2.1.4 The ultra-Structure of eukaryotic cells: membrane bound organelles Flashcards
what cells are eukaryotic? structure
all animal, plant, fungal and protoctist
what type of cell features membrane-bound organelle
eukaryotic ONLY
what is the nucleus surrounded by? structure
a double membrane: the nuclear envelope
what does the nuclear envelope contain? structure
pores
what are two features of the nucleolus? structure
it doesn’t have a membrane around it
it contains RNA
what is cromatin? structure
the generic material, consisting of DNA wound around histone proteins
when is the chromatin spread out or extended? structure
when the cell is not dividing
what happens to chromatin when the cell is about to divide? structure
chromatin condenses and coils tightly into chromosomes (these make up nearly all the organism’s genome
what is the nuclear envelope’s function?
function
the nuclear envelope separates the contents of the nucleus from the rest of the cell
what do the outer and inner nuclear membranes do in some regions? function
the outer and inner nuclear membranes fuse together in some regions
what happens to the outer and inner nuclear membranes, in some regions to allow for diffusion etc? function
they fuse together in some places so dissolved substances and ribsomes can pass through
what do the nuclear pores enable to happen? function
larger substances (eg MRNA) to leave the nucleus, and substances (eg steroid hormones) may enter the nucleus, from the cytoplasm
where are ribosomes made?
nucleolus
summary of nucleus: 4 points. function
-control centre of the cell
-stores the organism’s genome
-transmits genetic information
-provides the instructions for protein synthesis
what is the RER? Rough Endoplasmic Reticulum. structure
RER is a system of membranes containing fluid-filled cavities (cisternae) that are continuous with the nuclear membrane
what is the RER coated in? structure
ribosomes
what are cisternae? structure
fluid filled cavities, in rER, sER, GA
what is the RER? function
intracellular transport system
what do the cisternae form in the RER? function
channels that transport substances from one area of a cell to another
what does the rER provide for ribosomes?
large surface area
what are the ribosomes function? function
assemble amino acids into proteins- protein synthesis
describe the route of proteins inside/out of RER. funtion
- ribosomes assemble amino acids into proteins
-these proteins then actively pass through the membrane into the cisternae
-they are transported to the Golgi apparatus (for modification and packaging)
what is the SER? Smooth Endoplasmic Reticulum. structure
SER is a system of membranes, containing cisternae (fluid-filled cavities) that are continuous with the nuclear membrane
how are the sER and rER different structurally? structure
rER has ribosomes whereas the sER do not
what does the SER contain? function
enzymes that catalyse reactions involved in lipid metabolism
what do the enzymes the sER contains, that catalyse reaction involved with lipid metabolism, do? function
-synthesis of cholesterol
-synthesis of lipids/phospholipids needed by the cell
-synthesis of steroid hormones
what is the SER involved with? function
absorption, synthesis and transport of lipids (from the gut) and production, processing and storage of lipids, carbohydrates and steroids
what does the Golgi apparatus consist of? structure
stack of membrane bound flattened sacs and cisternae
what brings materials to/from the Golgi apparatus?
secretory vesicles bring materials to/from the Golgi apparatus
how are proteins modified in the Golgi apparatus? function
-adding sugar molecules
-adding lipid molecules
-being folded into 3D shape
what does adding sugar molecules to proteins make in Golgi apparatus? function
sugar molecules + protein ——> glycoproteins
what does adding lipid molecules to proteins make in the Golgi apparatus?
lipid molecules + protein ——> lipoproteins
what happens to the proteins once they have been modified in the Golgi apparatus? function
the proteins are packaged into vesicles that are pinched off, then they:
-stored in a cell
-or moved to the plasma membrane
why are proteins moved to the plasma membrane? function
-to be incorporated into the plasma membrane
-or exported outside the cell
mitochondria/mitochondrion difference
-rion ——> singular
-ria ——> plural
what shape can mitochondria be? structure
spherical, rod shaped or branched
how long are mitochondria? structure
2-5 µm long
what are mitochondria surrounded by? structure
two membranes with a fluid filled space between them
what is the inner membrane of mitochondria highly folded into? structue
the inner membrane is highly folded into cristae
what is the inner part of the mitochondrion? structure
the inner part is a fluid filled matrix
what is the function of a mitochodrion? function
it is the site of ATP (energy currency) production, during aerobic respiration
where are mitochondria made? function
they are self replicating (more can be made if the cell’s energy needs increase)
where are mitochondria abundant? function
in cells where much metabolic activity takes places
-liver cells
-at synapses between neurones (where neurotransmitter is synthesised and released)
how big are chloroplasts? structure
large
4-10 µm long
where are chloroplasts found? structure
ONLY in plant cells and some protoctists
what are chloroplasts surrounded by? structure
a double membrane or envelope
what are thylakoids? structure
flattened membrane bound sacs
resemble plates in chloroplast
what is the inner membrane of the chloroplast continuous with? structure
the inner membrane of the chloroplast continuous with thylakoids
what do thylakoids contain? structure
chlorophyll
what is each stack of thylakoids called? structure
each stack of thylakoids called a granum
what is the plural of a granum?
