Key Points Document Flashcards
Cell wall function
Provides rigid shape
Stops osmotic lysis
Outline the roles of organelles in the production, transport and release of proteins from eukaryotic cells
DNA in nucleus codes for the protein
Ribosomes on the RER produce the protein
Mitochondria produce ATP needed for protein synthesis
Golgi apparatus modifies and packages protein into
vesicles
Vesicles transport the protein to the cell surface membrane where they fuse with it and undergo exocytosis to desired location
Compare and contrast DNA in prokaryotes and eukaryotes
Nucleotide structure identical
Nucleotides joined by phosphodiester bonds
Deoxyribose sugar
DNA in chloroplast and mitochondria similar to prokaryote
Eukaryotic longer
Eukaryotic contains introns
Eukaryotic is linear, Prokaryotic circular
Eukaryotic membrane bound, Prokaryotic free floating
Eukaryotic associated with histone
Differences between plant and prokaryotic DNA
Plant associated with histones, Prokaryotic not Plant linear, Prokaryotic circular Plants have no plasmids, Prokaryotes do Plants have introns, Prokaryotes do not Plants longer
How is cholera different to epithelial cells
Cholera is prokaryotic, epithelial Eukaryotic
Cholera has no nuclear membrane and DNA free floating and circular
Cholera has no membrane bound organelles
Or SER/RER
Cholera only has small ribosomes
Cholera has a flagella, capsule, plasmid or cell wall
Advantage of TEM over SEM
Higher resolution
Higher magnification so more detail/internal details to be seen
Cross sections can be taken
Advantage of SEM over TEM
Can be 3D
Thin sections do not need to be prepared
Shows surface of specimen
Advantages vs disadvantages of TEM
Small objects can be seen
High resolution
Electrons wavelength is shorter than light
Cant look at living cells, must be dead
Must be a thin specimen
Must be in a vacuum
Risk of creating artefacts in preparation
Why isotonic
Prevents osmosis so organelle doesn’t burst of shrivel
Why ice cold
Reduce enzyme activity so organelles are not digested
Why add a buffer
Maintain a constant pH so proteins do not denature
How can cell fractionation and centrifugation be used to isolate mitochondria from a suspension of animal cells
Cell homogenisation to break open cells and release organelles
Filter to remove large debris like cell walls
Use isotonic solution to prevent osmotic damage to mitochondria
Keep ice cold to prevent damage to organelles by enzymes
Use a buffer to maintain pH so proteins don’t denature
Use differential centrifugation to separate nucleus in first pellet since densest
Re spin supernatant at a higher speed and the next pellet is mitochondria
Observe with microscope to check it is mitochondria
Why fluid mosaic
Fluid because molecules can move around within the membrane
Mosaic because made up of a variety of different molecules unevenly distributed
How is movement across cell membrane affected by membrane structure
Phospholipid bilayer allows lipid soluble substances to enter by simple diffusion
Stops polar, charged and water soluble molecules entering
Carrier proteins allow active transport
Channel and carrier proteins allow facilitated diffusion
Cholesterol affects permeability
Surface area determines how much diffusion
Number and type of channel proteins and carrier proteins determines how much is transported and what is transported
Non-specific defence mechanisms against pathogen
Phagocytosis Pathogen engulfed by phagocyte Entering its cytoplasm in a vesicle Lysosomes fuse Releasing hydrolytic digestive enzymes Lysozymes break down the pathogen Waste ejected from cell via exocytosis Becomes and APC
Cells that can stimulate an immune response
Abnormal body cells
Pathogens
Cells from other organisms like transplant
Cells infected by virus
How do vaccines cause production of antibodies
Vaccine contains antigens from pathogen
Macrophage presents the antigens on its cell
T helper cell with complementary receptor protein binds to antigen
Stimulating specific B cell with complementary antibody on its surface
B cell divides by mitosis in clonal selection
Producing more of the antibody
And memory B cells
B cells secrete large amounts of antibody
How does the humoral response lead to immunity
B cells specific to antigen undergo clonal selection by mitosis
B cells produce plasma cells and memory cells
Second infection produces antibodies quickly in large volumes
Role of antibodies in stimulating phagocytosis
Bind to antigen and act as markers for opsonisation
Clump pathogens together so easier to destroy
Active vs passive immunity
Active involves memory cells
Active involves production of antibody by plasma cells
Passive involves antibody introduced from external source
Active is long term because antibody produced in response to antigen
Passive is short term since antibody is broken down
Active can take longer to develop and passive is faster acting
Monoclonal antibody
Antibodies produced from a single clone of B cells
Why are monoclonal antibodies specific
Specific primary structure
Specific tertiary structure
So can only bind to one type of antigen
Structure of HIV
Human Immunodeficiency Virus
RNA is the genetic material
Reverse transcriptase contains genetic blueprint to rewrite human gene to manufacture viral particles
Protein capsid
Phospholipid envelope made from cell membrane of cell budded off
Attachment proteins allow it to bind to host cell
