Session 2: Characteristics, structure & functions of a cell Flashcards
Define membranous and non-membranous organelles and give examples.
Membranous organelles: organelles that are surrounded by a plasmamembrane and are isolated from the cytosol, e.g mitochondria
Non-membranous organelles: organelles that are not surrounded by a plasmamembrane and are in direct contact w/ cytosol, e.g ribosomes, microtubuli
List the different cytoplasmic organelles that occur and state the function of each.
Endoplasmic Reticulum: contain large amounts of protein
Golgi apparatus: transported substances from the ER are processed to form lysosomes, transport vesicles, etc.
Lysosomes: serve as the intracellular digestive system
Peroxisomes: oxidizes substances that might be poisonous to the cell
Secretory vesicles: store protein proenzymes
Mitochondria: powerhouse of the cell
Cytoskeleton( filament and tubular structures): provides rigid, physical structures for certain parts of the cell
Nucleus: control centre of the cell
Nuclear membrane: large complexes of protein molecules attached at the edges of the pores
Nucleolus: some synthesised RNA is stored
List the different cytoplasmic organelles that occur and state the function of each.
Endoplasmic Reticulum: contain large amounts of protein
Golgi apparatus: transported substances from the ER are processed to form lysosomes, transport vesicles, etc.
Lysosomes: serve as the intracellular digestive system
Peroxisomes: oxidizes substances that might be poisonous to the cell
Secretory vesicles: store protein proenzymes
Mitochondria: powerhouse of the cell
Cytoskeleton( filament and tubular structures): provides rigid, physical structures for certain parts of the cell
Nucleus: control centre of the cell
Nuclear membrane: large complexes of protein molecules attached at the edges of the pores
Nucleolus: some synthesised RNA is stored here
Describe the structure of a cell membrane.
- Double layer of phospholipid molecules
- Cholesterol
- Integral and peripheral proteins
- Contains lipids, carbohydrates and functional proteins
What are the 4 functions of the cell membrane?
- Physical isolation - acts as a barrier
- Regulates exchange with the external environment - diffusion, osmosis, phagocytosis
- Monitors the environment - extracellular fluid composition & chemical signals
- Structural support - anchors cells and tissues
Explain the 4 steps of endocytosis.
- Receptors accumulate on the cell membrane
- Receptors bind to target molecules
- Target molecules form vesicle-like invagination on plasmamembrane
- Proteins and receptors are pulled into the forming vesicle
Explain exocytosis
Substances (proteins and receptors) exit the cell
What is the functional role of endosomes in a cell?
Sort and recycle proteins internalized by endocytosis
Describe the 3 functions of lysosomes?
- Intracellular digestion
* break down molecules
* attack bacteria
* recycle basic components of broken down damaged
organelles
* ejects waste by exocytosis - Autolysis of tissue
- Defends the body against certain bacterial invaders
Define the term primary lysosome.
Formed by Golgi and inactive enzymes
Define the term secondary lysosome.
- Lysosome fused with phagosome or damaged organelle
- Digestive enzymes activated
- Toxic chemicals isolated
Define the term residual body.
Vesicles containing indigestible material
Define autophagy.
Processs that maintains normal functioning of the cell by protein degradation and turnover of the dstroyed cell organelles for new cell formation.
Define heterophagy.
Digestion of a substance in the cell’s environment through pinocytosis or phagocytosis.
What is the function of the rough-surfaced endoplasmic reticulum?
Exporting in protein synthesis
In what type of cells would the rER be well-developed and why?
…
What are the 9 functions of the smooth-surfaced endoplasmic reticulum?
- Absorbed fatty acids are resynthesized
- Transcellular transport of fats
- Lipoprotein synthesis
- Role in muscle contraction
- Secretion of Cl- ions
- Synthesie steroid hormones
- Oxidation to detoxify poisonous substances
- Break down of glycogen
- Triglyceride synthesis
What are the functions of the
- Connected w/ protein production
- Protein undergo changes in sacculae
- Produce secretory vesicles, enzymes, hormones
- Add carbohydrates to proteins (glycoproteins)
Describe the basic structure of mitochondria.
- Have smooth outer membrane and folded inner membrane(cristae)
- Matrix around the cristae
What are the functions of mitochondria?
Produces energy needed for the functioning and survival of the cell by:
- houses the chains of enzymes responsible for cell respiration
- require O2 & organic substrates
- generate CO2 & ATP
What are the 4 functions of peroxisomes?
- Breaks down fatty acids and organic compounds
- Contains oxidases and regulates H2O2 levels
- Site of urate oxidase
- Possibly responsible for gluconeogenesis
What is the function of microtubules?
- Attach to the centrosome
- Anchor organelles and strengthen cells
- Change cell shape
- Move vesicles within the cell
- Form spindle apparatus
What are the structural differences between basal bodies and centrioles?
A centriole is surrounded by cytoplasm AND basal bodies have no cytoplasm surrounding it
Describe the 4 pathways for the ingestion of particles by a cell.
- Diffusion- substances move thru cell membrane pores
- Active transport- actual carrying of substances by a physical protein structure that penetrates all the way thru the mebrane
- Pinocytosis- ingestion of minute particles that form vesicles of ECF
- Phagocytosis- ingestion of large particles
Describe the pathway for the digestion of particles by a cell.
- Lysosomes attach to the vesicle
- A digestive vesicle is formed inside the cytoplasm
- The proteins, carbs, lipids, etc are hydrolyzed
Describe the pathway of secretion of particles by a cell.
The residual body with indigestible substances is excreted externally through exocytosis.
Describe the synthesis and secretion of proteins by a cell.
- Proteins are synthesized by ribosomes
* Synthesized proteins are extruded to the cytosol by ribosomes
Describe the pathway for the synthesis of proteins for intracellular use.
Some synthesized proteins are extruded to the ER by ribosomes into the endoplasmic matrix.
Define autodigestion.
The digestion of tissue by enzymes produced by the organism itself.
Explain the various ways of passage through the cell membrane.
- Diffusion
- Active transport
- Phagocytosis
- Pinocytosis
