WEEK 1 Flashcards
What is the difference between a prokaryotic and eukaryotic cell?
Prokaryotes don’t have membrane-bound organelles, Eukaryotes do (eg. nucleus)
Is an animal cell a prokaryotic or eukaryotic cell?
Eukaryotic
What are the organelles of an animal cell?
Nucleus (nuclear envelope, nuclear pore, chromatin and nucleolus), ribosomes, lysosomes, mitochondria, cytoplasm, golgi complex, SER and RER, plasma membrane, microfilaments and microtubules
Describe the nucleus
contains nucleic acids and DNA (made of genes which code for protein synthesis, wrapped around histones to form chromatin), surrounded by nuclear envelope with nuclear pores, surrounded by RER, nucleolus at centre of nucleus-produces mRNA, rest of nucleus made of nucleoplasm
Describe the Rough Endoplasmic Reticulum
has ribosomes on it, involved in protein synthesis
Describe the Smooth Endoplasmic Reticulum
hasn’t got ribosomes on it, involved in lipid and carbohydrate synthesis
Describe the golgi body
modifies and packages proteins into vesicles for transport, digestive enzymes placed into lysosomes (vesicles w/ membranes around them)
Describe mitochondria
site of respiration, releases energy, produces ATP (universal energy carrier molecule). has a double membrane, inner membrane folded into cristae (increases SA for enzymes of respiration) separating mitochondrial matrix from intermembrane space
What is the role of ribosomes?
Site of protein synthesis
What are the functions of lysosomes and peroxisomes?
Digestion and recycling of components that need to be broken down in the cell
What is the cytosol?
the area of cytoplasm not occupied by organelles. water-based solution in which organelles, proteins and other cell structures float
What is the proteoplasm?
everything included within the cell membrane (nucleoplasm and cytoplasm)
What is the cytoplasm?
everything included within the cell membrane excluding the nucleus (cytosol and organelles)
What is endocytosis?
the process of taking material into the cell by means of pockets in the membrane
What are two types of endocytosis?
Phagocytosis and pinocytosis
What is phagocytosis?
type of endocytosis in which large particles are taken in by the cell
What is pinocytosis?
type of endocytosis in which certain cells can engulf and incorporate fluid droplets
What is exocytosis?
the removal of large amounts of materials from the cell
What is the primary protein structure?
sequence of amino acids held by covalent peptide bonds, polypeptide chain w/ projecting side chains that may be: +vely/-vely charged, polar (hydrophilic)/non-polar (hydrophobic)
What is the secondary protein structure?
alpha-helix/beta-pleated sheets held by non-covalent H bonds/electrostatic interactions/van der Waal’s forces
What is the tertiary protein structure?
folding into 3D conformation requiring least energy (+ve/+ve or polar/polar not next to each other), due to H/ionic bonds/disulfide bridges)
What is the quaternary protein structure?
complex of more than one polypeptide chain
How is the overall protein form related to function?
Whether the protein is fibrous/globular
Characteristics and examples of fibrous protein
long and narrow with structural functions, insoluble in water (eg. collagen, keratin, myosin)
Characteristics and examples of globular protein
round/spherical with functional processes, soluble in water (eg. enzymes, haemoglobin, insulin, antibodies)
What are the general functions of proteins?
binding (eg. ligands and receptors)
catalysis (eg. enzymes)
switching (eg. signalling pathways)
structural (eg. cytoskeletal elements)
What are the four processes involved in regulation of protein function?
Synthesis (is it present?-gene expression)
Localisation (is it where it needs to be?)
Modification (is it active?)
Degradation (is it needed anymore?)
What do the functions of many proteins rely on?
Dynamic confirmation that can shift (eg. enzyme activation)
What is protein localisation in the cell?
Proteins directed by sorting signals to the correct site in the cell via transporters located in the membrane
What is constitutive secretion?
Transport of proteins from one compartment to another via transport vesicles
What is regulated secretion?
