SESSION 1 Flashcards
Define Golgi body
Export of proteins
Detoxification reactions
Relieves proteins/ lipids from RER Modifies, sorts and packs into vesicles Dispatched to one of three destinations: 1) within the cell to lysosomes 2) plasma membrane 3) outside cell
Cis Golgi network- the entry area of the Golgi
Trans Golgi network- final reactions and sorting takes place
Define Cytoplasm
Metabolism of carbohydrates, amino acids and nucleotides
- fatty acid synthesis
Define Lysosomes and their functions
Cellular digestion
Functions:
- release enzymes outside of the cell (exocytosis)
- digestion of materials from inside the cell (autophagy)
- digestion of materials from outside the cell
(Heterophagy)
- recycle products of biochemical reactions - materials brought back into the cell (endocytosis)
- completely break down cells that have died (autolysis)
Define mitochondria
ATP synthesis by oxidative phosphorylation
Mitochondria contain their own genetic information that can divided- maternal linage
Double membrane
Inner membrane folded into cristae
Define endoplasmic reticulum
Export of proteins
- membrane synthesis
- lipid and steroid synthesis
- detoxification reactions
- protein synthesis (RER)
Define nucleus
DNA synthesis and repair
Define nucleolus
RNA processing and ribosome assembly
Define plasma membrane
Cell morphology and movement
- transport of ions and small molecules
Define ribosome
Protein synthesis
List the principal differences between prokaryotic and eukaryotic cell
Prokaryotic cells lack a nucleus and other membrane bound organelles, other than a ribosome
Consists of one circular strand of DNA
Their cytoskeleton is flagella only
They also have a cell wall
How can the differences in prokaryotic and eukaryotic cell structure and function be exploited by medicine?
The cell wall can be targeted by drugs such as antibiotics, which will not affect eukaryotic cells in the same way
Discuss the bonds important for macromolecular structure and interaction
Monomeric units are joined together by covalent bonds to form macromolecules
Macromolecules are held together by non- covalent interactions:
- hydrogen bonds: from between a hydrogen atom bound to an electronegative atom and another electronegative atom
- ionic interactions- can be attraction of repulsion depending on barge
- hydrophobic interactions: non- polar. Won’t interact with water, e.g. Lipids. Good for storage, bilayer
- van der waals interactions: any two atoms in close proximity
Explain the difference between hydrophobic and hydrophilic molecules
Hydrophobic- will not interact with water, e.g. Lipids, storage without water and can pass through lipid bilayers
Hydrophilic- polar, interact with water. Reduces storage ability (e.g. Glycogen)cannot pass through lipid bilayers unassisted
Explain what is meant by amphipathic
How can these molecules form a lipid bilayer?
It has both hydrophobic and hydrophilic parts on the same molecule
When immersed in water, they arrange themselves so hydrophilic heads are exposed and hydrophobic tails are contained internally
Explain the concept of pH, pK and buffers
PH:
A measurement of the concentration of H+ ions in a solution.
- strong acids and bases completely dissociate in solution
- weak acids and bases barely dissociate
PK:
The stronger the tendency of an acid to dissociate the lower the pKa value
Buffers:
Mixtures of a weak acid and its conjugate base which resist changes in pH
When pH> pK the deprotonated dominates
When pH < pK the protonated form dominates
When pH = pK the amount of acid and its conjugate base is equal
How do you calculate the concentration of H+ ?
PH= -log[H+]
H+ = 10^-pH
Classify amino acids according to the properties of their R groups
AA’s can be classified by:
- their interaction with water at a pH of 7
- the charges of their side chains at a pH of 7
AA’s with benzene rigs are described as aromatic, without are aliphatic
Nonpolar, aliphatic/ polar, uncharged/ aromatic/ positively charged/ negatively charged
Explain how the charge on amino acids are affected by pH
A zwitterion is a neutral molecule that has both positive and negative charge
When pH > pKa of an AA, it becomes deprotonated and vice versa
Explain how AA charge can influence the isoelectric point of a protein
PI- the isoelectric point is the pH at which the protein has no overall charge
Acidic proteins (low pH) contain many negatively charged amino acids and have a low pI Basic proteins (high pH) contain many positively charged amino acids and have a high pI
Why do metabolically active tissues cause a fall in blood pH?
