organelles
DESCRIPTION
Organelles. Types of Organelles. Nonmembranous organelles: no membrane direct contact with cytosol (cytoplasm) Membranous organelles: covered with plasma membrane isolated from cytosol (cytoplasm). 6 types of nonmembranous organelles: cytoskeleton microvilli centrioles. - PowerPoint PPT PresentationTRANSCRIPT
Organelles
Types of Organelles
• Nonmembranous organelles: – no membrane– direct contact with cytosol (cytoplasm)
• Membranous organelles: – covered with plasma membrane– isolated from cytosol (cytoplasm)• 6 types of nonmembranous organelles: – cytoskeleton – microvilli – centrioles
-cilia – ribosomes – proteasomes
How does the nucleus control the cell?• Is the cell’s control center• Nucleus:
– largest organelle• Nuclear envelope:
– double membrane around the nucleus
• Perinuclear space:– between 2 layers of
nuclear envelope • Nuclear pores:
– communication passages
Within the Nucleus• DNA:– all information to build and run organisms
• Nucleoplasm:– fluid containing ions, enzymes, nucleotides, and
some RNA
• Nuclear matrix:– support filaments
Nucleoli in Nucleus• Are related to protein production• Are made of RNA, enzymes, and histones• Synthesize rRNA and ribosomal subunits
Ribosomes
SEM of rough ER (ribosomes attached to
membranes)
Ribosomes• Two types:
– free ribosomes in cytoplasm:• proteins for cell
– fixed ribosomes attached to ER:• proteins for secretion
• Translate the genetic code into proteins.• Build polypeptides in protein synthesis• 60% RNA and 40% protein.
Proteasomes (found in the nucleus and the cytoplasm)
• Contain enzymes (proteases)• Disassemble damaged proteins for recycling
Endoplasmic reticulum
TEM of rough ER (ribosomes attached to
membranes)
Endoplasmic Reticulum (ER)• endo = within, plasm = cytoplasm, reticulum = network
• Little net• Network of interconnected closed membrane vesicles• Single membrane• Divides cell into compartments• Place of protein and phospholipids synthesis• Connected with the nuclear envelope• Cisternae are storage chambers within membranes
Functions of ER
• Synthesis of proteins, carbohydrates, and lipids• Storage of synthesized molecules and materials• Transport of materials within the ER• Detoxification of drugs or toxins
• It is of 2 types:1. Rough ER2. Smooth ER
Rough Endoplasmic Reticulum• Network of continuous sacs,
studded with ribosomes.• Manufactures, pro-cesses, and
transports proteins for export from cell.
• Continuous with nuclear envelope.
• Surface covered with ribosomes:– active in protein and
glycoprotein synthesis (late r inserted in the cell membrane and secreted from the cell)
– folds polypeptides protein structures
– encloses products in transport vesicles
Smooth Endoplasmic Reticulum
• Similar in appearance to rough ER, but without the ribosomes.
• Involved in the production of lipids, carbohydrate metabolism, and detoxification of drugs and poisons.
• Ca (2+) storage• Synthesizes lipids and carbohydrates:– phospholipids and cholesterol (membranes)– steroid hormones (reproductive system)– glycerides (storage in liver and fat cells)– glycogen (storage in muscles)
Golgi complex
TEM of Golgi complex
ER and Golgi complex
The ER and Golgi complex work together to secrete substances from the cell (via exocytosis)
Golgi Bodies
– Contains several hundred flattened compartments and vesicles
– Secretory vesicles:• modify and package products for exocytosis
– Membrane renewal vesicles:• add or remove membrane components
– Transport vesicles:• Carry materials to and from Golgi apparatus
Golgi Bodies
Lysosomes
SEM of two lysosomes containing undigested
materialCell death caused by lysosomes
removes webbing
Lysosome Functions• Powerful enzyme-containing vesicles:
– lyso = dissolve, soma = body• Clean up inside cells:
– break down large molecules– attack bacteria– recycle damaged organelles– ejects wastes by exocytosis
• Primary lysosome: – formed by Golgi and inactive enzymes
• Secondary lysosome: – lysosome fused with damaged organelle– digestive enzymes activated– toxic chemicals isolated
ChloroplastsTEM of
chloroplasts
• Photosynthetic plant cells also contain chloroplasts (a plastid) that capture energy from sunlight.
• They produce and store carbohydrates like miniature gardens and warehouses.
• LOCATIONinside photosynthetic cells only, suspended in the cytosol
• DESCRIPTION green, disk shaped contains chlorophyll and the enzymes required for photosynthesis
FUNCTION• absorb sunlight energy • photosynthesis occurs here: glucose is synthesized from Carbon Dioxide and
water
Chloroplasts
Chloroplast
PRESENT IN:• PROKARYOTIC CELLS? NO• PLANT CELLS? YES• ANIMAL CELLS?
NO
VISIBLE WITH:• LIGHT MICROCOPE?
YES
• ELECTRON MICROSCOPE?YES
Mitochondria
TEM SEM
Notice the many folds
MitochondriaTubular susage shapedDouble membraneOwn DNA and ribosomesHave smooth outer membrane and folded inner membrane
(cristae)Matrix:
– fluid around cristae
Mitochondrial Function• Mitochondrion takes chemical energy from food
(glucose):– produces energy molecule ATP
Figure 3–9b
Animal and plant cells
Animal cell Plant cell
Cell skeleton
Three structures that make up the cytoskeleton of a cell
The Cytoskeleton(Structural proteins for shape and strength)
• Microfilaments• Solid rods of globular proteins.• Important component of cytoskeleton which
offers support to cell structure.Thin filaments composed of the protein actin:
• provide additional mechanical strength • durable (collagen)• strengthen cell and maintain shape• stabilize organelles• stabilize cell position
• Microtubules – Large, hollow tubes of
tubulin protein:• attach to centrosome• strengthen cell and
anchor organelles• change cell shape• form spindle
apparatus
• Microvilli• Increase surface area for
absorption• Attach to cytoskeleton