2.1.1 cell structure Flashcards
define: eukaryotic organisms
multi-cellular organisms made of eukaryotic cells e.g. animal and plant cells
define: prokaryotic organisms
single-celled organisms made from prokaryotic cells e.g. bacteria
function of cytoskeleton
- providing mechanical strength to cells
- aiding transport within cells
- enabling cell movement
function of intermediate fibers
gives strength to cells and helps maintain integrity
function of microfilaments
fibers are made from the protein, actin responsible for movement of the cell and cytoplasm during cytokinesis
function of microtubules
- formed by the globular protein, tubulin polymerise to form tubes that determine the shape of the cell
- act as tracts for organelles moving around the cell forms organelles like centrioles and cilia
function of microvilli
- found in specialised animal cells
- used to increase surface area of cell surface membrane to increase rate of exchange of substances
function of mitochondria
- site of aerobic respiration
- as a result of respiration, they release ATP (energy carrier in cells)
function of nucleus
- controls all the activity of the cell
- where the genetic code (DNA) of the cell is stored, replicated and copied into RNA (transcribed) the nucleus is attached to the rough ER so the mRNA can easily get to ribosomes
function of ribosomes
- protein synthesis (where proteins are made)
- assemble amino acids into proteins in chains using mRNA
function of rough endoplasmic reticulum
site of protein synthesis
function of smooth endoplasmic reticulum
responsible for carbohydrates and lipid synthesis and storage
structure of microtubules
- found in eukaryotic cells
- makes up cytoskeleton of cell
- made of α and β tubulin combined to form dimers which join to protofilaments
structure of microvilli
cell membrane projections
structure of mitochondria
- oval shaped
- surrounded by two
membranes (double membrane) - the inner membrane forms finger-like structure called cristae which increases the surface area
- the solution inside is called a matrix which contains enzymes for respiration
- mitocondrial DNA - small amounts of DNA, enable mitochondrion to reproduce and create enzymes
structure of ribosomes
- a 2 subunit organelle
- made from RNA and protein
- not membrane bound
- very small organelles (around 22nm in diameter)
- found free floating in the cytoplasm or attached to the RER
- 80S ribosomes => eukaryotic cells
- 70S ribosomes => prokaryotic cells, mitochondria and chlorplasts
structure of rough endoplasmic reticulum
- stacks of membrane bound (fluid filled) sacs which form sheets called cisternae
- attached to the nucleus and covered with ribosomes
- consists of an interconnected system of flattened sacs
structure of smooth endoplasmic reticulum
similar to RER but lacks ribosomes - a system of interconnected tubules
what are nuclear pores?
allows molecules to enter (e.g. nucleotides for DNA replication) and leave the cell e.g. mRNA leaves the cell
what are the 3 structural components to the cytoskeleton?
microfilaments
microtubules
intermediate fibers
what is chromatin?
the DNA (with associated histone proteins) contains the genetic code which controls the activity of the cell
what is the double nuclear envelope?
a double membrane which compartmentalises the nucleus and prevents damage and protects the DNA
what is the nucleolus?
site of ribosome production
composed of RNA and proteins
function of cell-surface membrane
- regulates the movement of substances into and out of the cell
- contains receptor molecules which allow it to respond to chemicals like hormones
function of cellulose cell wall
- gives the plant mechanical strength
- gives the plant cell support and its shape
- contents of the plant cell can ‘push’ against cell wall (turgid cell) - gives the cell and whole plant good support
function of centrioles
makes a copy of itself during cell division and then helps to form the spindle in cell division
function of chloroplasts
- photosynthetic reactions
- contains chlorophyll
- light-dependent stage takes place in the thylakoids
- light-independent stage takes place in stroma
function of cilia
- sensory function (e.g. nose), beat creating a current to move fluid/mucous/objects
- for locomotion
- allows the movement of substances over the cell surface
function of flagella
- whip-like - enables a cells mobility
- the microtubules contract to make the flagellum move
- propel cells forward e.g. sperm cell
function of golgi apparatus
- allows internal transport
- receives proteins from the RER
- modifies and processes molecules (such as new lipid and proteins) and packages them into vesicles
- these may be secretory vesicles (if the proteins need to leave the cell) or lysosomes (which stay in the cell)
- makes lysosomes
- lipid synthesis
function of large permanent vacuole
- stores cell sap
- support herbaceous plants by making cells turgid
- helps maintain shape and gives support by maintaining turgor pressure
- sugars and amino acids act as a temporary food store
function of lysosomes
- contain powerful hydrolytic digestive enzymes known as lysozymes
- their role is to break down worn out components of the cell or digest invading cells
structure and function of vesicles
- found in plant and animal cells
- a membrane-bound sac for transport and storage
structure of cell-surface membrane
- the membrane found of the surface of animal cells and inside the cell wall of plant and prokaryotic cells
- a phospholipid bilayer
- composed of proteins and lipids
structure of cellulose cell wall
- made of beta-cellulose microfibrils - complex carbohydrates
- cell wall is fully permeable to substances
- thin layer called the middle lamella which marks the boundary between adjacent cell walls and ‘cements’ adjacent cells together
structure of centrioles
- a component of the cytoskeleton composed of many microtubules
- small, hollow cylinders that occurs in pairs next to the nucleus in animals cells only
- each centriole contains a ring of 9 microtubules
structure of nucleus
- consists of a double-layered nuclear membrane or envelope that separates the nucleus from the cytoplasm
- connected to endoplasmic reticulum
structure of chloroplasts
- larger than mitochondria
- surrounded by a double membrane
- membrane-bound compartments called thylakoids contain chlorophyll
- thylakoids stack to form grana
- contains small circular DNA and ribosomes used to synthesise proteins needed in chloroplast replication and photosynthesis
structure of cilia
- hair-like extensions that protrude from some animal cell types
- in cross section, they have an outer membrane and a ring of nine pairs of protein microtubules inside with two microtubules in the middle
- known as a 9+2 arrangement
- arrangement allows movement
structure of flagella
- similar to cilia but longer
- they protrude from the cell surface area and are surrounded by the plasma membrane
- 9+2 arrangement
structure of golgi apparatus
- stacks of flattered, membrane bound sacs (cisternae)
- these are continuously formed from the ER at one end and budding off as golgi vesicles at the other
structure of large permanent vacuole
- single membrane bound (membrane called tonoplast)
- contains a fluid called cell sap (solution of mineral salts, sugars, amino acids, wastes etc)
- selectively permeable barrier
structure of lysosomes
they are spherical sacs surrounded by a single membrane
magnification equation
image size = actual size x magnification
define resolution
Resolution is the ability to distinguish between objects that are close together (i.e. the ability to see two structures that are very close together as two separate structures)
define magnification
Magnification tells you how many times bigger the image produced by the microscope is than the real-life object you are viewing
different types of microscopes
light
electron
laser scanning confocal