Unit 2 - Cells Flashcards
what is the structure of an animal cell?
see labelled diagram
what is the structure of a plant cell?
see labelled diagram
what is the structure of an algal cell?
similar to plant cells - same organelles including a cell wall & chloroplasts
what is the structure of a fungal cell?
similar to plant cells
cell wall of chitin
do not have chloroplasts as they do not photosynthesise
what is the function of the cell surface (plasma) membrane?
regulates the movement of substances into & out of the cell
separates cell contents from surroundings
allows different conditions to be maintained within the cell
allows cell interaction/attachment to form tissues
has receptor molecules, which allow it to respond to chemicals like hormones
selectively permeable
what is the structure of the cell surface (plasma) membrane?
made of phospholipid bilayer, embedded proteins &
lipids
intrinsic - span the bilayer, extrinsic - partially embedded
hydrophilic phosphate heads on the outside, hydrophobic lipid tails on the inside
on the surface of animal cells & on the inside of cell walls
what is the function of the nucleus?
to control the cell’s activities by coding for polypeptides
contains DNA as chromatin (DNA wound around histone proteins)
the nucleolus is the site of ribosomal RNA & synthesis of ribosomes
nuclear envelope & nuclear pores separate DNA from cytoplasm
nuclear pores control the movement of molecules between nucleus & cytoplasm
what is the structure of the nucleus?
the nuclear envelope is a double membrane that has nuclear pores
histone protein-bound linear DNA is arranged as chromosomes
1 or more nucleoli
what is transcription?
copying a section of DNA into RNA
what is translation?
synthesis of amino acids & so a polypeptide from an RNA template
what is the function of ribosomes?
the site of protein synthesis & translation
what is the structure of ribosomes?
very small
made from protein, RNA & rRNA subunits (rRNA is made in nucleolus)
made up of a large subunits & a small subunit
located in the cytoplasm and attached to RER
70s ribosomes are in prokaryotes & chloroplasts & mitochondria
80s ribosomes are in eukaryotes
what is the function of the rough endoplasmic reticulum (RER)?
site of protein synthesis
what is the structure of the RER?
a system of membrane-bound flattened sacs & fluid-filled cisternae (spaces)
the surface is covered with 80s ribosomes
what is the function of the smooth endoplasmic reticulum (SER)?
site of lipid/steroid hormone synthesis
processes lipids
fat storage & transport
triglycerides - storage of Ca2+ in muscle fibres
phospholipids - make new membrane
what is the structure of the smooth endoplasmic reticulum (SER)?
a system of random membrane-bound flattened sacs & fluid-filled cisternae (spaces)
the surface is not covered in ribosomes
what is the function of the golgi apparatus?
to covalently modify proteins (that have come from the RER)
processes & sorts proteins according to their destination
releases golgi vesicles (e.g. secretory for exocytosis or lysosomes)
how are proteins modified in the golgi apparatus?
add carbohydrates to protein to form glycoprotein
add lipids to protein to form lipoprotein
what is the structure of the golgi apparatus?
stacks of 4-8 membrane-bound flattened sacs with fluid-filled cisternae
vesicles from RER or SER arrive at golgi & fuse with it
contains enzymes that modify proteins
produces golgi vesicles at the edges of the sacs
what is the function & structure of golgi vesicles?
to store lipids & proteins made by the golgi apparatus & transports them out of the cell via the cell surface membrane
a small fluid-filled sac in the cytoplasm, surrounded by a membrane
produced by golgi apparatus
what is the function of lysosomes?
contains hydrolytic enzymes (lysozyme)
to fuse with vesicles/phagosomes containing bacteria during phagocytosis
to digest invading cells
to break down unwanted organelles & cellular debris/worn out components
what is the structure of lysosomes?
round organelle surrounded by a membrane with no clear internal structure
contain hydrolytic enzymes (lysozyme)
produced by & pinch off from golgi
describe the endomembrane transport system
- autoradiography can track the amino acids through the cell from time 0
- through the RER after 10 mins
- through the golgi after 30-60 mins
- being secreted after approximately 90 mins
what is the function of mitochondria?
site of aerobic respiration (energy transfer from organic molecules to ATP & energy release)
link reaction
has a role in Kreb’s cycle
oxidative phosphorylation (releasing energy to make ATP)
what is the structure of mitochondria?
