cell structures

• Cells

  Made of molecules, like amino acids, simple sugars and fatty acids, that enter the cell

  Internal structures that perform specialised functions -- organelles

  Smallest structural and functional unit of a living organism -- building blocks of life
• Organelles

  Membrane-bound compartments within the cell -- have different functions that keep the cell alive
• Nucleus

  Contains cell's genetic information -- needed for growth, repair, and proper functioning

  Control centre -- tells the rest of the cell what it's doing

  Nuclear membrane with nuclear pores
• Nucleolus

  In the nucleus

  Mainly made of proteins and ribonucleic acid (RNA)

  Produces ribosomes
• Ribosomes

  Made of ribosomal RNA (rRNA) and protein

  Not membrane-bound -- not technically an organelle

  Produces proteins

  Can be found floating around but usually connected to Endoplasmic Reticulum (ER)
• Endoplasmic Reticulum (ER)

  Connected to nucleus in some places

  Network of flattened, interconnected membranes

  Creates a 'tunnel' through substances move

  Two types: Rough ER (RER), Smooth ER (SER)

  RER: process and modify proteins made by ribosomes

  SER: makes lipids (fat)
• Golgi body/apparatus

  Made of flat membrane sacs stacked -- not interconnected

  Processes and packages substances the cell has made

  Membrane pinches off with the substances in it and forms a vesicle which takes the substance where it needs to go
• Lysosomes

  Specific example of a vesicle made by Golgi apparatus

  Membrane-bound sacs that contain digestive enzymes needed to break down other substances -- cellular waste, foreign particles
• Chloroplasts

  Only in plant cells

  Disk shaped

  Have a double membrane, their own DNA and chlorophyll

  Capture light energy (sun) and produce glucose (source of energy) -- photosynthesis

  Can't directly use glucose for energy -- the glucose and oxygen goes to mitochondria for cellular respiration
• Mitochondria

  Have a double membrane (inner membrane highly folded) and their own DNA

  Perform cellular respiration -- combine oxygen and glucose to create ATP (energy source)

  Number of mitochondria depends on how much energy a cell needs -- active cells like muscular cells need more energy

  Cell can't directly use glucose from photosynthesis so mitochondria uses respiration to transform glucose into ATP which can be used
• Cell membrane/plasma membrane

  Separates cell contents from outside environment -- holds organelles together and protects them

  Semi-permeable -- regulates the movement of substances in and out of the cell
• Cell wall

  In plant, fungal, and some prokaryotic cell

  External structure that surrounds the cell membrane

  Gives the cell structural strength and protection
• Cytoplasm

  Watery, gel-like fluid inside the cell membrane

  Gives the cell's shape
• Cytoskeleton

  Network of microtubules, microfilaments and intermediate filaments

  Holds the organelles in place
• Centrioles

  Pair of small, cylindrical structures made of microtubules

  Involved in cell division -- pulling chromosomes apart
• Pili and flagella

  Pili = short

  Flagella = long

  In prokaryotic cells

  Hair-like appendages made of microtubules and enclosed by extension of the cell membrane

  Help the cells move around
• Vacuoles

  Membrane-bound vesicle containing fluid -- water + salt + sugar (in plants, called sap)

  Store substances for when the cell needs it

  Found in most cells, vary in size and quantity -- animal cells contain small and temporary vacuoles, plant cells contain one large permanent vacuole

  In plant cells, more important than storage -- structural support -- turgor pressure