Are the building blocks of organisms.

(Av.size: 20 micrometers)

Small due to:

• Cell membrane considerations
• Nucleus to cytoplasm ratio
• Supply to demand ratio

Electron microscope

Uses a beam of electrons.

• Are membrane bound structures.
• Have specialised functions to perform.
• Some do not have a membrane surrounding them.
• chloroplast & permanent vacuoles are only found in plant cells.

• Controls all cell activities
• Contains genes
• Contains code for protein synthesis
• Involved in production of Ribosome’s & RNA (essential for cell division)

• Contains- nucleic acids (DNA&RNA)
• Double membrane = Nuclear envelope
• Encrusted with ribosome’s
• Covered in pores
• Continuous with RER

• Protein isolation & transport

• Consists of interconnecting flattened tubules (cisternae) stacked together.
• Membrane is encrusted with ribosome’s (Polysome configuration).

• Steroid synthesis
• Lipid synthesis
• Lipid & steroid transportation
• Storage of Ca ions

• No ribosomes
• Rarely form cisternae
• Membrane distinctly more tubular & smooth

• Increases in surface area for chemical reactions
• Provides a pathway for transporting materials through the cell
• Collects & stores materials made by the cell.

• 70s prokaryotes (+ chloroplasts and mitochondria)
• 80s eukaryotes

Consists of small & large subunit.

• A stack of flattened cavities
• Forms lysosomes
• Produces enzymes for secretion
• Protein and carbohydrate combine to form glycoprotein

Vesicles

Contain proteins for:

• Secretion
• To become part of plasma membrane
• To become functions of enzymes

• Contain digestive hydrolytic enzyme
• Fuse with the target, enzymes breakdown the target, products are absorbed by the cell
• Secretes their enzymes outside the cell to breakdown other cells
• Digests stuff taken in from the environment by the cell
• Digests parts of cells e.g.: worn out organelles (autolysis)

• Synthesis of ATP
• Biosynthesis
• Found in all eukaryotes except mature red blood cells.
• Number depends on activity of cell.
• High metabolically active ones- have large numbers.
• Low ones- have small numbers.

70s ribosome’s, DNA circlet, Matrix- fluid of mitochondria, double membrane & Cristae which is an inner folded membrane containing stalked particles.

• Site of photosynthesis

• Lamellae, DNA circlet, double membrane, Stroma- fluid of chloroplast, starch grains, granum, thylakoid & chlorophyll.

• Contains cellulose & hemi cellulose.
• Are fully permeable & strong.

• X- weave made from interwoven fibres.
• Consists of straight chains of beta-glucose, forms micro fibrils & macro fibrils

• Forms the spindle during cell division

• 2 cylinders of protein microtubules arranged at 90 degrees
• Not membrane bound

Bacterial cells also contain flagellum, plasmid and capsule.

• Cells form specialised cells, which form tissues.
• Tissues- are cells of one type, which carry out one function. E.g.: muscle, nerves
• Organ- is a structure made up of different tissues performing certain tasks.

• Microvilli increase surface area for absorption.
• Mitochondria synthesises ATP for active transport

• Elongated to absorb light
• Contains many chloroplasts for photosynthesis

Used to obtain a sample of isolated organelles.

• Homogenise sample of cells
  • Conditions
  • Ice cold- to stop biological processes
  • Isotonic solution- to prevent osmotic damage
• Add solution to a centrifuge & spin at a low speed
  • Densest organelles spin down first. E.g.: nucleus
• Place supernatant back into centrifuge & spin at a higher speed
  • Next organelle spins down e.g.: mitochondria
• Repeat & spin & higher speed
  • e.g.: RER, SER, GA.

• Consists of 40% lipids & 60% protein.

• The polar nature of phospholipids explains membrane assembly. 

• Phospholipid heads are hydrophilic.

• Fatty acid tails are hydrophobic.

• Fluid- phospholipids move around the medium.

• Mosaic- phospholipids are not attached to each other/arranged in sequence.

Movement in + out of cells

1. Diffusion (passive)

• Small, gas mols pass between phospholipid mols in membrane. (H-L)

• Water is a special case (osmosis)

2. Facilitated diffusion (passive)

• Movement of lipid soluble, small & gas mols from a (H-L) conc. through intrinsic membrane proteins

• Fatty acid tails creates a hydrophobic barrier to entry.

• 2 types of f-d proteins

• Pore (channel) proteins

• Can be gated by chemicals / a change in voltage is required to open the protein pore.

• Carrier proteins

• Mols. undergo a conformational shape change.

• Small mols. that cannot pass through the phospholipid bilayer, glucose, charged mols., ions. Na, K move by facilitated diffusion.

• Movement of water mols from a less to more (-) WP via a selectively permeable.

• Pure (distilled) water has the highest WP = 0 & has a greater average KE of water mols.

• Water + solute has a (-) WP & has a less average KE of water mols.

• WP is the ability of water mols to move. (Kpa)

• WP = OP + PP 

• Cell WP = cytoplasm’s OP + wall PP

• When plant fully turgid WP=0

• Uses KE of mols., or ions, themselves as the motive power to move these materials… so direction of movement depends upon concentration & / electrical (charge) gradients.

• E.g.: diffusion, osmosis, facilitated diffusion

4. Active transport (active)

• Uses energy from ATP to move molecules / ions against unfavourable concentration & / electrical gradients. (L-H)

• Movement is against conc. gradient

• Requires the hydrolysis of ATP

• E.g.: Na, K pumping by nerve cell membranes.

1. Endocytosis

• Into cells (active process)

• Plasma membrane forms a vesicle around substance & vesicles taken into cell.

• Phagocytosis = cells + solid particles e.g.: macrophages

• Pinocytosis = cells + dissolved molecules

2. Exocytosis

• Out of cell (active process)

• Materials formed by the cell are packaged in secretary vesicles, which fuse with the plasma membrane to release their contents.

• E.g.: secreted proteins (digestive enzymes & hormones)