Lecture 5 Flashcards
Internal membranes
eukaryotic cells have internal membranes that compartmentalise their functions
What are the cells advantage of having organelle?
- cells compartmentalise chemistry
-concentration= number of molecules in a given volume
-so if we reduce the volume we increase the concentration and the probability of a chemical reaction occurring
Cytosol
the intracellular fluid that is present inside the cells
made up of water ions small molecules and proteins
site of all metabolic chemical reactions of prokaryotes
the fluid without any organelle
Cytoplasm
the part of the cell that is contained within the entire cell membrane
made up of water, nucleic acids, enzymes, lipids, amino acids and carbohydrates
site of large scale cellular activities including glycolysis and cell division
the jelly-like substance together with the organelle
Plasma membranes
the plasma membrane is a selective barrier that allows sufficient passage of oxygen nutrients and waste
the general structure is a double layer of phospholipids
structure of plasma membrane
outer hydrophilic region and inner hydrophobic region
surface area:volume ratio is critical
relationships between surface area and volume
a large surface area to volume ratio makes it much easier faster to exchange materials
larger organisms don’t have bigger cells they have more small cells
purpose of cell compartment
they can provide different local environments that facilitate specific metabolic functions
so many different functions can occur at the same time
Components of the endomembrane system
nuclear envelope
endoplasmic reticulum
Golgi apparatus
lysosomes
vesicles and vacuoles
plasma membranes
The main functions of the endomembrane system are
synthesis of proteins
transport of protein into membranes or out of the cell
metabolism and movement of lipids
detoxification of poisons
Protein synthesis in endomembrane system
proteins made by ribosomes on surface of ER and are threaded into the ER cavity through a pore in the membrane
the secretory proteins depart from the ER in membrane-bound vesicles
Rough ER
proteins
make enzyme responsible for producing membranes
Endoplasmic reticulum
accounts for more than half of the total membrane in many cells
can be rough (with ribosomes) or smooth
Functions of RER
has bound ribosomes, which make glycoproteins
distribute transport vesicles
ribosomes
protein factories
complexes made of ribosomal RNA and proteins
ribosomes carry out protein synthesis in the cytoplasm or on the RER
proteins made by free ribosomes are used in the cell and bound ribosomes are secreted
Smooth endoplasmic reticulum
synthesises lipids
metabolises carbohydrates
detoxifies
stores calcium
enzymes in the smooth ER produce lipids
Golgi apparatus
shipping and receiving centre
consist of flattened membranous sacs called cisternae
functions of Golgi apparatus
modifies products of the ER
manufactures certain macromolecules
sorts and packages materials into transport vesicles
vesicles come from ER into cis side and pass through cisternae to trans side before being sent to various destination
also manufactures macromolecules in plant cells
molecular identification tags are added in the Golgi to help target protein products to the correct cell
Faces of the golgi apparatus
cis- the receiving side
trans- shipping side of the Golgi apparatus
Lysosomes
digestive components
a membrane sac of hydrolytic enzymes that can digest macromolecules
enzymes made by rough ER
bound off Golgi trans face as a vesicle
lysosome functions
to engulf potentially harmful bacteria or viruses
take in food for the cell to use
recycle old or worn out organelle
peroxisomes
specialised metabolic compartment
contains enzymes that remove H atoms from various substances and transfer them to o2 to form H2O2
some peroxides breakdown fatty acids for cellular respiration, others detoxify alcohols
H2O2 is also toxic but peroxisomes contain an enzyme to turn it to water
vacuoles
large vesicles formed by fusion of smaller vesicles
the solution inside is different to cytosol
contains cell sap in plant cells
helps to maintain pressure in plant cells
function of vacuoles
In plant- contain water allowing structural support due to increased pressure + pushed chloroplasts closer to the light
In animals- mainly important in phagocytosis
