transported out of the cell or receptors are inserted into the cell membrane
Function of endosomes
- internalisation of nutrients
- regulation of cell surface protein expression
- uptake and digestion of extracellular debris
- can be exploited by pathogens
Which organisms depend on endocytic uptake?
- most viruses depend on endocytic uptake, vesicular transport through the cytoplasm
Why do cells require endocytosis?
-most molecules required for cell function are large, polar that can’t pass through the hydrophobic portion of the plasma cell membrane by passive means