oval-shaped
double membrane (outer & inner mitochondrial membrane)
outer membrane regulates entry & exit of substances
intermembrane space
inner membrane is folded into cristae & matrix that contains enzymes for link reaction & Kreb’s cycle (large sa to hold the electron transfer chain & the enzyme ATPsynthase)
large sa maintained by sausage-shape & short diffusion distance so quick diffusion in & out
70s ribosomes
DNA loops
what is the function of chloroplasts?
site of photosynthesis
light dependent reaction on thylakoid membrane
light independent reaction in stroma
what is the structure of chloroplasts?
small, flattened
smooth double membrane (chloroplast envelope)
stroma (fluid-filled) where the synthesis of sugars happens - light independent reaction (calvin cycle)
thylakoid: where light dependent reaction happens - (fluid-filled membrane sacs) in stacks called grana that contain chlorophyll (photosynthetic pigment) + intergranal/stromal lamellae that link grana
contains 70s ribosomes & loops of chloroplast DNA
contains ATPsynthase (makes ATP)
what is the function of the cell wall?
to provide mechanical strength to prevent cell lysis (bursting) due to osmotic entry of water
to allow plants to develop turgor pressure/become turgid
to allow water to pass along it (from cell wall to cell wall by apoplast pathway) so helps water move through plant
freely permeable
what is the structure of the cell wall in plant cells?
made of cellulose molecules - polymers of b-glucose
cellulose is bundled into microfibrils with multiple h-bonds
microfribrils form mesh lattice which is freely permeable
thin middle lamella that marks the boundary b/w2 cells & join adjacent cells together with Ca pectate
plasmodesmata channels for exchanging substances with adjacent cells
in fungi, the cell wall is made of chitin
what is the function of the vacuole?
to change volume to maintain turgidity, giving support
to store substances e.g. minerals, pigments, sugars
contains enzymes for breaking down molecules
isolates unwanted chemicals inside the cell
what is the structure of the vacuole?
large, fluid-filled (water) & membrane-bound (tonoplast)
the tonoplast is selectively permeable
contains hydrolytic enzymes to break down molecules
all mature plant cells have a vacuole
contains cell sap
in cytoplasm
what is a tissue?
a group of similar, specialised cells that work together to perform a particular function
what is an organ?
a group of tissues that work together to perform a particular function
what is an organ system?
a group of organs that work together to perform a particular function
make up an organism
what is the structure & function of the flagella?
hair-like structure
rotates to allow the cell to move
what is the structure & function of the nucleoid?
not attached to histone proteins
code for polypeptides & genetic information for replication
what is the structure & function of the cytoplasm?
contains simple, non-membrane-bound organelles
aqueous stage where reactions occur
what is the structure & function of the ribosomes in prokaryotes?
70s
site of protein synthesis
what is the structure & function of the slime capsule?
protect bacterium from other cells e.g. from immune system
allow bacteria cells to stick to each other for protection
surrounds cell wall
what is the structure & function of the cell wall in bacteria?
made of murein/peptidoglycan (glycoprotein)
freely permeable
supports cell & prevents osmotic lysis
what is the structure & function of the cell surface membrane in bacteria?
phospholipid bilayer
selectively permeable
controls movement of substances into & out of the cell
what is the structure & function of the plasmids?
small rings of DNA in the cytoplasm
contain several genes e.g. antibiotic resistance that can be transferred to other bacteria cells via pili
eukaryotic cells vs prokaryotic cells
distinct nucleus w nuclear envelope vs no true nucleus (DNA as nucleoid in cytoplasm)
DNA associated with histone proteins, forming chromatin vs DNA not associated with histone proteins
there are no plasmids & DNA is linear vs some DNA might be in circular strands called plasmids
contain complex, membrane-bound organelles (RER, SER, mitochondria, GA) vs no membrane-bound organelles
chloroplasts might be present vs no chloroplasts, sometimes bacterial chlorophyll associated with CSM
10-100 micrometres vs 1-10 micrometres
80s & 70s ribosomes vs 70s ribosomes only
cell wall of cellulose vs cell wall of murein/glycoprotein
no outer capsule vs may have slime capsule
what are viruses?
acellular/non-living particles
they have no metabolism & cannot replicate outside of a host cell
what is the structure of a virus?
nucleic acids e.g. DNA & RNA (single-stranded) as genetic material but can only reproduce inside living host cells
nucleic acid is enclose in a protein coat (capsid), which protects nucleic acid from being digested by host enzymes
attachment proteins attach to host cell’s receptor protein e.g. gp120 on HIV
some viruses (e.g. HIV) have PL bilayer membrane
HIV has enzyme called reverse transcriptase