Animal cell Plant cell
*Irregular in shape *have cellulose cell wall
*centrally placed nucleus *are regular in shape
*have temporary vacuole *have chloroplast
*have centrioles *have nucleus on the side
*storage in form of glycogen *central permanent vacuole
*animal cell are 20 micro meter *have plasmodesma
*storage in form of starch
*plant cell are 40 micro meter
Organelles:
-Single membrane bond -Double membrane bond
1- endoplasmic reticulum (rough & smooth) 1- mitochondria
2- ribosomes 2- chloroplast
3- golgi apparatus 3- nucleus
4- vesicles
Additional stuffs:
plant: animal:
cell wall centrioles
vacuole
tonoplast + cellsap
DOUBLE MEMBRANE STRUCTURES:
1- Nucleus: (allows exit of MRNA)
- controls all activities of cell including cell division
- double membrane bond
- 10 micro meter on average size
- outer membrane of the nucleus is merged up with Rough Endoplasmic Reticulum- inner membrane is continuous
- nuclear pores are gaps, present in nuclear membrane which are meant for exchange of materials between cytoplasm and nucleus itself
- the nucleic acids and other important molecules needed in synthesis of polymers move into the nucleus while ribosomes and MRNA move out into the cytoplasm
- there is one or more nucleoli which synthesis ribosomal units and nucleic acids
- nucleolus contains ribosomal units, protein and nucleotides
- size of nucleolus is 2 micro meter. At x2800 magnification its size is 2.5 micro meter
- nucleoli: formation of ribosomes
- chromatin is present inside the nucleus which are loosened strands of DNA
- chromosomes or chromatin contains genes which control different trails or features of the body
2- Mitochondria: (allows oxygen to enter)
- average size is 1-5 micro meter- has 2 membranes
- outer one is continuous
- inner one has infoldings
- space between inner and outer membrane is called "inter membrane space"
- while the inner space is called "matrix"
- inner membrane has cristae, which are stalk like
- the bulb like portion of stalk is called ATP synthase
- it has 70-s ribosomes
- it has circular DNA of its own, so it can divide on its own and change its shape as well
- mitochondria is the only organelle whose activity is not controlled by nucleus (and chloroplast)
- function of mitochondria is
1. aerobic respiration
2. release of energy
3. synthesis of energy
4. synthesis/ production of ATP
3- Chloroplast: (allows carbon dioxide to enter)
- double membrane organelle
- it is meant for 2 kinds of reactions- one is from light energy to ATP
- second is from ATP to glucose (chemical energy)
- second largest organelle after nucleus in plant cell
- the size ranges from 5-8 micro meter
- has a disk shape
- stroma contains a solution of different protein, starch grains and ribosomes 70-s
- there are enzymes present who are responsible for "light independent stage"
- there are stacks of tthylakoid membrane arranged in a form of granum which surround chlorophyll
- function of granum is to perform light independent stage of photosynthesis
- chloroplasts have their own circular DNA which controls the activity as well as the protein synthesis inside it so they can divide on their own as well
- chloroplast move through the cytoplasm along the cell wall for maximum exposure to light
SINGLE MEMBRANE STRUCTURE
1- Endoplasmic Reticulum:
*system of flattened sac enclosing the spaces called "cisternae"
*there are 2 types of endoplasmic reticulum: 1- rough ER 2- smooth ER
(i) Rough endoplasmic reticulum: (protein synthesis)
- found in continually with the other membrane of the nuclear envelope
- the membrane of RER is rough due to the presence of 80-s ribosomes studded on them
- it secrets enzyme
- its function is packaging and modification of polypeptide chain which have been synthesized on the ribosomes
-apart of the RER then buds off to form a vesicle containing the protein and moves it to golgi apparatus
(ii) Smooth endoplasmic reticulum: (lipid synthesis)
- it is located distant from nucleus
- it is smooth as it doesn't contain ribosomes
- it has nothing to do with protein synthesis
- it is involved in lipid metabolism fro example: synthesis of cholesterol and reproductive hormones, like oestrogen
- synthesis of steroids
2- Ribosomes:
- 80-s ribosomes are present in Eukeryotic cells, free in cytoplasm as well as attached to RER- made from 2 subunits
- these units are synthesized in the nucleolus which then arrange with each other
- they pass from nucleus to cytoplasm through nuclear pores
- they contain ribosomal proteins, R-RNA and M-RNA (messenger RNA)
- function is to synthesize polypeptide chains with specific aminoacid sequence as coded by messenger RNA
- the polypeptide formed then is passed into RER
3- Golgi apparatus:
- is made up of isolated flattened sac of cisternae
- function is processing of proteins
- proteins made up of ribosomes are packaged by RER, which then transport in a vesicle to become a part of golgi body- on the other end golgi body keeps on making golgi vesicles which contain processed proteins
- these proteins can be used inside the cell or be secreted outside the cell
- the processing involves adding on different compounds or molecules to the proteins for example,
if lipids are added they form lipoproteins or glycoproteins when carbohydrate chains are added on to the protein structure
- goblet cells has the most golgi apparatus
- nucleic acid is absent
4- Vesicle and lysosomes:
(vesicle transports enzyme) (lysosomes contain enzyme)
- are temporarily formed and contain transport materials
- they can be of different sizes varying from average 0.5- 1 micro meter- a vesicle can be a secretary vesicle if it carries a protein or lipid to be secreted out of the cell
- if it buds off the golgi apparatus then it is called the golgi vesicle
- if a vesicle contains lysosome (a hydrolytic enzyme) it is called a lysosome
- lysosome are involved in phagocytosis and antolysis
5- Centriole:
- there is a pair of centrioles only present in animal cell
- the 2 centrioles lie perpendicular to each other close to the nucleus- they are formed from a collection of micro tubules which are 0.4 micro meter in length placed in a 9x3 arrangement
- they contain a protein called tubulin
- their function is to arrange spindle fibres at the start of nuclear division
- only in plant cell
- contains cellulose fibres and other compounds
- cell wall of 2 adjacent plant cells stick together because of middle lamela
- at certain point cell wall is missing between 2 cells leaving a gap is called plasmodesma (plural= plasmodesmata)
- cytoplasmic bridges form through them which helps in transport and exchange of materials
7- Cell membrane:
- made from phospholipid molecules arranged as a bi-layer
- it is partially permeable, which means small particles and non-polar particles can cross through it while the charged particles are restricted
8- Vacuole:
- permanent organelle of plant cell
- made up of tonoplast, which contains a dilute solution of salts, sugar and other excretory matter
- vacuole maintains plant cell shape and turgidity
- also helps plant call to grow
- contains enzyme
Q- Explain the synthesis of insulin until it is secreted out of B- cell
A- Insulin is a protein made from polypeptide chains on ribosomes. it is then passed to RER where it is packaged and modified. from RER it is then taken into the golgi apparatus where it is processed. a golgi vesicle then buds off and takes it to the plasma membrane where it merges with it and then it is secreted out through the secretory vesicles
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