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Cell Structure and Function
General
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Size in order of micrometer (around 100 in humans)
Cell is basic unit of life: reproduce and grow, respond to stimuli, use material from environment,
adapt, stay homeostatic…
All living beings are made of cells
Cells only come from previous cells
As cell size increase, surface area increase, material exchange increase
As cell size decrease, ratio of surface area to volume increases
^creates a limit to how big cell can be before it divides
Resolution of microscope is ability to distinguish between 2 adjacent points
Come microscopes can view alive cells such as light micrograph
Cells should be treated before such as dyed to show difference in color, treated with electrondense metals (gold), sliced in a matrix to show inside

Cell Organization & Evolution
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Prokaryotes (no nucleus, has DNA but surrounded by membrane, first to evolve)
o Eubacteria
o Archaebacterial: origin of eukaryotes, live in harsh conditions (like early earth), found in
hostile areas
Eukaryotes
o Protists (single celled organisms)
o Animal, plant, fungi cells
Both have plasma membrane which is outer later that control what enters and exits the cell
(selectively permeable, sometimes due to proteins scattered on surface); is phospholipid bilayer
Both contain cytoplasm: semifluid (due to protein presence) made of water and other molecules
suspended of dissolved
Nucleus
o Membrane enclosed
o Contains DNA
o Could have formed by invagination of plasma membrane: pocket formed around DNA
Mitochondria
o Formed by endosymbiosis: cell eats up other cell (similar process for chloroplast)

Plasma Membrane
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Small, lipid soluble molecules such as oxygen and carbon dioxide can cross membrane easily
Water can cross through protein channels called aquaporins
Diffusion: passive (doesn’t need energy to happen), molecules go from high concentration to
lower concentration, happens in both directions but one more than other until equilibrium
(then same rate) ex
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Tonicity is osmotic characteristics of solution across membrane
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Intravenous solutions are isotonic
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Ex
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Used by WBC to kill pathogens (phagocytosis)
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Using special membrane protein, receptor, to concentrate molecules of
interest to endocytosis (receptor-mediated endocytosis)
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Nucleus
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In eukaryotic cells
Stores genetic information
Each type of cell has genes on and genes off, but they are all present
DNA, RNA (as intermediary) helps in the specification of protein in cell which determines cell
function
Chromatin is combination of DNA and proteins that make up chromosomes
Chromatin can be tightly coiled during cell division so that chromosomes are visible
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chain of sugar => glycoproteins and glycolipids; vesicles move molecules to other parts of cell
namely plasma membrane; involved in processing, packaging and secretion
Lysosomes: membranous sacs by GA; contain hydrolytic enzymes; found in all cells but mostly
WBC (when joined with endocytic vesicle containing microbe, it digests its content using by
lysosomal enzymes); cause auto digestion when cell parts are broken down by own lysosomes;
disease such as Ty-Sachs where lysosomal enzymes are missing to things don’t get digested in
nerve cells

Cytoskeleton
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Crisscross of protein fibers in cytoplasm
Makes cell shape
Move or fix organelles
Microtubules:
o Bigger than actin filaments
o Cylinder than contains rows of proteins called tubulin
o Assembled around centrosome (organizing center)
o Form spindle fiber during cell division; assist movement of chromosomes
Actin filaments
o Protein called actin
o Long, very thin fibers occurring in bundles
o Involved in movement
o Found in microvilli which extend from cell, lengthen and shorten
Intermediate filaments: size between both; different structure and function depending on cell
Cilia and flagella: involved in movement; ex
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2
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4
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Its reactants are called substrates after
which they are named, ex
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Have specific regions called active sites
where substrates are brought together to react
Coenzymes are no protein molecules that help enzymes and sometimes contribute atoms;
include vitamins; ex
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NADH gives H and electrons to pyruvate and makes it lactase
and recycles into NAD+
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Only
produces 2 ATP per glucose



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