Chapter 6 A Tour of the Cell The cell is the basic unit of life Although cells differ substantially from one another, they all share certain characteristics that reflect a common ancestry and remind us of the unifying theme of evolution Three main parts of a cell Plasma membrane Cytoplasm Genetic control 1
History of the cell First microscopes 1590 - technology The term cell was first coined by Robert Hooke in 1665. Little knowledge was gained about cell structure function until the 1950 s WHY??? Technology Microscopes Essential tool for studying the cell Light microscopes Ratio of image size to actual size magnification Measure of clarity resolution Many of the essential components of cells were too small for adequate resolution by a light microscope Electron microscopes much higher magnification and resolution Electron microscopes made the detailed study of cell ultrastructure possible 2
Comparison of Light, Transmission electron and Scanning Electron microscopy 3
Recall, that there are two basic categories of cells: Prokaryotic cells organisms in the Domain Archaea and Bacteria are prokaryotic in structure Eukaryotic cells plants, animals, fungi, etc.. Prokaryotic cells Very simple contain: Plasma membrane Cytoplasm Genetic control No nucleus prokaryotic chromosome is not enclosed in a membrane!!!!! 4
Eukaryotic cells True nucleus genetic material is surrounded by membrane. Typically larger than prokaryotic cells but still small Why are cells small? Large living things typically do not have larger cells? Why?? Plasma membrane Forms a selective barrier to allow the controlled passage of materials in and out of the cell Phospholipid bilayer with proteins Forms the surface area of a cell 5
Surface area regulates cell size Materials must pass in-out of cell. Must pass through plasma membrane Comparison of typical animal and plant cells Recall the three components that all share have in common: Plasma membrane Cytoplasm Genetic control We are going to survey generalized animal and plant cells Look for similarities and differences between the two 6
General Animal cell Plasma membrane Microvilli Flagellum Cytoplasm Mitochondrion Cytoskeleton Centrosome pair of centrioles General Animal cell Endoplasmic reticulum Rough ER Smooth ER Ribosomes Golgi complex Lysosome Peroxisome 7
General Animal cell Nucleus Nuclear envelope Nuclear pores Nucleolus chromatin General Plant cell Cell wall plasmodesmata Central vacuole Tonoplast-turgor pressure Chloroplast 8
A closer look at the nucleus Nuclear envelope Nuclear pores Nuclear pore complex Transport of materials Nucleolus Ribosome production Genetic material Chromatin Chromosomes During cell division Humans 23 pair of chromosomes in somatic cells; 23 single in gametes Why?????? A closer look at ribosomes Made of ribosomal RNA and proteins Large and small subunits form sandwich Carry out protein synthesis Not surrounded by a membrane Free ribosomes floating in the cytoplasm Synthesize proteins that have a function in the cytoplasm Bound ribosomes attached to ER or nuclear envelope Synthesize proteins for insertion into cell membranes, lysosomes, or export from cell 9
A closer look at the endomembrane system Endomembrane system includes the SER, RER, the nuclear envelope, the Golgi apparatus, various vesicles and vacuoles and the plasma membrane SER Synthesis of lipids, steroids, phospholipids Detoxification RER Important in protein synthesis produces more membrane for the cell Transport vesicles A closer look at the Golgi apparatus The cis face is located near the ER Transport vesicles from the ER move materials to the Golgi The trans face is located away from the ER Gives rise to vesicles which move away from the Golgi 10
Lysosomes found in animal cells Membranous sacs of hydrolytic enzymes for intracellular digestion Phagocytosis creation of food vacuole and subsequent digestion Autophagy recycles cellular components Vacuoles - storage sacs Food vacuoles Central vacuole found only in plant cells Tonoplast membrane Turgor pressure water Storage of electrolytes 11
Mitochondria Cristae Mitochondrial matrix Free ribosomes and mitochondrial DNA Site of aerobic cellular respiration and majority of ATP production Chloroplasts Found in plant cells only Site of photosynthesis within the cell Chlorophyll and other pigments Chloroplast DNA and ribosomes Thylakoid membranes Grana stacks of thylakoids Stroma fluid filled area outside the thylakoids 12
Elements associated with the cytoskeleton - Functions for support, motility and regulation Centrosome animals cells Pair of centrioles Creation of the mitotic spindle used during cellular division Cilia Flagella 13
Cell wall of plants Composed of primarily cellulose Structure for plant cell Plasmodesmata Connections between plant cells Middle lamella joins adjacent plant cells Plant cells Cellular junctions Plasmodesmata Animal cells Tight junctions Continuous seal Gap junctions Communication between cells Desmosomes rivets 14
All activities of cells must be coordinated The ability of the macrophage to recognize the harmful bacteria, locate them, capture them, and engulf them to be destroyed takes a coordinated effort 15