Cell Biology - Outcome 1 Flashcards
Structure and Function of the Cell Membrane and Eukaryotic Organelles
what is the definition of a prokaryote ?
does not have true nucleus
what is the definition of a eukaryote?
has a true nucleus
what is the definition of unicellular?
single-celled organism
what is the definition of multicellular?
multi-celled organism
what is the definition of an organelle?
membrane-bound component of cell that performs specific function
what type of organism contains no membrane-bound organelles?
prokaryotes
which organism is bigger in size, eukaryote or prokaryote?
eukaryote is bigger in size and prokaryote is smaller in size
what type of organism DOES contain membrane-bound organelles?
eukaryotes
what do eukaryotes contain, and where is it contained?
membrane-bound nucleus, contains multiple chromosomes which are contained within nucleus
what does NOT exist in eukaryotes?
plasmids
eukaryotes can be what?
single-celled or multi-celled
what is an example of a prokaryote?
bacteria
what is an example of a eukaryote?
animal cell, plant cell and fungi
eukaryotes contain internal membranes in forms of what?
organelles
what do cells need to survive? and what must it all remove?
it needs oxygen, water and energy to survive and it must also remove carbon dioxide as a waste material.
how can cells exchange materials?
with the environment
what happens if the cell does not exchange materials efficiently?
cell will be deprived of oxygen and nutrients, it will then become poisoned from build up of toxic waste materials
what is the cell membrane composed of?
lipids and proteins
what is the cell membrane classed as?
semi-permeable
what is the function of the cell membrane?
controls what enters and exits the cell
what does the nucleus contain and in what form?
contains genetic material (DNA) in the form of chromatin
what happens to chromatin in cell division?
it organises itself into sets of chromosomes
what is the nucleus bounded by and what does it create?
double inner membranes, the outer and inner membrane which fuse at certain points to create nuclear pores
what are nuclear pores necessary for?
transport of materials in and out of nucleus
what is the structure within the nucleus called and what is its function?
nucleolus, a sub-organelle where ribosomes are assembled
what is the mitochondrion the site of?
energy production/respiration
what is cristae and what does it provide?
folded inner-membrane that creates finger-like projections, provides increased surface area for chemical reactions
what does the mitochondrion provide?
an environment for the conversion of nutrients into adenosine triphosphate (ATP)
what is the endoplasmic reticulum (ER)?
a series of interconnected flattened membranes within the cytosol where its surface can be embedded with ribosomes or not
what is the rough endoplasmic reticulum (RER)?
a part of the ER where ribosomes are attached and that it is involved in protein synthesis.
what happens when a protein is synthesised?
it is imported into the RER, assembled and folded and is then sent to the Golgi apparatus.
what is the smooth endoplasmic reticulum (SER)?
a part of the ER where no ribosomes are attached and is not involved in protein synthesis
what is the function of the SER?
site of lipid and steroid (fats and hormones) synthesis and detoxification of poisons
what is the Golgi apparatus?
series of membrane sacs
what happens at the Golgi apparatus?
proteins are modified and packaged here
what happens when a protein matures at the Golgi apparatus?
mature protein ‘buds’ off Golgi and is packaged into Golgi vesicle, which is then taken to cell membrane for secretion
what happens when the Golgi vesicle is at the cell membrane?
vesicle fuses with cell membrane and protein is secreted by exocytosis
how does a protein move through the cell?
in co-ordinated steps, moving from one organelle to another until it becomes a mature protein
what happens if a protein is coded for a location elsewhere in the body?
it is secreted by the synthesising cell
what is the secretory pathway?
passage from the RER to the cell membrane
what are lysosomes and what do they contain?
small membrane-bound sacs that contain digestive enzymes called lysozymes
what is the function of a lysozyme?
to break down foreign materials/damaged cells
what is the pH of a lysosome?
pH 2
what are peroxisomes?
oxidative organelles that use oxygen molecules to form hydrogen peroxide
what are peroxisomes involved in?
detoxification of poisons eg. alcohol
involved in breakdown of fatty acid chains
what is the cytoskeleton?
structural component of a cell
what does the cytoskeleton provide and what is it provided by?
provides internal support and this is provided by protein fibres of the cytoskeleton
what are the 3 types of protein fibres of the cytoskeleton?
- microfilaments (actin)
- intermediate filaments
- microtubules
what are microfilaments (actin) involved in?
cell division
what do intermediate filaments provide?
tensile strength and anchorage
what are microtubules involved in?
- being a set of tracks for newly synthesised proteins
- creation of spindle fibres during cell division
what is the overall function of the cytoskeleton?
- maintaining cell shape
- co-ordinating cell division
- cell movement
- organisation of organelles
what may eukaryotic cells have?
flagella
what is flagella made of?
microtubules
what are microtubules composed of?
the protein tubulin
what organelle is found in plant cells but NOT animal cells?
cell wall
what is a fungal cell wall composed of?
chitin
what is a plant and algal cell wall made of?
cellulose
what is a bacterial cell wall made of?
peptidoglycan
what is the function of the cell wall?
provides mechanical protection and is freely permeable
what is the function of chloroplasts?
site of photosynthesis
what is the equation for photosynthesis?
carbon dioxide + water + light energy -> oxygen + glucose
what green pigment is used to trap sunlight so that plants can photosynthesise?
chlorophyll
what is a plant vacuole?
a membrane bound sac within the cytoplasm
how much space does a plant vacuole take up?