Secretory vesicles store proteins and receive an extracellular signal to fuse with membrane and release contents
Where and how does most protein modification take place?
Endoplasmic reticulum, includes phosphorylation/glycosylation/methylation
What is the most common method of protein control?
Phosphorylation-phosphate group attached covalently to AA side chains to activate/inhibit proteins
Induces a confirmation change in protein
(Protein kinase catalyst, Protein phosphatase catalyses dephosphorylation)
Describe the process of growth factor signalling
membrane receptor activation leads to dimerisation and phosphorylation, adapter protein binds to phosphorylated receptor in cytoplasm, Ras (G-protein) binds to adaptor, signalling cascade
How can mutations affect protein function?
Insertions/deletions/substitutions/translocations in DNA can change AA sequence, altering secondary and tertiary structure, altering function
Example of mutation causing altered protein function
Cystic Fibrosis-mutated membrane protein (CFTR) due to F508del mutation, causes incorrect folding, causing retention and degradation in ER
What is the unfolded protein response?
Homeostatic response to keep a cell’s folding capacity in balance with its needs, an imbalance in this process leads to ER stress and increased unfolded proteins inhibiting translation and leading to cell death
What is the cell membrane composed of?
Phospholipid bilayer-phosphate head (hydrophilic), glycerol and two fatty acid tails (hydrophobic) x2
What is the fluid mosaic model for membrane structure?
The idea that proteins move within the membrane to come together for functional activity
What is the difference between saturated and unsaturated fatty acids?
Saturated have no carbon carbon doubles bonds in R group whereas unsaturated do
What is the role of cholesterol in membranes?
Intercalated between membrane phospholipids and regulates fluidity by adding rigidity
Structure of cholesterol
Polar head group-rigid planar steroid ring structure-non-polar hydrocarbon tail
What are the benefits of biological membranes being fluid structures?
allows signalling lipids and membrane proteins to rapidly diffuse in lateral plane and interact with one-another
allows membranes to fuse with other membranes
ensures membranes are equally shared between daughter cells following cell division
Give the six membrane protein functions
Transport Enzymatic action Signal transduction Cell-cell recognition Intercellular joining Attachment to cytoskeleton and ECM
Give four types of transmembrane proteins
transporters->Na+ pump
anchors->integrins, link ICM to actin
receptors->bind ligands and cause intracellular signals
signal transduction molecules->pass on and amplify signals
What are the two types of transport across membranes?
Active-requires ATP
Passive-no energy input required
What are the two types of passive transport?
Simple diffusion
Facilitated diffusion
What is simple diffusion?
diffusion of small, uncharged/hydrophobic molecules across the phospholipid bilayer, driven by conc. gradient
What is facilitated diffusion?
diffusion of molecules via membrane proteins, driven by conc. gradient
What are the two classes of facilitated diffusion?
Channel and uniporter carrier proteins
What are channel proteins?
Membrane proteins that form hydrophilic pores in the plasma membrane, most non-directional and fast
What are uniporter carrier proteins?
Membrane protein with a binding site that only specific molecule to be transported can bind to
What are the two forces that compose the net driving force of a charged solute across a membrane?
Electrochemical gradient-concentration (chemical) gradient and voltage across the membrane (electrical force)
What is active transport?
Movement of solutes against concentration gradient, requiring ATP
What is the purpose of the Na+/K+ pump?
maintain electrochemical gradient of Na+ and K+
What is the process of the Na+/K+ pump?
3Na+ bind to pump catalytic subunit, ATP hydrolysis causes phosphorylation of catalytic subunit, conformational change, delivers 3NA+ to exterior and allows 2K+ to bind, dephosphorylation of catalytic subunit, return to original conformation, delivers 2K+ to interior
What are the three ways cells carry out active transport?
Coupled transporters (symport-both solutes in same direction, antiport-solutes move in opposing direction)-Secondary active transport
ATP-driven pumps (requires ATP hydrolysis)-Primary active transport
Light-driven pumps (requires input of light energy)
