Ch. 4 Cells: The Working Units of Life Originally prepared by Kim B. Foglia. Revised and adapted by Nhan A. Pham
Types of cells
Cell Size
Why organelles? Specialized structures - specialized functions Containers - partition cell into compartments - create different local environments (separate ph s, or concentration of materials) - distinct and incompatible functions Membranes as sites for chemical reactions - unique combinations of lipids and proteins - embedded enzymes and reaction centers
Cells gotta work to live! What jobs do cells have to do? 1. make proteins - proteins control every cell function 2. make energy - for daily life - for growth 3. make more cells - growth - repair - renewal
Cells functions 1. Building proteins - read DNA instructions - build proteins - process proteins (folding, modifying, removing amino acids, adding other molecules ) - address and transport proteins
Building Proteins Organelles involved - nucleus - ribosomes - endoplasmic reticulum (ER) - Golgi apparatus - vesicles nucleus ribosome ER The Protein Assembly Line Golgi apparatus vesicles
Nucleus contains most of cell s DNA How about the rest? Function - protects DNA Structure - nuclear envelope - double membrane - membrane fused in spots to create pores which allow large macromolecules to pass through
1 nuclear membrane DNA production of mrna from DNA in nucleus Nucleus mrna mrna travels from nucleus to ribosome in cytoplasm through nuclear pore 2 nuclear pore mrna small ribosomal subunit large ribosomal subunit cytoplasm
Nucleolus Function ribosome production build ribosome subunits from rrna and proteins exit through nuclear pores to cytoplasm and combine to form functional ribosomes
Ribosomes Function - protein production Structure - rrna and protein large subunit small subunit - 2 subunits combine 0.08µm Ribosomes Rough ER Smooth ER
Types of Ribosomes Free ribosomes - suspended in cytosol - synthesize proteins that function in cytosol Bound ribosomes - attached to endoplasmic reticulum - synthesize proteins for export or for membranes
Endoplasmic Reticulum (ER) little net within the cytoplasm Functions - processes proteins - manufactures membranes - synthesis and hydrolysis of many compounds Structure - membrane connected to nuclear envelope and extends throughout cell
Types of ER rough smooth
Smooth ER functions synthesis - synthesize lipids (oils, phospholipids, steroids and sex hormones) hydrolysis - hydrolyze glycogen into glucose (in liver) - detoxify drugs and poisons (alcohol and barbiturates) by adding OH groups, making them more soluble and easier to flush from the body
Rough ER functions produce proteins for export out of cell - secretory proteins are glycoproteins - packaged into transport vesicles for export produce membrane for the cell - membrane buds off and goes to parts of cell that needs membrane Which cells have lot of rough ER?
Synthesizing proteins cisternal space polypeptide signal sequence mrna ribosome ribosome membrane of endoplasmic reticulum cytoplasm
Golgi Apparatus Structure - consists of flattened sacs (cisternae) with a cis and trans side Function - finishes, sorts, tags and ships cell products - ships products in vesicles secretory vesicles transport vesicles
cis and trans
Vesicle transport protein vesicle budding from rough ER migrating transport vesicle fusion of vesicle with Golgi apparatus ribosome
Making proteins nucleus nuclear pore cell membrane rough ER protein secreted ribosome vesicle proteins smooth ER cytoplasm transport vesicle Golgi apparatus
nucleus DNA endoplasmic reticulum protein on its way! TO: RNA vesicle TO: ribosomes TO: vesicle protein TO: finished protein Making Proteins Regents Biology Golgi apparatus
Secretory Pathway Regents Biology
Lysosomes Structure - vesicles of hydrolytic digestive enzymes, made by rough ER - contain 40 different types of hydrolytic enzymes Function - like stomachs of the cell, digests macromolecules (phagocytosis) - like a clean up crew of the cell, recycles broken cell s parts (autophagy) only in animal cells
1960 1974 white blood cells (macrophages) attack and destroy invaders by digesting them in lysosomes 1974 Nobel prize: Christian de Duve Lysosomes discovery in 1960s
Cellular digestion lyso = breaking things apart some = body Lysosomes fuse with food vacuoles hydrolyze polymers digested into monomers pass to cytosol to become nutrients of cell
Lysosomal enzymes Optimum ph is 5 while ph of cytoplasm is 7. How do lysosomes achieve this acidic environment? Proteins in lysosomal membrane pump H + ions from the cytosol into lysosome. Digestive enzymes are not very active if leaked into cytosol a safety measure for the cell.