80%
what is a plant vacuole filled with?
cell sap and water
what is the function of a plant vacuole?
maintains plant cell turgor pressure which is necessary to support plant and keep it upright
animal cells also have vacuoles, but what are their functions?
temporary storage of materials and transport of materials
how does the cell membrane separate contents from surrounding environment?
by forming a permeability barrier between all contents and extracellular environment.
what molecules does the cell membrane allow to move in and out freely?
respiratory gases
how does the cell membrane transport ions and glucose across membrane
by requiring mechanisms in the form of proteins
the cell membrane is said to be selectively permeable, what does this mean?
- controls what goes in and out
- controls what direction they move in
- maintains constant internal environment
- forms water insoluble barrier between ER and IR
what is the most abundant cell in the cell membrane?
phospholipids
what are phospholipids?
viscous solvents where proteins can be inserted/attached/integrated.
composed of 2 FA hydrocarbon chain attached to glycerol molecule and with phosphate group bonded to carbon no.3 on glycerol molecule by ester bond
what does amphipathic mean?
they have both polar and non-polar groups
how are phospholipids organised in the bilayer?
with their hydrophobic tails facing each other
creates barrier between aqueous cell contents and aqueous environments ie. stops free movement of water
what are phosphoglycerides?
phospholipids with additional amino acid group
what is sphingolipid in the membrane known as?
sphingomyelin
what are sphingomyelin involved in and what cell are they most abundant in?
neuron cells
what is sphingomyelin composed of?
1 FA tail which is parallel to the sphingosine tail where the phosphate group is attached
what is linked to the phosphate group in sphingomyelin?
a choline molecule that forms the head of the molecule
what is attached to a glycolipid?
a carbohydrate group
how is the carbohydrate group in a glycolipid bonded to the lipid component?
via glycosidic bond
what is the purpose of a glycolipid?
to stick out from the membrane and serve as markers for cell recognition
what is cholesterol?
another type of lipid found in the membrane
how many cholesterols are there per phospholipid in the membrane?
1
what type of membranes do not contain cholesterol?
bacterial membranes
how does cholesterol affect the permeability of the cell membrane to small water-soluble molecules?
they decrease the permeability
what would happen if there was no cholesterol in the membrane?
cells would need a cell wall
what does the amount of cholesterol determine?
how rigid the membrane will be
how can lipids move within the membrane?
- laterally (sideways)
- transversely (‘flip-flop’ across membrane
what does the composition of a membrane determine?
how much the membrane can move (fluidity)
what factors affect fluidity of the membrane?
- temperature
- cholesterol content
- saturation
how does temperature affect fluidity of membrane ?
decreased temperature means less energy for phospholipids
phospholipids stay more compacted
decrease fluidity
increased temperature means more energy for phospholipids
phospholipids move around more
increased fluidity
how does cholesterol content affect fluidity of membrane?
without cholesterol, membrane would be too fluid and would be at risk of leaking, reducing the barrier
cholesterol inserts itself between FA tails of lipid molecules, this decreases phospholipid movement making membrane more rigid, decreasing fluidity
how does cholesterol content affect membrane fluidity when put with low temperature?
cholesterol stops hydrocarbon tails crystallising (freezing), this helps maintain and increase fluidity
how does saturation affect membrane fluidity?
FA tail of phospholipids may be straight or ‘kinked’, this is determined by carbon bonds
saturated FA have no carbon to carbon double bonds (only single bonds), making the tail appear straight
unsaturated FA have one or more carbon to carbon double bond, making tail appear kinked
what happens in unsaturated phospholipids and what does it result in?
the kink in fatty acid tail increases the space between phospholipid molecules, more space to move around through membrane, more fluid
results in a thin, fluid liquid solution
what happens in saturated phospholipids and what does it result in?
the straight fatty acid tail results in lipid being able to be more compacted together, less space to move around through membrane, less fluid
results in more viscous liquid solution
describe the main points on the importance of membrane fluidity
- to adjust to the surrounding environment
(may have to adapt shape in order to fit a space)
(may have to adapt in response to pressure) - allows membrane to be quickly repaired if damaged
- can move to allow entry and exit of ions
- has ability to merge with organelle membranes
what are the three main types of membrane proteins?
- transmembrane
- peripheral
- integral
what are the features of a transmembrane protein?
- cross membrane completely
- may span it once or several times
- region embedded into membrane is hydrophobic with a-helice formation
- a-helice formation will be linked by hydrophilic regions which protrude into extracellular or intracellular environment
what are the features of an integral protein?
- embedded into the membrane
- do not span membrane completely
what are the features of a peripheral protein attached on the outside cell surface?
- becomes part of extracellular matrix (connective tissue)
- surrounds and supports cells
what are the features of a peripheral protein attached on the inside cell surface?
- protein becomes part of cytoskeleton
what are the functions of membrane proteins and describe them?
transport
- moving materials in and out (through pores or by forming pumps)
receptors
- allows cell to respond to its environment
- convey messages from outside the cell to inside cell
cell markers
- each organism has own unique ones which helps immune system to identify invaders
membrane composition varies between cell types, what are some examples of this?
- white blood cells have high amount of proteins which act as cell markers and receptor
- neuron cells have higher sphingomyelin content in their membranes
- the more saturated lipids, more fluidity
