Download Science - B1 Cell Structure and Transport in and out of Cells

Cells
Structure, microscopy, membranes
Click for excellent resource…
http://sciencelearn.org.nz/Contexts/Exploring‐with‐
Microscopes/Sci‐Media/Interactives/Which‐microscope
Microscopy – which microscope?
What do you want to see?
• Dead or alive?
• Surface or cross section?
• Build up a 3D model?
• Resolution?
• Avoid removing moisture?
Staining
• Allows transparent structures to be seen
• Differential Staining in Light Microscopes
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Different stains taken up by different parts of the cells
Eosin (pink) stains cytoplasm
Methylene blue (blue!) stains DNA
Creates contrast • Staining in Electron Microscopes
• Heavy metals (lead) create more scattering making structures appear darker
Eye Piece Graticules and Stage Micrometers
Cell structure as seen through a light microscope
Onion Cell Mitosis
x160
Magnification and Resolution
Calculations
How I remember it … Image size = object size x magnification
Calculating magnification
1. Write down want you’ve got 2. Convert into the same unit
3. Plug the numbers into the equation
4. Calculate
Microscope Drawing
Cell Ultrastructure/Organ
elles
Learn the functions of all of them! Pages 11‐13 in the revision guide.
Photomicrographs
• Make sure you know what the real thing looks like
• Just ‘google’ the name of the organelle followed by the word photomicrograph
The interrelationship between organelles involved in the production and secretion of proteins
Protein synthesis occurs at ribosomes Free ribosomes produce intracellular proteins that stay in the cytoplasm
Ribosomes on the rough endoplasmic reticulum (RER) produce proteins that are secreted (NOT excreted as it says in RG) or attached to the cell membrane E.g. Hormones secreted or receptor on membrane
Proteins produced at the RER are folded and processed in the RER. They are then transported in vesicles to the golgi apparatus where further processing occurs. E.g. adding sugar chains to immunoglobulins. They are then transported to the plasma membrane in vesicles and released by exocytosis
Cytoskeleton
• Structure
• Network of proteins threads
• Microfilaments and microtubules
• Function
• Support organelles and keep • Strengthen and maintain cell shape
• Movement of materials
• Chromosomes in mitosis
• Cell movement
• Cilia
• flagella
Prokaryotes vs. Eukaryotes
Cell Membranes – Fluid Mosaic Model
Role of cell membranes
• Selectively/partially permeable barrier (NOT semi)
• Between cell and environments (plasma membrane)
• Between organelle and cytoplasm (e.g. out mitochondrial membrane)
• Within organelles (e.g. inner mitochondrial membrane)
• Site of chemical reactions
• E.g. stages in photosynthesis and respiration
• Site of cell communication (cell signalling)
• Receptors for •
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Hormones
Neurotransmitters
Cytokines
Antigens (T‐cells)
Function of Components
• Phospholipid bilayer • Hydrophilic heads are polar and interact with medium whilst hydrophobic tails form a nonpolar barrier • Barrier for ions and soluble molecules (but water itself is small enough to pass through)
• Soluble to non‐polar lipids, cholesterol based steroid hormones, fat‐soluble vitamins
• Cholesterol
• Fits between phospholipids
• Binds to tails causing tighter packing
• Reduces fluidity
• Proteins
• Control movement across membrane
• Channel proteins
• Facilitated diffusion
• Active transport
• Receptors for cell signalling triggering a chemical reaction
• Glycoproteins and Glycolipids
• Binding sites for drugs, hormones and antibodies
• Receptors for cell‐signalling
• Antigens
Transport across membranes ‐ diffusion
Transport across membranes ‐ osmosis
Transport across membranes ‐ osmosis
Transport across membranes
• Channel proteins
• Facilitated Diffusion
• Facilitated Diffusion – co‐transporter
• Facilitated Diffusion – antiport
• Active Transport – Na+K+ATPase
Exocytosis
Endocytosis
Investigating membrane permeability ‐ Temperature
• Measure the leakage of coloured pigment from beetroot
• Higher leakage = higher permeability
• 5 equal size pieces
• Rinse
• Range of temperatures 10, 10 etc.
• Leave for equal time • Remove beetroot and se colorimeter to measure absorbance
• Higher the absorbance, the higher the permeability
Investigating membrane permeability ‐ Temperature
Investigating membrane permeability ‐ Temperature
Investigating Diffusion ‐ Factors
• Concentration gradient • Diffusion distance
• Surface area
• Temperature (KE)
Investigating Diffusion ‐ Factors
Investigating Diffusion ‐ Factors