When things go bad Defective digestive enzyme in lysosomes pick up biomolecules but can t digest them Over time, fill up with undigested material and grow larger and larger until disrupt cellular function Ex: Tay-Sachs disease build up undigested fat in brain cells Some lysosomal storage diseases Lipids (Gaucher s disease) Glycogen and other polysaccharides (Farber disease, Krabbe disease) Proteins (Schindler s disease)
Sometimes cells need to die Some cells have to die for proper development in an organism Apoptosis (auto-destruct) process Ex: tadpole tail gets reabsorbed when it turns into a frog Ex: loss of webbing between your fingers during fetal development
Syndactyly 6 weeks 15 weeks
Cells gotta work to live! 1. make proteins - proteins control every cell function 2. make energy - for daily life - for growth 3. make more cells - growth - repair - renewal
Making Energy Cells must convert incoming energy to forms that they can use for work - mitochondria: from glucose to ATP - chloroplasts: from sunlight to ATP (active energy) and carbohydrates (stored energy) ATP ATP +
Mitochondria & Chloroplasts Both - convert energy to forms that cells can use - have double membranes - are semi-autonomous organelles (have internal ribosomes, own DNA and enzymes)
Mitochondria Almost all eukaryotic cells have mitochondria There may be 1 very large mitochondrion or 100s to 1000s of individual mitochondria Number of mitochondria is correlated with aerobic metabolic activity more activity à more energy needed à more mitochondria (in nerve and muscle cells)
Mitochondria Structure - double membranes smooth outer membrane and highly folded inner membrane (cristae) - fluid-filled space between 2 membranes - internal fluid-filled space (mitochondrial matrix) with DNA, free ribosomes and enzymes Why 2 membranes? increase surface area for membrane-bound enzymes that synthesize ATP
Chloroplasts belong to a family of plant organelles called plastids 1. Amyloplasts store starch in roots and tubers 2. Chromoplasts pigments in fruits 3. Chloroplasts store chlorophyll and function in photosynthesis
Chloroplasts Structure - double membrane - internal fluid-filled space (stroma), membranous sacs where ATP is made (thylakoids), stacks of thylakoids (grana) - DNA, ribosomes and enzymes - semi-autonomous (move, change shape and reproduce by pinching in two) Function - generate ATP and synthesize sugars via photosynthesis Why 2 membranes? increase surface area for membranebound enzymes that synthesize ATP
1981 - Endosymbiosis Theory Mitochondria and chloroplasts were once free living bacteria engulfed by ancestral eukaryote Endosymbiont cell that lives within another cell (host) in a partnership that is a evolutionary advantage for both. One supplies energy the other Lynn Margulis U of M, Amherst supplies raw materials and protection.
Endosymbiosis Theory Evolution of eukaryotes
Peroxisomes the other digestive enzyme sacs in both animals and plants break down fatty acids into smaller molecules detoxifies alcohol by transferring hydrogen from the poison to oxygen and produce hydrogen peroxide (H 2 O 2 ) which in turns is broken down to water and oxygen by enzymes
Food & Water Storage food vacuoles plant cells central vacuole animal cells contractile vacuole
Vacuoles and Vesicles Function - little transfer ships - food vacuoles (phagocytosis, fuse with lysosomes) - contractile vacuoles (in freshwater protists, pump excess H 2 O out of cell) - central vacuoles (in many mature plant cells)
Vacuoles in plants Functions - storage - stockpiling proteins or inorganic ions - depositing metabolic byproducts - storing pigments - storing defensive compounds against herbivores - selective membrane - control what comes in or goes out
Cells gotta work to live! 1. make proteins - proteins control every cell function 2. make energy - for daily life - for growth 3. make more cells - growth - repair - renewal
Cytoskeleton Function Structural support - maintains shape of cell - provides anchorage for organelles - protein fibers (microfilaments, intermediate filaments, microtubules) motility - cell locomotion (cilia, flagella, etc.) regulation - organizes structures and activities of cell
Cytoskeleton actin microtubule nuclei
Centrioles Cell division - in animal cells, pair of centrioles organize microtubules - spindle fibers guide chromosomes in mitosis