2.1 (cell structure) Flashcards
structure of the cell surface membrane diagram
all cells are surrounded by a cell surface membrane which controls the
exchange of materials between the internal cell environment and the external environment
the membrane is described as being
partially permeable
the cell membrane is formed from a
- phospholipid bilayer of phospholipids
- spanning a diameter of around 10 nm
cell wall diagram
cell walls are formed outside of the cell membrane and offer
structural support to cell
structural support is provided by the what in plants
polysaccharide cellulose
structural support is provided by the what in most bacterial cells
peptidoglycan
narrow threads of cytoplasm (surrounded by a cell/plasma membrane) called what connect the cytoplasm of neighbouring plant cells
plasmodesmata
nucleus diagram
the nucleus of a cell contains chromatin (a complex of DNA and histone proteins) which is the
genetic material of the cell
the nucleus is separated from the cytoplasm by a double membrane which is also called the
nuclear envelope
the nucleus is separated from the cytoplasm by a double membrane (the nuclear envelope) which has
many pores
nuclear pores are important channels for allowing
- mRNA and ribosomes to travel out of the nucleus
- as well as allowing enzymes (eg. DNA polymerases) and signalling molecules to travel in
nuclear pores are important channels for allowing what to travel out of the nucleus
- mRNA
- and ribosomes
nuclear pores are important channels for allowing to travel in
- enzymes (eg. DNA polymerases)
- and signalling molecules
the nucleus contains
chromatin (the material from which chromosomes are made)
the nucleus contains chromatin which is the material from which
chromosomes are made
chromosomes are made of sections of
- linear DNA
- tightly wound around proteins called histones
chromosomes are made of sections of linear DNA tightly wound around proteins called
histones
the nucleolus is the site of
ribosome production
darkly stained regions can be observed which are individually termed
- nucleolus
- plural: nucleoli
mitochondria diagram
a mitochondrion inner membrane has protein complexes vital for the later stages of
aerobic respiration embedded within it
mitochondria are the site of
aerobic respiration within eukaryotic cells
mitochondria are surrounded by a double-membrane with the inner membrane folded to form
cristae
the matrix formed by the cristae contains
enzymes
the matrix formed by the cristae contains enzymes needed for
- aerobic respiration
- producing ATP
small circular pieces of DNA (mitochondrial DNA) and ribosomes are also found in the
matrix
small circular pieces of DNA (mitochondrial DNA) and ribosomes are also found in the matrix, needed for
replication
chloroplast diagram
as well as mitochondria, chloroplasts are also surrounded by a
double-membrane
membrane-bound compartments called thylakoids containing chlorophyll stack to form structures called
grana
membrane-bound compartments called what, containing chlorophyll stack to form structures called grana
thylakoids
grana are joined together by
- lamellae
- thin and flat thylakoid membranes
chloroplasts are the site of
photosynthesis
the light-dependent stage takes place in the
thylakoids
the light-independent stage (Calvin Cycle) takes place in the
stroma
chloroplasts also contain small circular pieces of DNA and ribosomes used to synthesise proteins needed in chloroplast replication and
photosynthesis
ribosome diagram
ribosomes are formed in the nucleolus and are composed of almost equal amounts of
RNA and protein
ribosomes are found freely in the cytoplasm of all cells or as part of the
rough endoplasmic reticulum in eukaryotic cells
each ribosome is a complex of
- ribosomal RNA (rRNA)
- and proteins
80S ribosomes (composed of 60S and 40S subunits) are found in
eukaryotic cells
70S ribosomes (composed of 50S and 30S subunits) are found in
prokaryotes, mitochondria and chloroplasts
ribosomes are the site of
translation (protein synthesis)
endoplasmic reticulum diagram
Rough Endoplasmic Reticulum (RER) surface covered in
ribosomes
Rough Endoplasmic Reticulum (RER) formed from continuous folds of
- membrane
- continuous with the nuclear envelope
Rough Endoplasmic Reticulum (RER)
processes
proteins made by the ribosomes
Smooth Endoplasmic Reticulum (ER) involved in the production, processing and storage of
lipids, carbohydrates and steroids
Golgi apparatus (golgi complex) diagram
golgi apparatus is flattened sacs of
- membrane
- similar to the smooth endoplasmic reticulum
golgi apparatus modifies
proteins and lipids
golgi apparatus modifies proteins and lipids before packaging them into
golgi vesicles
the vesicles then transport the
- proteins and lipids
- to their required destination
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
large permanent vacuole diagram
large permanent vacuole is a sac in plant cells surrounded by the
- tonoplast
- is a selectively permeable membrane
vacuoles in animal cells are not
permanent, and small
vesicle diagram
a vesicle is a
membrane-bound sac for transport and storage
lysosome diagram
a lysosome is a specialist form of vesicles which contains
- hydrolytic enzymes
- (enzymes that break biological molecules down)
lysosomes break down waste materials such as worn-out organelles, used extensively by cells of the
immune system
lysosomes break down waste materials such as worn-out organelles, used extensively by cells of the immune system and in
apoptosis (programmed cell death)
