Cell structure and function Flashcards
What is a cell?
A highly organised compartment bounded by a plasma membrane that contains concentrated chemicals in an aqueous solution
What does cell theory state?
That all organisms are made of cells and all cells come from preexisting cells
Who and when was the microscope invented?
Robert Hooke in 1665
Who was the first person to view an animal cell?
Anton van Leeuwenhoek
What is a genotype?
The sequence of bases in the DNA
What is the phenotype?
It is the produce of the proteins produced from the DNA
What are the universal similarities between cells?
- DNA is the heritable material (there is only 1 copy), RNA is the messenger and the product is the proteins
- Relationship between DNA, RNA and proteins (proteins formed from RNA, formed from DNA)
- Major cellular organelles
- ATP is the energy source
What is cytoplasm?
The material within a living cell excluding the cell nucleus within the plasma membrane
What is the cytoplasm made of?
Cytosol (aqueous of the cytoplasm of a cell) and the organelles and many small molecules, proteins and nuclei acids
What is plasma membrane?
Double layer of phospholipids with imbedded proteins
What is the phospholipid bi-layer made of?
A hydrophilic head and hydrophobic tails
What is the function of plasma membranes?
Physical barrier separating the inside and outside of the cell
Mediate movement of hydrophilic substances (it is semipermeable FYI)
Allows cell to cell identification
Facilitates intercellular communication
What is contact inhibition?
It is where cells grow until the plasma membranes come into contact with each other
When and what happens when contact inhibition doesn’t work?
Happens with cancerous cells and causes overgrowth
Where is most of the cholesterol made?
The liver
What is the function of cholesterol?
Holds the membranes together when the temperature increases and when the temperatures drops it maintains the fluidity of membrane (can increase/decrease fluidity of membrane based on cholesterol levels FYI)
What is phosphatidylcholine and phosphatidylserine?
- phospholipid on the outside of the cell
- phospholipid on the inside of the cell
What are the charges on the phospholipid and what impact does this have on its function?
Charged head makes it hydrophilic, non-charge tails makes it hydrophobic
What is the phospholipid head made of?
Choline head, phosphate middle and glycerol base
What are the phospholipid tails made of?
Fatty acids
What happens when a cell dies? Why is this process controlled?
It sends out a message to begin apoptosis where the phosphatidylcholine will flip (end up on the inside of the cell) and phosphatidylserine will go on the outside, this triggers exon 5 (???) which initiates the controlled dying of the cell so the it doesn’t impact neighbouring cells
What kind of proteins are imbedded within a plasma membrane?
Transmembrane protein, peripheral membrane protein, glycoproteins
What is the function of transmembrane proteins?
Contact extracellular and cytoplasmic environments
What is the function of glycoproteins?
Contribute ot eh molecular signature of the extracellular side of the cell
What are some of the functions of the plasma membrane proteins?
Transport, enzymatic activity, signal transduction, cell to cell recognition, intercellular joining, attachment to the cytoskeleton and ECM
What kind of protein controls transport over the plasma membrane?
Ion channels
What are the two kinds of ion channels? What are the differences?
Passive (no energy involved) and active (requires ATP)
What are and what do enzymatic activity proteins do in the membrane?
- Some enzymes sit imbedded in the plasma membrane
- provide a platform for cells to catalyse reactions, can be parts of a cascade of reactions
How does a signal transduction protein work?
A signalling molecule binds to the receptor protein which causes a signalling protein within the cell to be released
Do signalling molecules end up passing through the plasma membrane in order to activate the signal?
No, they just modify the signal transduction protein which releases a protein inside the cell
What kind of proteins are involved in cell to cell recognition?
Glycoproteins
What kind of protein/s is involved in intercellular connection?
Gap or tight junctions
What kind of proteins are involved in attachment to the cytoskeleton and ECM?
Integrins
What is a nucleus surrounded by?
A nuclear envelope made of lamina A
What is the function of the nucleus?
Stores DNA in eukaryotic cells, rRNA and ribosome producing, has spatial and temporal control the cell functions
How do things get in and out of the nucleus? What kind of things more in and out? Is it free flowing?
Through nuclear pores
RNA, some proteins, not free flowing controlled by enzymes
Is the nucleus a discrete organelle inside the cell?
No, it is continuous with rough endoplasmic reticulum
What is the nucleolus?
The centre of the nucleus
What is the function of the nucleolus?
site of rRNA production and assembles small and large subunits of ribosomes
What is DNA?
It is the nucleic acid that encodes our phenotype
What is epigenetic’s?
Small marks on the DNA laid down on the DNA by environmental factors
When and how can epigenetic’s impact an organisms phenotype?
From a gamete into adulthood
Rearranges how the histones are lined up impacting how proteins are produced
How are DNA stored? What is the structural organisation of the DNA as it prepares for cell division?
Wrapped twice around 8 histones to form a single nucleosomes (10nm) 3 nucleosomes form a chromatin.