grana
what is the fluid filled matrix in chloroplasts? structure
the stroma
what do substances do chloroplasts contain? structure
loops of DNA and starch grains
what is chloroplasts the site of? function
site of photosynthesis
what happens at the first stage of photosynthesis? the light dependent stage function
-it occurs in the grana, the light energy is trapped by chlorophyll and used to make ATP
-water is also spilt to supply hydrogen ions
what happens at the second stage of photosynthesis? the light independent stage (Calvin Cycle) function
- hydrogen reduces carbon dioxide, using energy from ATP, to make carbohydrates, which occurs in the stroma
where are choloplasts abundant?
leaf cells
— palisade mesophyll layer
what is the vacuole surrounded by? structure
the tonoplast which contains fluid
what is the tonoplast? structure
a membrane surrounding the vacuole which contains fluids
where can a large permanent vacuole be found? function
ONLY plant cells have a large permanent vacuole
what is the vacuole filled with? function
water and solutes
what is the function of the vacuole? function
maintains cell stability
what happens when the vacuole is full? structure
it pushes against the cell wall, making the cell turgid
why is it ideal for all the plant cells to be turgid? function
this helps to support the plant
what are lysosomes formed from? structure
Golgi apparatus
what is a lysosome? structure
a small bag, formed from the GA, each is surrounded by a single membrane
what do lysosomes contain? structure
powerful hydrolytic (digestive) enzymes
what cells are abundant in lysosomes? structure
phagocycotic cells that can ingest and digest invading pathogens
what does hydrolytic mean? structure
digestive
what is the 2 roles of the lysosomes? function
-they keep the powerful hydrolytic enzymes separate from the rest of the cell
-they can engulf old cell organelles and foreign matter, and return the digested components to the cell for reuse
what are cilia and undulipodia? structure
protrusions from the cell and are surrounded by the plasma membrane
what are cilia and undulipodia formed from? structure
centrioles
what does each cilia and undulipodia contain?
microtubules
where is cilia abundant? function
the epithelial cells lining the airways each have many hundreds of cilia that beat and move the band of mucus
what does the cillia that nearly all cell types in the body have, do? function
acts as an antenna
-it contains receptors and allows the cell to detect signals about its immediate environment
what is the only type of human cell to have an undulipodium? function
a spermatozoon
what is the difference between a cilia and an undulipodium? structure
the undulipodium is a longer cilia
what does the undulipodium enable? function
the undulipodium enables the spermatozoon to move
what is the difference between eukaryotic and prokaryotic ribosomes?
eukaryotic has 80s
prokaryotic has 70s
what are the two chambers of a chloroplast?
thylakoid and stroma
what are all cells surrounded by?
a plasma membrane which controls the exchange of materials between the internal cell environment and the external environment (partially permeable)
what is the plasma membrane formed from?
from a phospholipid bilayer
what is the diameter of a plasma membrane?
0.01µm
what connects the cytoplasm to neighbouring plant cells?
narrow threads of cytoplasm (surrounded by a cell membrane) called plasmodesmata connect the cytoplasm of neighbouring plant cells
what are chromosomes?
chromosomes are made of sections of linear DNA tightly wound around histone proteins
what is chromatin?
the material from which chromosomes are made- found in the nucleus
what enzymes does the fluid filled matrix contain?
The matrix formed by the cristae contains respiratory enzymes needed for aerobic respiration, producing ATP
what other organelle are found in the matrix?
Small circular pieces of DNA (mitochondrial DNA) and ribosomes are also found in the matrix (needed for replication)
what are grant joined together by in chloroplasts?
grana are joined together by lamellae (thin and flat thylakoid membranes)
what are lamellae?
thin and flat thylakoid membranes, that join grana together
what is a ribosome made up of?
each ribosome is a complex of ribosomal RNA (rRNA) and proteins
what are 70s ribosomes composed of?
composed of 50S and 30S subunits
what are 80s ribosomes composed of?
composed of 60S and 40S subunits
where are 70s ribosomes also found?
mitochondria and chloroplasts
what is a vesicle?
a membrane-bound sac for transport and storage
what are lysosomes used by most often?
used extensively by cells of the immune system and in apoptosis (programmed cell death)
what is apoptosis?
programmed cell death
what is a centriole structure?
hollow fibres made of microtubules
what is a centrosome? structure
two centrioles at right angles to each other form a centrosome
what is a centrosome? function
organises the spindle fibres during cell division
where a centrioles not found?
not found in flowering plants and fungi
