Cell Structure and Function

Attributes of cells A. Plasma membrane B. DNA C. Cytoplasm D. Obtain energy and nutrients from their environment

1. 1–100µm 2. Why is there a limit to cell size? a. Surface-to-volume ratio b. Distance from surface to center Cell Size

adult human tallest trees chicken egg frog embryo most eukaryotic cells mitochondrion most bacteria virus proteins atoms diameter of DNA double helix

Prokaryotic—no nucleus, circular DNA, ribosomes Eukaryotic—larger, nucleus, linear chromosomes, membranous organelles Cell types

Prokaryotic Cells Have no membrane-bound organelles Include true bacteria On earth 3.8 million years Found nearly everywhere Spores in each breath; intestines Naturally in soil, air, hot springs

ribosomes cell wall plasma membrane food granule prokaryotic flagellum cytoplasm nucleoid (DNA)

Eukaryotic Cells Have numerous internal structures Various types & forms Plants, animals, fungi, protists Multicellular organisms

flagellum cytoplasm rough endoplasmic reticulum ribosome microtubules lysosome mitochondrion Golgi complex plasma membrane intermediate filaments vesicle smooth endoplasmic reticulum free ribosome vesicle nuclear pore chromatin (DNA) nucleolus nuclear envelope nucleus

chloroplast central vacuole rough endoplasmic reticulum ribosomes microtubules (part of cytoskeleton) cell wall mitochondrion Golgi complex plasma membrane intermediate filaments smooth endoplasmic reticulum free ribosome vesicle nuclear pore chromatin nucleolus nuclear envelope nucleus

Eukaryotic cell structure Nucleus is control center of the cell 1. Membrane bound (nuclear envelope) 2. Contains nucleoli; synthesizes ribosomal RNA 3. DNA in chromosomes (DNA and proteins)

nuclear pores chromatin nucleolus nuclear envelope

nuclear pores nucleus

chromosome chromatin

0.05 micrometers

Eukaryotic cell structure Organelles Endoplasmic reticulum consists of folded membranes attached to the nucleus Rough ER is site of protein synthesis and protein secretion

0.5 micrometers smooth endoplasmic reticulum vesicles ribosomes rough endoplasmic reticulum 0.5 micrometers

Eukaryotic Cell Structure Organelles (cont.) Ribosomes assemble amino acid into polypeptide chains a. Associated with the ER b. Composed of RNA and proteins

ribosomes rough endoplasmic reticulum

0.5 micrometers smooth endoplasmic reticulum vesicles

Eukaryotic Cell Structure Organelles (cont.) Golgi apparatus are membranous sacs associated with ER a. Processing and transport of proteins, lipids b. Synthesis and transport of polysaccharides

Golgi complex vesicles from ER vesicles leaving Golgi complex

Eukaryotic cell structure Organelles (cont.) Lysosomes are Golgi-derived vesicles containing digestive enzymes

Golgi complex vesicles from ER vesicles leaving Golgi complex

Eukaryotic Cells: Organelles Energy sources for cell activities Mitochondria provide energy for cellular functions (respiration) a. Membrane bound, numerous b. Matrix/cristae c. Have their own DNA and ribosomes; self-replicate

5 micrometers

Eukaryotic Cells: Organelles Energy sources for cell activities Chloroplasts—function in photosynthesis 1) Green—contain chlorophyll pigment 2) Stroma/grana (thylakoid stacks) 3) Have their own DNA and ribosomes; self-replicate 4) Up to 100 per cell

Eukaryotic Cells: Organelles Cytoskeleton Internal infrastructure Surface structures extensions of the plasma membrane aid in movement of simple organisms

tubulin subunit actin subunits subunit

Prokaryotes & Eukaryotes Similarities & differences Both surrounded by plasma membrane, but very different Prokaryotes – Archaebacteria and Eubacteria Eukaryotes – everything else

Evolution of Eukaryotic cell Endosymbiotic Hypothesis Similarities between bacteria, mitochondria and chloroplasts Self-reproducing by binary fission Size of organism and genome Single circular naked DNA Proportion of (G & C) to (A & T) Same sized ribosome Protein synthesis inhibited by antibiotics Enzymes for synthesis of DNA, RNA and protein Electron transport system

Plant & Animal Cells Similarities Both constructed from eukaryotic cells Both contain similar organelles Both surrounded by cell membrane

Plant & Animal Cells Differences Plants have Cell wall – provides strength & rigidity Have chloroplasts, photosynthetic Animals have Other organelle not found in plants (lysosomes formed from Golgi) Centrioles, important in cell division

Brief Look at Viruses Viruses are acellular Not considered to be living Cause serious diseases in most organisms