a tour of the cell ap biology fall 2015. cells are necessarily small most cells are between 1 and...
TRANSCRIPT
A Tour of the Cell
AP Biology
Fall 2015
Cells are necessarily small
• Most cells are between 1 and 100 micrometers
• They have to be that small to allow for intracellular communication and transport.
• cell size animation
•
• If a cell is too big, the surface area to volume ratio is too low. The surface area is too small compared to the volume and the cell cannot take in enough to “feed” the center portion.
Prokaryotic Cells vs. Eukaryotic Cells: What unites us
• All cells have a plasma membrane (lipid bilayer) that surrounds the cell
• All cells have a cytosol which is a thick chemical soup (mostly water) in which everything inside of a cell floats.
• All cells have chromosomes (DNA)• All cells have ribosomes (structures that carry out the
process of producing proteins)
Prokaryotic Cells vs. Eukaryotic Cells: What separates us
• Prokaryotes have no membrane around the cell’s DNA. Eukaryotes have a nucleus that holds the DNA and the nucleus is surrounded with a nuclear membrane
Prokaryotic Cells vs. Eukaryotic Cells: What separates us
• Prokaryotes have no other membrane-bound organelles. Eukaryotes have many membrane bound organelles suspended in the cytoplasm.
• Prokaryotes are generally smaller. Eukaryotes are generally larger.
• Prokaryotes are only bacteria. Eukaryotes are never bacteria but comprise the other kingdoms
Prokaryotic Cells vs. Eukaryotic Cells: What separates us
To sum up:
1. Prokaryotes are small and simple, lacking nuclear membranes as well as other membrane-bound organelles.
2. Eukaryotes are large and complex with a nuclear membrane and many other membrane-bound organelles
The Nucleus
• Function of the nucleus: contains most of the genes. – Nuclear envelope– Nuclear pores (holes in
the nuclear envelope)– Chromosomes (DNA)– Nucleolus-makes RNA
including ribosomes
Ribosomes
• Function – ribosomes carry out protein synthesis– Free ribosomes– Bound ribosomes
Endomembrane system
•
Consists of many membrane organelles that are either in direct contact with each other or transfer vesicles to each other.• Nuclear envelope• Endoplasmic reticulum• Golgi apparatus• Lysosomes• Vacuoles• plasma membrane
Endoplasmic Reticulum (ER)
• 1. Rough– The ribosomes function to
produce secretory proteins. (Also called glycoproteins)
– Makes membranes
2. Smooth– Synthesis of lipids (steroids)– Metabolism of carbohydrates– detoxification of drugs and
poisons (in liver cells)
Golgi ApparatusHas 2 “faces”cis face – receives vesicle from ERtrans face – produces vesiclesmodification occurs between cis and trans faces. Vesicle also gets tagged destination.
•
Lysosomes
•
Membrane-bound sac that the cell uses to digest macromolecules.
Contains enzymes that can digest all major classes of macromolecules. These enzymes operate best at a low pH. The lysosome maintains that pH by constantly pumping H ions in.
Phagocytosis – amoebas, white blood cells
Autophagy – recycles cellular components. Ex: liver cells
Programmed destruction – tadpoles, insect metamorphosis
Vacuoles
• Diverse Functions:– Food vacuole– Contractile vacuole– Central vacuole (tonoplast =
membrane)
Central vacuoles can hold:
poisons, toxins, irritants, pigment, proteins, inorganic ions, water
Mitochondria
•
Transforms energy in glucose to ATP in a process called cellular respiration.
Mitochondria have their own ribosomes and their own DNA
Called semiautonomous
Plastids
• Amyloplasts
Chromoplasts
Chloroplasts
Chloroplasts
•
Like mitochondria, chloroplasts have their own ribosomes and DNA and are also semiautonomous
Chloroplasts are found only in plants and some protists – they convert solar energy sunlight into chemical energy and drive the synthesis of organic compounds.
Peroxisomes
Compartments that contain enzymes that transfer hydrogen to oxygen
Produce hydrogen peroxide as a by-product.
Other enzymes (catalase, for example) break the hydrogen peroxide down.
Transferring hydrogen work in breaking down fatty acids and detoxifying alcohol.
Plants vs. Animals
Plant cells do not have:
Lysosomes
Centrioles
Flagella (except some plant sperm)
Animal cells do not have:
Chloroplasts
Central vacuole
Tonoplast
Cell wall
plasmodesmata
Cytoskeleton• A network of fibers in
the cytoplasm.• It’s major functions are:
– organization– Mechanical support– Maintains shape – Anchorage for organelles
• The cytoskeleton is dynamic
Cell Surfaces and Junctions Plant Cells
cell wall – protects the cell– maintains the shape of the cell– prevents excessive uptake of water
What are cell walls made of??
Intercellular communication and connection
Plants – Plasmodesmata – cell to cell communication in plants
Animals – Tight junctions and
demsosmes: fasten cells together
Gap Junctions – provide cytoplasmic channels between adjacent cells (function just like plasmodesmata)