Post on 30-Dec-2015
Cell Structures: Organelles
Cell Structure• Cells vary in SHAPE and SIZE• 5-50 micrometers in diameter; Required flow of
materials in and out of the cell restricts size.• Structures common to all cells:
» Cell Membrane» Genetic material» Cytoplasm
Prokaryotic Cells
• Prokaryotic
• Pro – Before
• Karyote = Nucleus
• No Membrane-bound
organelles
• Less Complex DNA
Eukaryotic Cells
• Eukaryotic• Eu = True• Karyote =
Nucleus
Cell Membrane• Separates cells from their environment• Regulates what enters and leaves the cell.
(SEMI-PERMEABLE)• Aids in protection and support of cell.• Proteins stick out of the surface of the lipid
layer, pass through.
• Carbohydrates attach to Lipids and/or proteins on the surface of the Cell Membrane
• Carbohydrates act as “identifiers”• All cells to recognize and interact with
each other.
Fluid Mosaic Model of
Cell Membrane
Phospholipid Bilayer
Heads: hydrophilic (polar)
Tails: hydrophobic(non-polar)
Protein Channels: help move
materials in/out
[Ex: Antigens on the
cell membrane (proteins) cause
Rejection Syndrome
when tissue not closely matched.]
Structure directs function
Pinocytosis / Form of Endocytosis(Active Transport requires ATP)
• “cell drinking”• Liquid or small
particles are taken into the cell.
• Cell Membrane forms a pouch, pinches off, forming a vacuole, within the cell.
• Once inside the cell, the vacuole opens, releasing its contents.
• Requires Energy*
Phagocytosis / Form of EndocytosisActive Transport requires ATP energy
• Large particles or small Organisms are ingested by the cell.
• Cell Membrane forms a pouch, pinches off, forming a vacuole, within the cell.
• Once inside the cell, the vacuole opens, releasing its contents
• Requires Energy*
Secretions / Form of Exocytosis
Active Transport requires ATP energy
•Mucus (from Goblet epithelial cells)
•Hormones (from endocrine /ductless glands-
secrete directly into the blood &
exocrine glands- secrete via ducts
ex. sweat, digestive juices, tears)
Excretions / Form of ExocytosisActive Transport requires ATP energy
•Wastes
Cell Wall made of cellulose (fibrous material)• Plants, Algae, and
some Bacteria
• Surrounds the Cell Membrane
• Protects and supports cell
• Porous H20, O2 C02 etc. pass through.
• Made of 2 or more layers.
• Lignin ↑ rigidity in woody stems.
• Pectin (gluey) helps hold cells together
Nucleus• Control Center of
the Cell • Round, dense body,
surrounded by a double membrane
• Nuclear membrane – has pores – selective passage of materials in and out of the nucleus.
• Contents of Nucleus remain separate from rest of the cell.
Nucleolus
• Within the Nucleus• Made up of DNA,
RNA, and protein.• Site of Ribosome
production• Chromosomes –
special proteins (DNA) in nucleus of the Cell that contain genetic info passed down to new generation.
Cytoplasm (cytosol)
• Semi fluid substance between the cell membrane and the nucleus.
• Cell (Metabolism) – activities take place in the cytoplasm
• Specialized structures called “organelles” have specific duties to maintain cell homeostasis.
Endoplasmic Reticulum• Transport System • Membrane enclosed, Fluid-filled
channels.
• Components of the cell membrane assembled and proteins modified & exported.
• Smooth ER= no Ribosomes stores enzymes/chemicals involved
in synthesis of membrane lipids & detoxification of drugs (↑ in liver) S&F
• Rough ER= Ribosomes on surface (site of protein synthesis)
Ribosomes (made in nucleolus)
Found in cytoplasm & on rough ER • Smalls particles made
of RNA (ribosomal nucleic acid and protein
• The site of “Protein Synthesis” (↑ in liver) (enzymes are proteins)
S&F
• Proteins (CHON) made from chains of amino acids linked together via peptide bonds Dehydration Synthesis
Functions???
Golgi Bodies • “Packaging Plant” for
proteins – stores protein which can then leave the cell
• Proteins produced by Rough ER are moved to the Golgi Bodies.
•Enzymes in the Golgi Apparatus attach Carbohydrates and lipids to proteins.
• Seceretory Vesicles w/ hormones,
neurotransmitters, etc pinching off from Golgi CM (secretions)
Lysosomes• Suicide Sacs (small sac-
like structures) • Membrane bound organelle
responsible for breaking ↓ proteins, carbohydrates, lipids w/in cell.
• Contains strong digestive/hydrolytic enzymes to digest material no longer useful &food within cell
• Tay Sachs- lacks enzyme to digest specific fat that accumulates in brain cells
• ? Presence in plant cells?
Mitochondria• “Powerhouse” of the
Cell• Cristae – inner
membrane.• Releases energy from
food molecules to be used by the cell.
Muscle Cells have more mitochondria – because they require more energy.
• Site of Cell Respiration:
food energy to ATP
enzymes
6O2 + C6H12O6 -----> 6CO2 + 6H20 + ATP
•All of our Mitochondria come from the Ovum, or egg Cell (maternal)
•Mitochondrion each have their own DNA and are capable of duplicating themselves*
Vacuoles
• “Storage Containers”• materials food,
water, sugar, starches, salts, minerals, waste products
• Larger in Plants- filled with cell sap- occupies most of the interior of the plant cell
Smaller in AnimalsSome animals have contractile vacuoles to digest food.
Cytoskeleton • Network of protein
filaments that help maintain cell shape and aid in movement
Microfilaments: threadlike made of
protein actin flexible framework aid in
movement of cytoplasm
cyclosis/cytoplasmic streaming
Microtubules: tubelike made of tubulin proteins
centrioles, flagella, cilia
Centrioles (found in area of centrosome)
• Found in Animal Cells only (plants have microtubules in centrosome)
• Made from microtubules, found in pairs near the nucleus
• Involved in movement of Chromosomes during Cell Division
• Similar structures found in Cilia and Flagella
Cilia• Microtubules support
hair-like projections from the cell surface known as Cilia.
• Cilia aid in the movement of substances along the cell’s surface – as in the mucus lining your nasal passage.
Cilia
• Protozoa – a unicellular, eukaryotic organism belonging to the Kingdom Protista
• Cilia are short, thread-like structures that help unicellular organisms move.
Flagella
Plastids
•Internal membranes Store food & pigments in plants
•Chloroplasts- store chlorophyll pigments in green plants, site of photosynthesis
•Leucoplasts- store starch granules
•Chromoplasts- store other pigment molecules
Chloroplasts
• Double-Membrane• Have their own DNA
like Mitochondria, believed to have originated as a captured bacterium.*
• Use the energy from sunlight to make energy-rich food molecules in a process of Photosynthesis
chlorophyll/light
6CO2 + 6H20 C6H12O6 + 6O2
Compare and Contrast Mitochondria and Chloroplasts
Power Stations *change energy from 1 form to another
*2x membrane structures
*contain their own DNA
(precursor eukaryotes (endosymbiotic theory)
Mitochondria: convert chemical energy stored in food to ATP through C.R.
Chloroplast: trap light energy & convert it to chemical energy through photosynthesis
Peroxisome
• Vesicles that contain enzymes (catalase/hydrogen peroxidase) that help protect the cell vs H2O2 hydrogen peroxide built up from cell metabolism.
hydrogen peroxidase / catalase
• 2H2O2 2H20 + O2