Session 2 - General Characteristics, Structure And Function Of A Cell Flashcards
What are membranous organelles?
Cell organelle that are surrounded with a plasma membrane are isolate from the cytosol.
Give 5 examples of membranous organelles.
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Glogi apparatus
Endosomes
Mitochondria
What are non-membranous organelles?
Cell organelles that have no plasma membrane and are in direct contact with the cytosol.
What are the functions of the cell membrane?
- Physical isolation
- Regulates exchange with environment - ions and nutrients enter and waste and cellular products are released through diffusion, osmosis, active transport and phagocytosis.
- Monitors the environment - the extracellular fluid composition and chemical signals
- Structural support - anchors cells and tissues
Explain the mosaic model of the cell membrane.
It is about 8,5 -10 nanometers in cross section and has a double layer of phospholipid molecules. The majority of the lipid molecules are cholesterol. The cell membrane also contains integral and peripheral proteins as well as carbohydrates.
List the 6 membrane proteins are explain their functions.
- Structural proteins - junctions with neighbouring cells
- Linkers - anchor intracellular skeleton to extracellular matrix
- Enzymes - catalyse reactions
- Receptor proteins - bind and respond to ligands (ions and hormones)
- Carrier proteins - transport specific solutes through the membrane
- Channels - regulate water flow and solutes through the membrane
What is endocytosis?
A type of vesicular transport that used ATP to transport objects into the cell.
What is exocytosis?
A type of vesicular transport that uses ATP to transport objects out of the cell.
What are the categories of cellular transport?
- Diffusion
- Carrier-mediated transport
- Vesicular transport
What happens during phagocytosis?
Pseudopodia engulf large objects in phagosomes and transport them into through the cell membrane.
What is the function of endosomes?
They sort and recycle protein internalised by endocytosis.
What is the function of the rough endoplasmic reticulum?
Protein synthesis
What are the functions of the smooth endoplasmic reticulum?
- Synthesises steroid hormones
- Responsible for the oxidation, conjugation and methylating process to neutralise certain hormones and detoxify poisonous substances.
- Involved in metabolism (breaking down) of glycogen
- Synthesises triglyceride
- Resynthesises absorbed fatty acids and glycerol to form neutral fats
- Plays a role in muscle contraction by concentrating and releasing calcium 2+ ions.
What are the functions of the glogi apparatus?
- Involved in protein production as proteins undergo changes in the sacculae.
- Produces secretory vesicles, enzymes or hormones
- Adds carbohydrates to proteins - glycoproteins
What are the functions of the lysosome?
- Breaking down large molecules
- Attack bacteria
- Recycling basic components of broken down damaged organelles
- Ejecting waste products by exocytosis
- Autolysis/post-mortem degeneration of tissues
- Defend the body against certain bacterial invaders
What is the function of peroxisomes?
- They contain oxidases which regulate H2O2 levels
- They break down fatty acids and organic compounds
- Possibly responsible for gluconeogenesis
What are the functions of mitochondria?
They provide most of the energy required for the cell:
- Houses the chains of enzymes responsible for what is termed cell respiration
Give 4 examples of non-membranous organelles.
- Microtubuli
- Actin filaments
- Intermediate filaments
- Ribosomes
What are the functions of microtubules?
attach to the centrosome
strengthen the cell and anchor organelles
change the shape of the cell
move vesicles within the cell
form spindle apparatus
What is the function of cilia?
They move fluids across the cell surface
What is the structure of cilia?
They are composed of 9 peripheral duplets of microtubuli and 2 central microtubuli
Where are basal bodies located?
At the base of cilia
What is the structure of basal bodies?
They are composed of 9 peripheral triplets pf microtubuli.
What are the functions of actin filaments?
Provide additional mechanical strength and interact with proteins for consistency.
Pair with thick filaments of myosin for muscle movement
What are the functions of intermediate filaments?
- Strengthen the cell and maintain shape.
- Stabilise organelles
- Stabilise cell position
What is the function of the nucleus?
It is the control centre of the cell
What are the components of the nucleus?
- Chromatin
- Nucleolus
- Nuclear envelope which contains nuclear pores
- Nucleoplasm
Describe the structure of a chromosome from DNA until chromosome.
The double helix DNA strand coils around nucleosomes. The strand of nucleosomes coils to form chromatin fiber. The chromatin fibers form loops with domains and are anchored in non-histone protein and these then form a chromosome.
What are cytoplasmic inclusions?
Non-living intracellular substances that are not bound by any membrane and do not carry out any metabolic activity
Which cell structures contain microtubules?
- MTOC
- Centrioles
- Basal bodies
- Cilia
- Flagella
- Mitotic spindle
What is the function of ribosomes?
Synthesise proteins for maintenance of the cell
What is autophagy?
Autophagy is a housekeeping process whereby obsolete organelles and large protein aggregates are degraded and recycled.
What is heterophagy?
when a cell ingest/phagocytose a substance from outside of the cell, into the cell. This substance is then digested within the cell.
In which types of cells would the rough endoplasmic reticulum be well developed?
The rER will be well developed in all cells that produce large amounts of protein for export.
Hepatocytes (liver cells) – secrete various proteins including albumin,…
Mamary gland secretory cells – secrete milk protein.
Salivary gland secretory cells – secrete enzymes in saliva (proteins).
