cell structure Flashcards
Convert 1m into mm
1000mm
how much is 1mm in micrometre
1000
How does 1 micrometre in nanometres
1000
What are the advantages of electron microscope over light microscope
- light microscope only a few structures are easily visible within the cytoplasm
- many more structures calleed organelles are visible in eukaryotic cells
- electron microscope uses electrons (rather than light) have much shorter wavelength so microscope has a greater magnification and higher resolving power
What are organelles
- specific roles within the cell
- are surrounded by a membrane
What do membranes in organelles do
- provide a large surface area for transport of molecules and attatchment of enzymes
What is the nucleus
- largest organelle present in cytoplasm of a eukaryotic cell
- contains DNA coding for protein synthesis
What does the nucleoplasm do
contains chromatin which condenses to form chromosomes during cell diviion
What surrounds the nucleus
- double membrane the oiter membrane which is continuos with the endolasmic reticulum surrounds it
- the membrane has pores that allow mRNA to leave nucleus
What does the nucleolus do
- small spherical body found within the nucleus
- resposible for the production of rRNA and ribosomes
What is the role of mitochondria
- site of aerobic respiration
- producing ATP
What is the structure of mitochondria
- folded into structures called cristae which provide a large surface area for the attatchment of enzymes eg ATP synthetase
- a fluid filled matrix contains lipids and proteins
- 70s ribosomes and a small circle of DNA
Where are high numbers of mitochondria found
- metabolically active cells
- muscles and liver
where are chloroplasts found
found in photosynthetic plants
What is the role of chloroplasts
site of photosynthesis
What is the structure of chloroplasts
- organelle surrounded by a double membrane and contains a fluid filled stroma with starch grains , 70 s ribosomes and a circle of DNA
- thylakoid is flattened membrane
- stacks of thylakoids contain photsynthetic pigments which include chlorophyll
what are endoplasmic reticulum
- system of double membranes that form interconnected flattened fluid filled sacs called cristernae connected to nucelar envelope
What is the role of endoplasmic reticulum
transport of materials through the cell
What is the structure of rough endoplasmic reticulum and function
- ribosomes attatched to the outer surface
- once proteins have synthesised at ribosomes they are transported via cristernae
What is the structure and function smooth endoplasmic reticulum
- lacks the ribosomes and is involved with the synthesis and transport of lipids
What are ribosomes made of
- rRNA and protein
where are ribosomes found
cytoplasm
What is the role of ribosomes
assembly of proteins during translation
What is the structure of ribosomes
- consisting of two subunites the small subunit contains a mRNA attatchment site and the large subunit two tRNA attatchment sites
What are the differences of sizes in ribosomes
- eukaryotic cells - 80s - larger
- prokaryotic cells - 70s - smaller
What is the golgi body
- stack of curved cristernae
What is the role of the golgi body
- vesicle containing polypeptides budd off the rough endoplasmic reticulum and fuse of the golgi
- proteins are modified and packaged into vesicles by golgi body for exxport
- also involved in transport and stroafe of lipids and production of glycoprotens and lysosomes
What are lysosomes
- small single membrane bound vacuoles that are pinched off from the golgi body containing digestive enzyme lysozyme
What is the role of lysososmes
- role is to digest worn out orrganelles within the cell and foreign material that has been engulfed by phagocytosis ef bacteria engulfed by a white blood cell
What are centrioles where are they found
- animal cells and protoctitians
- noticabley absent from higher plants
- consist of two rings of microtubules at right angles to each other they organise the microtubules that make the spindle during cell division
What are vacoules
- within plant cells large central vacoule surrounedd by tonopolast
- main function of vacoule is in supporting soft plant tissues but also store chemicals such as glucose and amino acids in cell sap
What is the cell wall made up of in plants
cellulose
What is the cell wall in bacteria made up of
peptidoglycan
what is the cell wall in fungi made up of
chitin
What is the cell wall important in
- providing strength to the cell wall which resists the expansion of the vacuole due to osmosis creating turgor and support for non woody plants
- transport of water and dissolved molecules and ions through gaps in the cellulose fibres known as the apoplast pathway
