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

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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

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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
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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

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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

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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)
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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
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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
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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!!!
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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
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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
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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
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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
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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
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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
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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