centriole diagram
centrioles are hollow fibres made of
microtubules
centrioles are hollow fibres made of microtubules, two centrioles at right angles to each other form a
centrosome
hollow fibres made of microtubules, two centrioles at right angles to each other form a centrosome, which
organises the spindle fibres during cell division
centrioles are not found in
flowering plants and fungi
microtubules diagram
microtubule makes up the cytoskeleton of the cell about
25 nm in diameter
microtubule made of α and β tubulin combined to form
dimers
microtubule made of α and β tubulin combined to form dimers, the dimers are then joined into
protofilaments
how many protofilaments in a cylinder make a microtubule
13
microtubule makes up the cytoskeleton of the cell which is used to provide
support and movement of the cell
microvilli diagram
microvilli are cell membrane projections that
increase the surface area for absorption
cilia diagram
cilia are hair-like projections made from
microtubules
cilia allows
the movement of substances over the cell surface
flagella diagram
flagella has similar in structure to cilia, made of longer
microtubules
flagella contract to provide cell movement for example in
sperm cells
in complex multicellular organisms, eukaryotic cells become
specialised for specific functions
these specialised eukaryotic cells have
specific adaptations to help them carry out their functions
for example, the structure of a cell is adapted to help it carry out its
function
structural adaptations include
- the shape of the cell
- the organelles the cell contains
structural adaptions examples include
- red blood cells are biconcave and do not contain a nucleus, this makes more space inside the cell so that they can transport as much oxygen as possible
- cells that make large amounts of proteins will be adapted for this function by containing many ribosomes (the organelle responsible for protein production)
cells that make large amounts of proteins will be adapted for this function by containing
many ribosomes (the organelle responsible for protein production)
neurones (nerve cells) diagram
nerve cells (neurones) have a characteristically elongated structure which allows them to
coordinate information from the brain and spinal cord with the rest of the body
neurone function
conduction of impulses
an adaption of a neurone is that it has a cell body where
- most of the cellular structures are located
- and most protein synthesis occurs
an adaption of a neurone is that it has extensions of the cytoplasm from the cell body which form
- dendrites (which receive signals)
- and axons (which transmit signals)
extensions of the cytoplasm from the cell body form dendrites (which receive signals) and axons (which transmit signals), allowing the neurone to
communicate with other nerve cells, muscles and glands
an adaption of a neurone is that the axon (the main extension of cytoplasm away from the cell body) is covered with a
- fatty sheath
- which speeds up nerve impulses
- axons can be up to 1m long in some animals and can therefore enable fast communication over long distances
skeletal muscle cell diagram
muscle cells contain layers of fibres that allow them to
contract
an adpation of muscle cells is that there are three different types of muscle in animals
skeletal, smooth and cardiac (heart)
an adpation of muscle cells is that all muscle cells have layers of
- protein filaments (fibres) in them
- these layers can slide over each other
- causing muscle contraction
an adpation of muscle cells is that they have a high density of
- mitochondria
- to provide sufficient energy (via respiration) for muscle contraction
an adpation of muscle cells is that skeletal muscle cells fuse together during development to form
multinucleated cells that contract in unison
sperm cells diagram
sperm cell function
- reproduction, to fuse with an egg
- initiate the development of an embryo
- and pass on fathers genes
a sperm cell adaptations is that the head contains a
- nucleus
- that contains half the normal number of chromosomes
- (haploid, no chromosome pairs
a sperm cell adaptations is that the acrosome in the head contains
- digestive enzymes
- that can break down the outer layer of an egg cell
- so that the haploid nucleus can enter to fuse with the egg’s nucleus
a sperm cell adaptations is that
the mid-piece is packed with
- mitochondria
- to release energy (via respiration) for the tail movement
a sperm cell adaptations is that the tail rotates
- propelling the sperm cell forwards
- and allowing it to move towards the egg
root hair cell diagram
root hair cell function
absorption of water and mineral ions from soil
a root hair cell adaption is that is has root hair to
increase surface area (SA) so the rate of water uptake by osmosis is greater (can absorb more water and ions than if SA were lower)
a root hair cell adaption is that is has thinner walls than other plant cells so that
water can move through easily (due to shorter diffusion distance)
a root hair cell adaption is that is has a permanent vacuole contains
cell sap which is more concentrated than soil water, maintaining a water potential gradient
a root hair cell adaption is that is has mitochondria for
active transport of mineral ions
xylem vessel cell diagram
xylem cells lose their top and bottom walls to form
a continuous tube through which water moves from the roots to the leaves
xylem vessel cells function
transport tissue for water and dissolved ions
