Cell Structure & Organisation
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- Created by: Kirsty_hodnett
- Created on: 06-04-15 14:13
Nucleus & Mitochondria
- control the cells activities and retain the chromosomes
- most prominant feature in the cell
- bound by double membrane called nuclear membrane/envelope
- outer membrane is continuous with endoplasmic reticulum
- pores allow passage of large molecules out of nucleus
- granular nucleoplasm contains genetic material chromatin- coils of DNA bound to protein
- nucleolus manufactures RNA to make ribosomes
Mitochondria
- sites of aerobic respiration, produces energy carrier molecule ATP
- double membrane separated by fluid filled intermembrane space
- inner membrane folded inwards forming cristae
- organic matrix contains chemical compounds including DNA to control its own protein production
- cristae provide large surface area
- muscle cells have large numbers of mitochondria
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Endoplasmic Reticulum
- elaborate system of parallel double membranes forming flattened sacs
- fluid spaces inbetween are cisternae
- connected to nuclear membrane
- interconnection allows for transport of materials throughout cell
rough ER
- ribosomes on outer surface
- transports proteins made by the ribosomes
- present in cells that make enzymes
smooth ER
- membranes lack ribosomes
- syntheisises and transports lipids
liver cells and secretory cells have many ER
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Ribosomes & Centrioles
- found in both prokaryote and eukaryote cells
- smaller in prokaryotes
- occur singly in the cytoplasm or associated with rough ER
- one large and one small sub unit
- manufactured in the nucleus from ribosomal RNA and protein
- synthesise proteins
centrioles
- found in all animal cells and most protoctists
- located just outside nucleus in the centrosome
- hollow cylinders at right angles to eachother
- centrioles divide during cell division
- syntheisise microtubules of a spindle
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Golgi Body & Lysosomes
- compacter version of the ER
- formed by rough ER being pinched into vesicles which fuse into the golgi body
- proteins in the vesicles can then be modified and packaged
- golgi body can be pinched off into vesicles again and the products secreted
- other functions are: producing secretory enzymes, secreting carbs, producing glycoprotein, transporting and storing lipids, forming lysosomes.
lysosomes
- small vacuoles formed when vesicles are pinched off the golgi body
- contain and isolate potentially harmful digestive enzymes
- can also release these to destroy old organelles
- lysosomes discharge their contents into vacuoles
- can also digest material brought into the cell
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Organelle Interrelation
- functions of organelles within the cell are often linked
- ribosomes produced in nucleolus take up position on the rough ER
- pores in nuclear membrane allow mRNA molecules to leave nucleus and attach to ribosomes on rough ER
- protein synthesis occurs on the ribosomes making proteins in primary form
- these polypeptides are then modified in the golgi apparatus into their tertiary structure
- these enzymes are packaged into secretory vesicles and transported to the membrane to be secreted
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Chloroplasts & Vacuole
- chloroplasts are found in the cells of photosynthesising tissue
- surrounded by double membrane
- stroma- fluid filled with ribosomes, lipid, circular DNA and starch grains
- thylakoids- flattened sacs stacked to form granum
- chlorophyll is found in the thylakoids
- the arrangement provides a large surface area for trapping light
vacuole
- in plants this is large and permanent
- fluid filled sac with a single membrane called he tonoplast
- storage site made of cell sap to store chemicals e.g glucose
- provides an osmotic system to support young tissues
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Cellulose Cell Wall
- consists of cellulose microfbrils embedded in a polysaccaride matrix
- fully permeable to water and substances in solution
- cell wall can withstand the vacuole pushing against it, reaching a state of turgor
- cellulose microfibrils are very strong providing mechanical strength
- cells can connect through pores where plasmodesmata can pass, enabling exchange of materials
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Differences Between Plant & Animal Cells
Plant Animal
- cell wall surrounds membrane
- no cell wall, membrane only
- chloroplasts present
- no chloroplasts
- single large permanent central vacuole filled with cell sap
- small temporary scattered vacuoles
- no centrioles
- centrioles
- plasmodesmata
- no plasmodesmata
- starch grains used for storage
- glycogen granules used for storage
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Differentiation & Specialisation
- single celled organisms carry all life functions out within a single cell
- multicellular organisms need specialised cells to carry out particular functions
- each cell becomes specialised in structure to suit its role
- some cells remain undiffereniated as 'packing' cells
- other cells can differentiate in a number of ways:
- shape- nerve cells elongate
- numbers of organelles- cells carrying out photosynthesis need more chloroplasts
- contents of cell- red blood cells are packed with haemoglobin
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Tissues->Organs->Systems-:>Organisms
tissues:
- Cells that differentiate in the same way
- a collection of specialised cells of the same type working together to carry out a particular function
organs:
- a part of the body that carries out a structural and functional unit made from more than one tissue
systems:
- a collection of organs that carry out a particular function
organisms
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Tissues->Organs->Systems->Organisms
tissues:
- Cells that differentiate in the same way
- a collection of specialised cells of the same type working together to carry out a particular function
organs:
- a part of the body that carries out a structural and functional unit made from more than one tissue
systems:
- a collection of organs that carry out a particular function
organisms:
- all of the systems of the body working together
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Differences Between Prokaryote & Eukaryote Cells
Prokaryote Eukaryote
- found in bacteria and blue/green algae
- found in plants, animals, fungi and protoctists
- no membrane bound organelles
- membrane bound organelles
- ribosomes are smaller
- ribosomes are larger
- DNA lies free in cytoplasm
- DNA located on chromosomes
- no nuclear membrane or ER
- distinct membrane bound nucleus
- cell wall containing murein
- cell wall in plants of cellulose
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Viruses
- unusual life form
- extremel small
- 'non cells'- no cytoplasm, organelles or chromosomes
- outside a living cell they are a virion
- when inside a host they take over the cells metabolism and multipy within it
- each virus particle has a core of nucleic acid surrounded by a capsid protein coat
- most viruses are found in animal cells
- those attacking bacteria have DNA
- animal and pant viruses have RNA
- they cause a variety of diseases
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