Organelles of the cell

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  • Created by: sesims
  • Created on: 03-04-16 13:57

The Nucleus

  • DNA - contains chromosomes which are made up of DNA and protein (histones)
  • Nuclear envelope - separates nucleus from the cell, double membrane, controls substances moving in and out of the nucleus 
  • Nuclear pore - where the double membrane fuses, allows passage of substances (i.e mRNA, ribosomes) into the nucleus 
  • Nucleoplasm - contains chromatin
  • Nucleolus - site of formation of rRNA 
  • Structure/size - spherical, 10-20 micrometers 
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Mitochondria

  • Shape/size - cylindrical, 1-10 micrometers in size
  • Cristae - folds in the inner membrane, increases the surface area for the attachment of enzymes involved in respiration
  • Matrix - organic solution, containing lipids etc within cristae
  • Ribosomes/DNA - allow the mitochondria to self-replicate and produce some of their own proteins
  • Function - produce ATP for respiration - some reactions occur on the inner membrane, some in the matrix
  • Surface area - large surface area:volume ratio. Reduces diffusion distance from the edge to the centre of the organelle
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Ribosomes

  • Size - 70S in prokaryotes, 80S in eukaryotes
  • Structure - Large subunit and small subunit
  • Made from - rRNA and protein
  • Function - protein synthesis, site of translation
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Endoplasmic Recticulum

  • Structure - elaborate system of double membranes folded to form flattened sacs, interconnected and fluid-filled
  • Nuclear envelope - continuous with it allows the transport of substances
  • Smooth ER - lack ribosomes, associated with synthesis transporting lipids
  • Rough ER - ribosomes on its surface, transports protein made there
  • Present in cells making a lot of protein, e.g. glands
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Golgi Body

  • Structure - similar to ER but more compact
  • What happens? - vesicles containing polypeptides fuse with the Golgi body. Modifies and packages proteins and enzymes. Pinched off the other end 

Functions

  • modifying and packaging enzymes and proteins,
  • producing secretory vesicles containing enzymes and proteins
  • producing glycoprotein,
  • transporting and storing lipids,
  • forming lysosomes
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Centrioles

  • Structure - two microtubules making hollow cylinders at 90 degree angles
  • Location - just outside the nucleolus
  • Role - organise the microtubules that make spindle for which chromosomes attach to in cell division
  • Form a part of the paired structure that is a centrosome
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Vacuole

  • Role - supportive, contains cell sap, keeps the cell turgid which supports the plant
  • Structure - fluid filled sac bound by a single membrane (the tonoplast)
  • Cell sap - a mixture of glucose, amino acids, minerals and often mineral pigments
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Chloroplasts

  • Location - photosynthesising cells, especially mesophyll cells

Features:

  • Envelope - the chloroplast envelope surrounds each chloroplast
  • Stroma - fluid-filled, contains some products of photosynthesis
  • Ribosomes/DNA - allow the organelle to self-replicate
  • Thylakoid - flattened sacs containing photosynthetic pigment. When stacked, they're called 'granum' which can contain 2-200 thylakoids. Efficient arrangement providing a large surface area for trapping light energy
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Cell Wall

  • Structure - largely made of cellulose. Held together in microfibrils, in the polysaccharide pectin 
  • Transport - gaps between cellulose molecules made the wall fully permeable to minerals and dissolved ions. The apoplast pathway is the main way in which water crosses the root
  • Communication - plasmodesmata pass through pits. This is the symplast network, very important in water transport
  • Mechanical - laminated arrangement keeps the wall strong. Exerts pressure, allowing the cell to become turgid, giving the plant suppory
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