These chromatin are condensed into chromatin fibres (30nm) which are further wrapped into loops (300nm) then stacked into 2 * chromosome (1400nm) held together by a centromere. These chromosome comprise of many genes
What is the monomer of DNA?
A nucleotide
What is a nucleotide made of?
Phosphate group, sugar (pentose) and nitrogen base
How are nucleotides held together?
By hydrogen and phosphodiester bonds
What are ribosome made of?
2 subunits, a small and large subunit
Where are the subunits for ribosome made?
In the nucleolus
Where can ribosome be found?
Free in the cytoplasm (makes cytosolic proteins FYI) or attached to rough ER
What is ER?
Extensive network of tubes and tubules stretching out form the nuclear membrane
What are the two types of ER?
Rough and smooth
What makes rough ER rough?
It is dotted with attached ribosomes
What does the rough ER do?
Fold the proteins formed by ribosomes in order to make them active and package them to be transported
What does the smooth ER do?
Is where lipids and carbohydrates are made, detoxify drugs or harmful substances, can do some modification of the proteins as well
Where is the smooth ER relative to rough ER?
extends form the rough ER
What is the function of the Golgi complex?
modifies, sorts, packages and transports proteins from the rough ER into the body
What is the structure of the golgi complex?
A number of flattened membranous sacs called cisternae stacked on top of each other, curved into a cup shape
What do cisternae do?
contain enzymes of different functions and the proteins move from cisternae sac to cisternae sac in order to modify them (e.g. folding) and packaging
What are the three stages of the golgi complex for processing proteins?
Entry cisternae receive proteins from rough ER
Medial cisterna odiar proteins for specific function
Exit cisterna modify further and package protein to necessary destination
What do lysosomes contain?
Hydrolytic and digestive enzymes
What are lysosomes made from?
Plasma membrane derived form golgi body
What happens when lysosomes burst?
Cell undergo apoptosis
What do the proteins in the plasma membrane of the lysosome do to make it an especially powerful digestive organelle?
Pump H+ into them
What is the function of the lysosome?
Digests substance that enter a cell, cell components (autophagy), entire cells (autolysis) and any extracellular digestion
What are the mechanisms and functions of autophagy?
Isolation membrane forms around cellular components for digestion which forms an autophagosome, These then dock and fuse with lysosome and the lysosome uses its digestive enzymes and acdis to break down cellular content
Breaks down material within the cell
What is the ‘power house’ of the cell?
Mitochondria
How many genes do mitochondria have, what do these genes code for? What is the likely origin of these organelles?
37 genes that code for rRNAs and tRNAs and mitochondrial components
Mitochondria are descend form purpose non-sulfur bacteria that survived endocytosis (therefore didn’t get broken up by lysosomes)
What does the number of mitochondria in a cell indicate?
The number of mitochondria of the cell determines the physical functions of the cell
What is the ATP cycle?
ATP undergoes hydrolysis losing a phosphate group releasing energy and producing energy, ADP and a phosphate group
What is the function of the cytoskeleton?
Maintain the size shape and integrity of the cell by acting as scaffolding across the cell, also involved in intracellular transportation and cellular movement
What are the three types of fibres in cytoskeletons?
Microfilaments, intermediate filmanets and microtubules
What is the structure of microfilaments?
Actin molecules assembled in two long chains twisted around each other, 7nm diameter
Where are microfilaments normally found?
Around the periphery and lining the interior of the cell
What is the function of the microfilaments?
Bear tension and weight by anchoring cytoskeleton to plasma membrane proteins
Are microfilaments permanent structures within the cell?
No, microfilaments are assembled and disassembled as required
What is the structure of the intermediate filament?
Diverse range of material, mainly keratin, diameter of 8-12nm
Where is the intermediate filament found?
In the cytoplasm
What is the function of the intermediate filaments?
Bear tension and weight throughout the cell and act as scaffold for other organelles
Are intermediate filaments normally permanent structures within the cell?
Yes
What is the structure of microtubule’s? What are they made of?
tubular structures made of tubular dimers alpha and beta that are coiled, 25nm diameter with central lumen of 15nm
Where are the two kinds of microtubule’s found?
Centrioles
Inside cilia
What is the function of the microtubules?
Support cell shape and size, guide movements of organelles, proteins and chromosomes (e.g. vesicles form golgi to membrane) and support movement of cilia
What are centrioles?
Organelles attached onto the nucleus involve in the formation of spindle fibres
What is different between the microtubules in the cilia and the centrioles?
Cilia microtubules have a basal plate, have a 9 + 2 rings
What does the 9 + 2 ring formation in the microtubules in the cilia allow it to do?
Allows for different microtubules to slide over each other which allows for bend so that the cilia can move therefore can disturb stuff in the external environment
Are microtubules normally permanent structures within the cell?
No, assembled and disassembled as required