- communication between cells via pores in the cell wall which allow strands of cytoplasm called plasmodesmata to pass allows water to pass via the symplast pathway
What are the differences between plant and animal cells
plant cell
* cell wall surrounding a membane
* chloroplast present (in cells above ground)
* large permanent single central vacoule
* no centrioles
* plasmodesmata
* starch grains used for energy storage
animal cells
* no cell wall membrane only
* chloroplasts never present
* small temporary vacoules
* centrioles
* no plasmodesmata
* glycogen granules used for energy storage
what are prokaryotic cells eg bacteria and there structure
- simplest and oldest cells on earth
- lack a true nucleus instead posessing DNA loose within the cytoplasm and have no membranous organelles though some have infoldings of the membrane called mesosomes where respiration is thought to occur
- the cell wall is made from peptidoglycan and the ribosomes are slightly smaller than those of eukaryotes at 70s
- some bacteria contain plasmids (small rings of DNA) that contain antibiotic resistance genes
what are viruses
- don’t posess a cytoplasm, organelles or any chromosomes
- core of nucleic acid (DNA or RNA) surrounded by a protein coat called the caspid
what are examples of viruses
- examples inclue tobacco mosaic virus cause tobacco mosaic disease and HIV causes HIV-AIDS
how does a virus reproduce
- inert ‘virion’ incapable of reproducing or synthesising proteins without the use of a host’s cytoplasm
- it is when they burst out of cells and reinfect healthy cells that damage occurs
what is the formula for magnification
- size of image/size of object
organelle
- a specialised structure found within eukaryotic cells that carries out a specific function for the cell
eukaryotic cells
- eukaryotes contain DNA in chromosomes in a nucleus and posess membrane bound organelles eg plants and animals
resolving power
- the minimum distance by which two points must be seperated in order for them to be seen as two distinct points rather than a single focused image
prokaryotes
a single celled organism lacking membrane bound organelles such as a nucleus with its DNA free in the cytoplasm
magnification
how many times bigger the image is compared to the object
tissue
a group of cells working together with a common structure and function
organ
a group of tissues in a structural unit working together and performing a specific structure
Why are levels of organisation important
- multicellular organisms need to possess specialised cells that form tissues and organs to do this
- single celled organisms carry out all life processes within one cell
What are the role of stem cells
- undifferentiated (non specialised cells) in the embryo that can differentiate to form any tissue
What are the four main types of tissue in mammals
- nervous
- connective
- muscle
- epithelial
What is connective tissue
- supports, connects and seperates the different tupes of tissues and organs of the body
- cells are contained within an extracellular fluid or matrix and may be surrounded by elastic or collagenous fibres eg tendons and blood
What are the three types of muscle tissue
- skeletal
- smooth
- cardiac muscle
What is the skeletal muscle
bands of long cells or fibres giving powerful contraction and is used for locomotion in mammals
What is smooth muscle
- individual spindle shaped cells which contract rythmically but are not powerful so they are found in the walls of blood vessles, digestive and respiratory tracts
What is cardiac muscle
- stripes but lack long fibres
- they contract rythmically and with some force
- don’t tire easily
What is epithelial tissue
- covers and lines the body eg lining the intestines and trachea and covers our body as part of our skin
- all epithelal cells sit on a basement membrane but cells do vary in shape and complexity
What are the three types of epithelial cells
- simple cubodial
- columnar
- squamous epitherlium
what are simple cubodial epithelium
- cells cube shape
- tissue one cell thick
- lining kidney tubules and ducts of glands
What is columnar epithelium
cells are more rectangular may have cilia present eg lining the trachea
what are squamous epithelium cells
- consists of flattened cells
- found in alveoli and lining arteries
What are the level of organisation from smallest to largest
- cells
- tissues
- organs
- organ systems
What is an organ systems
- group of organs working togeether with a particular role
What is the digestive system made up of
- stomach
- ileum
- colon
What is the circulatory system consist of
- heart
- arteries
- capillaries
- veins