an adaption of a xylem vessel cell is that it has no top and bottom walls between cells to
form continuous hollow tubes through which water is drawn upwards towards the leaves by transpiration
an adaption of a xylem vessel cell is that it has dead cells without organelles or cytoplasm, to allow
free movement of water
an adaption of a xylem vessel cell is that it has outer walls which are thickened with a substance called
- lignin
- strengthening the tubes
- which helps support the plant
phloem vessel cell diagram
phloem vessel cell function
transport of dissolved sugars and amino acids
a phloem vessel cell adaption is that it is made of living cells which are supported by
companion cells
a phloem vessel cell adaption is that cells are joined end-to-end and contain
- holes in the end cell walls (sieve plates)
- forming tubes which allow sugars and amino acids to flow easily through (by translocation)
a phloem vessel cell adaption is that cells also have very few
subcellular structures to aid the flow of materials
epithelial cells in the small intestine are specialised to
absorb food efficiently
red blood cells are specialised to
transport oxygen
in multicellular organisms, specialised cells of the same type group together to form
tissues
a tissue is
a group of cells that work together to perform a particular function
epithelial cells group together to form
epithelial tissue (the function of which, in the small intestine, is to absorb food)
muscle cells (another type of specialised cell) group together to form
muscle tissue (the function of which is to contract in order to move parts of the body)
different tissues work together to form
organs
different organs work together to form
organ systems
animal and plant cells are types of eukaryotic cells, whereas bacteria are a type of
prokaryote
prokaryotic cells differ from eukaryotic cells in having a cytoplasm that
lacks membrane-bound organelles
prokaryotic cells differ from eukaryotic cells as their ribosomes are
structurally smaller (70 S) in comparison to those found in eukaryotic cells (80 S)
prokaryotic cells differ from eukaryotic cells as they have no nucleus, instead they have
- a single circular DNA molecule that is free in the cytoplasm
- and is not associated with proteins
prokaryotic cells differ from eukaryotic cells as they have
a cell wall that contains murein (a glycoprotein)
some prokaryotic cells have plasmids which are
small loops of DNA that are separate from the main circular DNA molecule
plasmids contain genes that can be
passed between prokaryotes (e.g. genes for antibiotic resistance)
some prokaryotes (e.g. bacteria) are surrounded by a final outer layer known as a
capsule (slime capsule)
a bacteria capsule helps to
- protect bacteria from drying out
- and from attack by cells of the immune system of the host organism
some prokayotes also have long, tail-like structure that rotate, enabling the prokaryote to move called a
flagellum
structures always present in prokayotics (5)
- cell wall
- cell surface membrane
- cytoplasm
- circular DNA
- ribosomes
structures sometimes present in prokayotics
- flagellum (motion)
- capsule (protection)
- infolding of cell surface membrane (may allow photosynthesis or carry out nitrogen fixation)
- plasmid (small circle of DNA)
- pili (for attatchment to other cells or surfaces, involved in sexual reproduction)
infolding of cell surface membrane in some prokaryotic cells does what
- may allow photosynthesis
- or carry out nitrogen fixation
the pili of some prokaryotic cells does what
- is for attatchment to other cells or surfaces
- involved in sexual reproduction
structures sometimes and always present in prokaryotic cells diagram
in prokaryotes their genetic material is not packaged within a
- membrane-bound nucleus
- and is usually circular
- (eukaryotic genetic material is packaged as linear chromosomes)
prokaryotes lack what type of
organelles
membrane-bound
prokaryotes are smaller than
eukaryotic cells
prokaryote ribosomes are structurally smaller
(70 S) in comparison to those found in eukaryotic cells (80 S)
genome of a prokaryotic cell
- DNA circular
- with no proteins
- in the cytoplasm
genome of a eukaryotic cell
- DNA is associated with histones (proteins)
- formed into chromosmes
cell division of prokaryotes
- occurs by binary fission
- no spindle involved
cell division of eukayotes
- occurs by mitosis or meiosis
- involves a spindle to seperate chromosomes
prokaryotic ribosomes are
70S
eukaryotic ribosomes are
80S
cell walls of a prokaryote is made of
- peptidoglycan (polysaccharide and amino acids)
- and murein
cell walls of a eukaryote is made of
- plants: cellulose or lignin
- fungi: chitin (similar to cellulose but contains nitrogen)
Prokaryotic & Eukaryotic Cells Comparison Table
viruses are
- non-cellular
- infectious particles
- that straddle the boundary between ‘living’ and ‘non-living’
virusesare relatively simple in structure, much smaller than
prokaryotic cells
structurally viruses have a nucleic acid core, their genomes are either
- DNA or RNA
- and can be single or double-stranded
structurally viruses have a protein coat called a
capsid
some viruses have an outer layer called an
envelope
some viruses have an outer layer called an envelope formed usually from the
membrane-phospholipids of a cell they were made in
all viruses are parasitic in that they can only reproduce by
- infecting living cells
- and using their protein-building machinery (ribosomes) to produce new viral particles
virus diagram
