1. Chapter 5: Membranes Main topics --- Membrane structure.
Cell adhesion and junctions – Not in lecture but STUDY pp
Membrane transport

4. Membranes are selectively
Membranes are selectively* permeable – some substances can pass through and other cannot. (*= differentially permeable, semipermeable)

5. Passive transport across membranes
Simple diffusion – movement of solutes from high concentration to low
Osmosis – movement of solvent (water). Like diffusion, water moves from where it is most abundant to where it is least abundant.
it moves from the dilute side to the concentrated one
i.e. from the hypotonic side to the hypertonic side
Facilitated diffusion – movement through channel proteins and carrier proteins.

7. Active transport
Energy is used to pump substances in a direction opposite to that in which they would normally diffuse.
Primary – ATP provides energy to pump cations (+) across the membrane
Secondary – Re-diffusion of pumped cations drives pumps for other molecules.

10. Cell Structure and Function
- emphasizing eukaryotic cells

11. Cell size

12. Prokaryotic Cells Bacteria and Archaea Small (1 µm diameter)
Surrounded by plasma membrane
(May be walls or other structures outside it.)
Contain ribosomes, nucleoid region (DNA)
No distinct, membrane-bound organelles
(May be internal membrane systems)

14. Eukaryotic cells Protists, Fungi, Plants, and Animals
Larger ( µm) and more complex cells
Surrounded by plasma membrane (p.m.)
Plant cells have a cellulose wall outside p.m.
Internal cytoskeleton
Elaborate endomembrane system
Distinctive membrane-bound organelles

16. Cellular Organelles Ribosomes Nucleus
Endoplasmic reticulum (ER) and Golgi
Vacuoles and lysosomes
Mitochondria
Chloroplasts and other plastids

17. Ribosomes Found in both prokaryotes and eukaryotes
NOT surrounded by a membrane
Made of RNA and protein
Some are free, some attached to ER
Site where amino acids are assembled into polypeptides.
Most cells contain thousands of them.

18. Nucleus Nuclear envelope is made of two membranes
(two phospholipid bilayers)
Large pores connect nucleoplasm to cytoplasm.
Large dark area called nucleolus
Where ribosomal RNA is made
DNA can be in various forms
Tightly wound-up into distinct chromosomes
Loosely distributed as formless chromatin

20. Endomembrane System The chemical factory of the cell
Rough endoplasmic reticulum covered in ribosomes, for protein synthesis.
Smooth endoplasmic reticulum for lipid synthesis and modification of proteins
Golgi apparatus for further modification and packaging for secretion.
Membranes are very fluid and dynamic.

22. Vacuoles and lysosomes
Various membrane-bound compartments
May be considered part of endomembrane system
Lysosomes contain digestive enzymes
Most plant cells contain a very large central vacuole.

23. Mitochondrion (plural = mitochondria)
Where sugars are broken down to yield energy.
All eukaryotes have them (plants too!!!).
Smooth outer membrane.
Separate inner membrane deeply in-folded
Folds are called cristae
Innner membrane creates two compartments:
Inner “matrix”
Inter-membrane space btw. inner & outer membranes

25. Plastids
Chloroplasts in plant cells are where photosynthesis occurs and sugars are made.
Like mitochondria, they have inner and outer membranes.
Will discuss internal structure later.
Other plastids in plants include -
chromoplasts: pigments other than chlorophyll
leucoplasts: colorless, contain starch

27. Cytoskeleton
Protein fibers involved in support and movement of cellular structures.
Microfilaments (actin)
Intermediate filaments (keratin-like proteins)
Microtubules (tubulin)
Among other roles, microtubules support and create movement in cilia and flagella.