During metabolic activity many acidic byproducts, e.g. Lactic and carbonic acid, are produced lowering pH
This is true of aerobic as well as anaerobic conditions
Explain how a peptide bond is formed and list its key features
- AA’s are covalently bound to one another via a peptide bond that forms between the carboxyl group of one AA and he amino group of a second
- peptide bond formation is a condensation reaction - releases H2O
- all atoms of the bond are in the same plane
- there is no rotation about the peptide bond due to double bond characteristics
- carbonyl oxygen and aside hydrogen are in the trans orientation
Explain how rapid breathing ((hyperventilation) can cause an increase in blood pH
More CO2 is lost
Decrease in carbonic acid
Therefore there is an increase in pH as there is less acid
What effect would a pulmonary obstruction have on blood pH?
A pulmonary obstruction would decrease the pH as there is a build up of CO2
Explain how DNA is packaged
147 base pairs of DNA is wrapped around 8 histones to form the basic chromatin unit- the nucleosome
Looped further into a structure called a solenoid
Coiled again into a tightly packed structure- chromosome
What is the role of chromatin?
Allows mitosis and meiosis
Prevents chromosome breakage
Controls gene expression
Controls DNA replication
Define euchromatin
chromosome material which does not stain strongly
Define heterochromatin
chromosome material of different density from normal - stains darker
Define fluid mosaic model
Lipid bilayer
Proteins embedded in the bilayer
What are the functions of the plasma membrane?
- selective permeability
- transport of materials along cell surface
- endocytosis
- exocytosis
- intracellular adhesion
- intercellular recognition
- signal transduction
Define glycocalyx
Give examples within the body
A thick, sticky outer covering of the plasma membrane
Composed of strand of sugars and proteins bound together
Two examples:
- blood vessels:
Endothelial cells withstand the stress of blood flowing over them constantly
Glycocalyx helps important vascular cells adhere to blood vessels, such as leukocyte and thrombocytes, which are involved in blood clotting
- small intestine:
Made up of microvilli that are covered with glycocalyx
Chyme- liquid from the stomach, which is acidic flows over the microvilli
Therefore cells need extra protection
What is the role of the smooth ER?
Involved in the synthesis of lipids, including cholesterol and phospholipids, which are used in the production of new cellular membrane
Plays an important role in the synthesis of steroid hormones from cholesterol
Contributes to the detoxification of drugs in the liver
What is the role of the Rough ER?
Ribosomes on rough ER specialise in the synthesis of proteins that possess a signal sequence that directs them specifically to the ER for processing
How are lysosomes formed?
The Golgi apparatus forms tiny vesicles that separate from the ends of the Golgi cisternae
Vesicles formed in this way that contain enzymes such as protease and lipase, are primary lysosomes
Secondary lysosomes are formed when primary lysosomes fuse with other membrane- bound vesicles
Define peroxisome and its functions
Small organelle in the cytoplasm
Contains reducing enzyme catalase and some oxidases
Functions:
- breakdown of very long chain fatty acids through beta- oxidation
- detoxify a number of molecules, e.g. Alcohol in the liver and kidney
Describe the structure of cytoskeleton microtubules
Microfilaments, intermediate filaments and microtubules combine to form cytoskeleton
Define actin filament
Made of globu;ar actin subunits
Occur as microfilaments
Important for:
- cell shape
- muscle contraction
- cell adhesion
What is the role of intermediate filaments?
From tough supporting mesh work in cytoplasm
Common in epithelial cells
What is the structure of cilia or flagellum?
Consists of microtubules in a non- fold radial symmetry called axeoneme
Consists of 11 longitudinal fibrils, 2 central and 9 peripheral
The two central microtubules are similar in structure to cytoplasmic microtubules
The 9 peripheral fibrils are doublet microtubules, appearing like a figure of 8 in transverse section
Which cell types are likely to obtain abundant SER, lysosomes, RER, mitochondria and perioxisomes?
Totes, macrophages, exocrine pancreatic cells, cardia muscle cells, kidney tubule cells
Name four enzymes secreted by pancreatic exocrine cell and state the destination of these enzymes
Amylase, protease, pancreatic lipase and elastase
Intestinal duodenum
What cellular function is facilitated by cytoplasmic extensions and lysosomes?
Communication with neighbouring cells, for movement and for specialised processes like wound healing
Lysosomes contain acid hydrolysed, dude with the phagosome to form a phagolysosome where they release their contents which digest the contents of the bacteria
