Biochemistry Flashcards
(556 cards)
What is a cell?
Basic structural, functional and biological unit of all living organisms
Smallest unit of life replicate indecently
Require nutrients and produce waste
Describe the cell membrane
Selectively permeable biological membrane separating interior and exterior of cell and protecting from surroundings
Involved in cell adhesion, ion conductivity, cell signalling, attachment surface for cell wall, glycocalyx (glycoprotein-polysaccharide surrounding CM of some bacteria and epithelial) and intracellular cytoskeleton
Describe the phospholipid bilayer
Made of hydrophilic heads and hydrophobic tails
Phospholipids spontaneously form self-sealing bilayers
Due to hydrophobic interior charged ions cannot diffuse
Fluid - components move around easily
Mosaic - variety of lipids and proteins
Describe centrosomes
Associated with nuclear membrane in prophase In mitosis, NM breaks down and centrosome nucleated microtubules (cytoskeleton) interact with chromosomes to build mitotic spindle Mother centrosome (oldest) role in making cilia and flagella
Describe lysosomes
Membrane bound organelle that functions as recycling centre by digesting unwanted material in cytoplasm from extracellular and obsolete intracellular components
Contains hydrolytic enzymes capable of digesting almost all biomolecules: proteins, nucleic acids, carbs, lipids, debris
50+ enzymes all active at about pH 5
Describe the cytosol/ICF
Liquid found inside cells separated into compartments by membranes i.e. mitochondrial matrix separates cells into compartments
Eukaryotes - ICF in CM and part of cytoplasm (mitochondria, plastids, organelles minus internal fluids and nucleus
Describe the vacuole
Membrane bound organelle filled with water containing in/organic molecules (enzymes in solution), sometimes engulfed solids
Formed by fusion of multiple vesicles
Shape and function varies depending on needs and type of cell
Role in autophagy, balance between biogenesis and degradation, lysis and recycling of mis-folded proteins
Describe mitochondria
Membrane bound organelles
Main functions are to produce ATP in TCA (respiration) and regulate metabolism
Role in - signalling through mitochondrial reactive O2 specifies
Regulate - MP, apoptosis, Ca signalling (including Ca-apoptosis), cellular metabolism, heme and steroid synthesis
Have oestrogen receptors (mtERs) thus sensitive to hormones
In liver cells, have enzymes that detoxify ammonia (waste product of protein metabolism)
Describe the smooth ER
Site of lipid, phospholipid and steroid synthesis connected to nuclear envelope
Abundant in cells (ovaries, testes, skin oil glands) that secrete these products
Metabolism of carbs and steroids, drug detoxification, attachments of receptors on CMPs
Muscle cell - regulates Ca ion conc.
Describe the cytoskeleton
Dynamic structure made of microfilaments (actin), microtubules (tubulin) and intermediate filaments (only found in animal cells) forming framework for movement of organelles and cell shape
Describe the Golgi body
Modifies, sorts and packages macromolecules for exocytosis or use with in cell primarily those delivered by RER
Transports lipids and involved in creation of lysosomes
N/O-linked goycosylation
Describe the rough ER
Complex responsible for manufacture of lysosomal enzymes (mannose-6-phosphate marker added in cis-Golgi network)
Manufacture of secreted proteins secreted either constitutively (no tag) or regulatory (clathrin and basic AA in signal peptide)
Initial stage of N-linked glycosylation
Describe a vesicle
Variety of functions
Internal environment different from cytosolic as is separate from cytosol thus used for organising cellular substances
Involved in metabolism, transport, buoyancy control, enzyme storage (ready for immediate release), chemical reaction chambers
Describe ribosomes
Site of gene translation
Attaches to mRNA, reads codon. tRNA with complementary anti-codon recruited bringing specific AA building protein.
Continues until reaches stop codon, if none will remain attached forming complex
Describe the nucleus
Cell control centre: maintains integrity of genes and regulates gene expression
Contains DNA and histone proteins to form chromosomes
Has double membrane enclosing entire organelle isolating from cytoplasm, nuclear envelopes and nucleoskeleton (like cytoskeleton)
Describe nucleolus
Organelle found in nucleus that forms around specific chromosomal a previous in nucleus
Made of proteins and RNA
Transcribe and modify rRNA and integrate ribosomal proteins into immature ribosomes
Stress sensor and able to regulate rRNA synthesis based on cell environment
Describe the differences between prokaryotes and eukaryotes
Lack membrane bound nucleus (have nucleoid) and complex organelles
Ribosomal binding site in mRNA is the Shine Delgarno sequence: 8 bases up from AUG
Have mesosomes - folds inwards in PM that increase SA, can be artefact (damage to PM during chemical fixation)
Have cell wall, capsules and flagella (chemotaxis - movement of organism in response to chemical stimuli
Describe gram +ve bacteria (purple)
Thick cell wall of peptidoglycan which is mesh that gives strength
Cell would be spherical and v sensitive to osmotic changes without
Describe gram -ve bacteria (red)
Complex cell wall external to PM with thin peptidoglycan layer
Have outer membrane with lipopolysaccharides conferring
Structural integrity, resistance to chem. attack, toxicity (septic shock, death)
How do many antibiotics work?
Act by inhibiting cell wall synthesis
B-lactam antibiotics (Penicillins) interfere with peptidoglycan synthesis causing cell lysis
What is pH?
Logarithmic measure of conc. of H+ ions (protons) in solution
pH = -log[H+]
What is the physiological pH of the body and why is this important?
pH 7.4
pH affects solubility of substances and the activity of biological systems thus keeping pH constant is important for body
Blood pH<7.3 acidosis
Blood pH>7.5 alkalosis
Define acid, base, conjugated acid and conjugated base
Acid - proton donator, gains -ve charge
Base - proton acceptor, gains +ve charge
Conjugated acid - species formed from addition of H+
Conjugated base - what is left after acid donates proton
What is the major respiratory acid in the body and how is it formed?
CO2
Dissolved in water forming carbonic acid which dissociates releasing H+
CO2 + H2O H2CO3 H+ + HCO3-