Eukaryotic Cell Structure Flashcards
1
Q
what are eukaryotic cells
A
eukaryotic cells have a more complex ultrastructure than prokaryotic cells
their cytoplasm is divided into membrane-bound compartments called organelles - bound by a single or double membrane
2
Q
why is the compartmentalisation of eukaryotic cells advantageous
A
it allows
- enzymes and substrates to be localised and therefore available at higher concentrations
- damaging substances are separated (e.g: digestive enzymes)
- optimal conditions to be maintained for certain processes (e.g: pH for digestion)
- numbers and location of organelles can be altered depending on requirements of the cell
3
Q
what structures do animal and plant eukaryotic cells share
A
- membrane bound organelles including a nucleus, RERs, SERs, golgi apparatus, vesicles, lysosomes, mitochondria, plasma membrane
- 80S ribosomes
- cytoskeletons, cytoplasm
4
Q
what are some key differences between animal and plant cells
A
animal cells contain
- centrioles
- microvilli
plant cells contain
- cellulose cell walls
- large permanent vacuoles
- chloroplasts
5
Q
what can eukaryotic cells do in complex multicellular organisms
A
become specialised for specific functions and have specific adaptations (cells can look very different in shape and in terms of what organelles it contains)
- e.g: rbs are biconcave and don’t have a nucleus
6
Q
plasma membrane function
A
- lipid bilayer of phospholipids that functions as a barrier between aqueous solutions
- thin line surrounding the cell
- tends to show darker on micrographs (proteins)
- controls the exchange of materials between the internal cell environment and the external environment (partially permeable)
7
Q
nucleus function
A
- where DNA is replicated and transcribed
- contains DNA as well as enzymes needed to make DNA
- contains chromatin (make chromosomes, which are made of linear DNA wound around histones)
- usually surrounded by endoplasmic reticulum
- stains dark but may have internally lighter areas (difference in density), darker regions are nucleoli - ribosome production
- double membrane with many pores (transport) - nuclear envelope
- pores allow for mRNA and ribosomes to travel out of the nucleus as well as enzymes and signalling molecules to travel in
- sphere-ish
- pores may be visible
8
Q
rough endoplasmic reticulum function
A
- central role in the synthesis and transport of polypeptides
- bound 80S ribosomes which synthesise the polypeptide and release it to the inside of the RER
- series of connected, flattened membranous sacs, formed from folds of membrane continuous with nuclear envelope
- usually found near the nucleus (amount depends on cell type)
- ribosomes on RER process material from the nucleus to make proteins
- proteins move from ribosomes to cisternae, then bud off to vesicles that carry then to golgi apparatus before being secreted out of the cell
9
Q
smooth endoplasmic reticulum function
A
- central role in the synthesis of phospholipids and cholesterol
- for the formation and repair of membranes
- series of connected, flattened, membranous sacs
- usually found further from the nucleus that RER
- visible as pockets
- don’t synthesise proteins!!!
10
Q
free ribosomes function
A
- synthesise polypeptides during translation to become proteins that function WITHIN the cell
- often the smallest structure in an electron micrograph
- found freely in cytoplasm of all cells
- complex of ribosomal RNA and proteins, constructed in the nucleolus
- made of 2 subunits (60S and 40S)
- site of translation
11
Q
mitochondria function
A
- adapted for the production of ATP by aerobic cellular respiration
- evolved from prokaryotic cells
- bound by a double membrane
- circular or oval
- stain dark
- have infoldings of inner membrane called cristae
- matrix is formed by cristae - contains enzymes needed for aerobic respiration, like a cytoplasm
- small bits of DNA and ribosomes found in the matrix
12
Q
golgi apparatus function
A
- modifies polypeptides (proteins and lipids) into their functional state
- sorts, concentrates and packs proteins into vesicles to be transported
- flattened stacks with a clear inside, made of cisternae
- proteins that go through the golgi apparatus are usually exported (e.g. hormones such as insulin), put into lysosomes (such as hydrolytic enzymes) or delivered to membrane-bound organelles
- have vesicles on their ends
13
Q
vesicles function
A
- contain/store and transport materials within cells
- membrane bound
- circular
- stain dark (proteins stored)
- may be clumped to one side in secretory cells
- membrane fuses with plasma membrane for out and in transport
14
Q
lysosome function
A
- specialist form of vesicles which contain hydrolytic enzymes (break down bio molecules)
- degrade and eject or recycle waste materials such as worn out organelles or pathogens that have been engulfed by phagocytes
- used by cells of the immune system and in apoptosis (programmed cell death)
- small spherical organelles
15
Q
chloroplasts function
A
- adapted for photosynthesis (light energy and water and carbon dioxide –> glucose)
- bound by a double membrane
- in plant cells
- membrane-bound compartments called thylakoids containing chlorophyll stack to form structures called grana
- grana are joined together by lamellae (thin and flat thylakoid membranes)
- site of photosynthesis: light-dependent stage takes place in the thylakoids, light-independent stage (calvin cycle) takes place in the stroma
- also contain small circular pieces of DNA and ribosomes used to synthesise proteins needed in chloroplast replication and photosynthesis
16
Q
large permanent vacuoles function
A
- stores water and/or metabolic waste
- plant cells: maintains turgor pressure
- bound by a single membrane: tonoplast
- clear (fluid inside)
- fill most of plant cell
- have cell sap
17
Q
cell wall function
A
- extra-cellular component (not an organelle)
- fungi and plant cells
- helps develop turgor pressure
- protects the cell
- external to plasma membrane, offers structural support
- thicker line, light grey colour
- structural support given by cellulose (plants) and peptidoglycan in bacterial cells
- narrow threads of cytoplasm (surrounded by a cell membrane) called plasmodesmata connect the cytoplasm of neighbouring plant cells
18
Q
flagellum function
A
- found in specialised cells
- similar in structure to cilia, made of longer microtubules
- long protrusion of cell membrane
- usually only 1-2 present
- microtubules in a 9+2 pattern
- contract to provide cell movement through a solution (e.g: sperm cells)
19
Q
centrioles function
A
- hollow fibres made of microtubules (filaments and proteins) that can expand and contact
- two centrioles at right angles to each other form a centrosome which organises the mitotic spindle fibres during cell division
- serve as anchor points for microtubules in the cytoplasm and for cilia and flagella (when modified to become a basal body)
- paired, cylindrical
- 9 groups of 3 microtubules organised with radial symmetry
- not found in flowering plants and fungi
20
Q
microtubules/cytoskeleton function
A
- makes up the cytoskeleton of the the cell, about 25 nm in diameter
- made of α and β tubulin combined to form dimers, the dimers are then joined into protofilaments
- thirteen protofilaments in a cylinder make a microtubule
- the cytoskeleton is used to provide support and movement/division abilities to the cell, it helps to organise cell parts
- long fibrous strands
- stained using fluorescence
21
Q
microvilli function
A
- cell membrane projections
- used to increase the surface area of the cell surface membrane → +SA → + rate of exchange of substances
- shorter and more tightly packed than cilia
- do not have a 9+2 arrangement of microtubules
22
Q
cilia function
A
- hair-like projections made from microtubules
- allows movement of substances over cell surface
- move regularly back and forth, can move cell or things across the cell surface
- microtubules arranged in a 9+2 pattern
- dark centre - microtubules
23
Q
draw a plant and an animal eukaryotic cell
A
see photo flash cards
