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Robert Hooke (1600s)
- “the father of microscopy”
- it was Hooke who coined the term “cell” to describe the basic unit of life
- He invented the microscope
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Mattais Schleiden and Theodore Schwann (1830s)
all living things are composed of one or more cells
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In the addition to morphology, cells differ in:
- Their ability to move
- Their internal organization (prokaryotic versus eukaryotic)
- Their metabolic activities
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Are the following organic molecules alive? Proteins, carbohydrates, lipids, and nucleic acids
NO
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Cell Theory
- All organisms are composed of cells and cell products
- All cells come from previously existing cells
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Are all of the cells within an organism the same?
NO
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How many distinct cell types make up the human body?
210 distinct cell types
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Ectoderm
- Central nervous system
- Retina and lens
- Cranial and sensory
- Ganglia and nerves
- Pigment cells
- Head connective tissue
- Epidermis
- Hair
- Mammary glands
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Mesoderm
- Skull
- Head, skeletal muscle
- Skeleton
- Dermis of skin
- Connective tissue
- Urogenital system
- Heart
- Blood, lymph cells
- Spleen
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Endoderm
- Stomach
- Colon
- Liver
- Pancreas
- Urinary bladder
- Epithelial parts of
- trachea
- lungs
- pharynx
- thyroid
- intestine
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All living cells on Earth fall into two categories
- Prokaryotic cells
- Eukaryotic cells
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What is the difference between the two?
One has a nucleus and one does not
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Prokaryotic cells
- only domains: Bacteria and Archaea
- does not have nucleus
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Eukaryotic cells
- Plant and Animal Kingdoms, including the Fungi (multicellular molds and unicellular yeast)
- has nucleus
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What type of cells do humans have?
Eukaryotic cells
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Prokaryotic cells are ___ compared to eukaryotic cells and eukaryotic cells are ___ compared to prokaryotic cells
- tiny
- large
- Eukaryotic cells are much more complex which is why they are larger
-
Prokaryotic cells consist of...
a single enclosed compartment that is surrounded by plasma membrane, lacks a defined nucleus, and has a relatively simple organization; DNA is located in a nucleoid region.
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Eukaryotic cells contain a...
- defined membrane-bound nucleus that is absent in prokaryotes. The nucleus segregates the cellular DNA from the rest of the cell.
- Eukaryotic organisms can be either unicellular or multicellular
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There are three main parts of a cell
- 1) the plasma membrane
- 2) the cytoplasm
- 3) the nucleus
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Plasma Membrane (Plasmalemma):
- Defines the extent of the cell (separates the living cell from its nonliving surroundings
- The thin/flexible layer that separates the intracellular (inside) and extracellular (outside) compartments
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Phospholipids are composed of the following:
- 2 fatty acids chains (tail= non-polar or hydrophobic= H2O- fearing)
- A phosphate group (head= polar or hydrophilic= H2O- loving)
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Proteins make up __% of the membrane mass
50%
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Membrane phospholipids and proteins can ___ about in the plane of the membrane
drift
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This behavior leads to the description of a membrane as a...
fluid mosaic
-
“Fluid”
Molecules can move freely within the membrane
-
“Mosaic”
A diversity of proteins exist within the membrane
-
Integral Membrane Proteins
- transmembrane
- span entire width of membrane and contain both hydrophilic and hydrophobic
- regions
-
Peripheral Membrane Proteins
- do not span the entire membrane
- are loosely associated with other proteins or lipid molecules
- Glycolipids (~10%)
- cholesterol (~5-20%)
- carbohydrates
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Membranes of the cell provides... and some plasma membranes act as...
- barrier against substances outside the cell
- receptors for cellular communication
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Membranes are selectively permeable which means...
- They allow some substances to cross more easily than others (i.e. size or
- charge)
- They block passage of some substances altogether
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Diffusion is one result of...
the movement of particles (High [] → Low [])
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Molecules tend to spread into...
the available space
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Diffusion is _____ transport which means __ ______ is needed
-
The solution has two different parts to a solution
- Solute= what gets dissolved
- Solvent= what does the dissolving
- Ex. Kool-Aid is the solute and water is the solvent
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“Concentrated solution”
higher solute and lower solvent
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“Diluted solution”
lower solute and higher solvent
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Another type of passive transport is ______ ________, the transport of some substances by specific transport proteins that act as selective corridors
- facilitated diffusion
- The traffic of some substances can only occur through transport proteins
- Glucose, for example, requires a transport protein to move into the cell
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Osmosis is...
- the passive transport of water across a selectively permeable membrane:
- High [H2O] → Low [H2O]
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The survival of a cell depends on...
its ability to balance water uptake and loss
-
Isotonic Solution
“stay the same”
-
Hypertonic Solution
“shrink”
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Hypotonic Solution
“swell”
-
Osmoregulation is...
the control of water balance in animals
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Endocytosis
mechanism by which particles enter cells
-
3 forms of endocytosis:
- Phagocytosis- cellular eating
- Pinocytosis- cellular drinking
- Receptor-mediated endocytosis- more specific kind of binding involving receptors that are embedded within the plasma membrane
-
Phagocytosis (“cellular eating”)
a cell engulfs a particle and packages it within a food vacuole (ex. Most WBCs)
-
Pinocytosis (“cellular drinking”) is primarily used for...
- the absorption of extracellular fluids (ECF)
- In contrast to phagocytosis, generates very small vesicles
- Unspecific in the substances that it transports
-
Receptor-mediated endocytosis is triggered by...
- the binding of external molecules to membrane proteins
- Upon membrane proteins binding to certain molecules, the membrane invaginates and forms a coat pit which then pinch off to become a coated vesicle (ex. Low Density Lipoproteins or viruses)
-
Exocytosis
- mechanism that moves substances (enclosed in a vesicle) out of the cell migrates to the plasma membrane proteins from the vesicles (v-SNAREs) bind with membrane proteins (t-SNAREs)
- lipid layers from both membranes fuse, and the vesicle releases its contents to the outside of the cell
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