Cell Structure & Function

Robert Hooke (1600s) named the cell after viewing cork under m’scope

At 40x tattoo ink in dermis of skin

Comparing Prokaryotic and Eukaryotic Cells Basic features of all cells: –Plasma membrane –Semifluid substance called cytosol –Chromosomes (carry genes) –Ribosomes (make proteins) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

2 Types of Cells Prokaryotes: earliest cells; Have NO NUCLEUS Eukaryotes: modern cells/most cells( all but bacteria) HAVE A NUCLEUS

Fig. 6-6 Fimbriae Nucleoid Ribosomes Plasma membrane Cell wall Capsule Flagella Bacterial chromosome (a)A typical rod-shaped bacterium (b)A thin section through the bacterium Bacillus coagulans (TEM) 0.5 µm

Sickle Cell Anemia *note misshapen RBC

Cell Theory 1.All living things are made of cells. 2.Cells are the basic unit of life 3.New cells come from existing cells -Schleiden, Schwann, Virchow

Functions of Organelles

Cytoplasm (Cytosol) Thick, clear gel-like substance found throughout cell Supports the organelles

Nucleus “control center” of cell Contains the chromosomes (genetic info.= DNA*) Has all instructions to make new proteins *DNA from both parents found here

Nucleolus Center of nucleus Site of ribosome synthesis (ribosomes are made here)

Fig. 6-UN1a Cell Component Structure Function Concept 6.3 The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes Nucleus Surrounded by nuclear envelope (double membrane) perforated by nuclear pores. The nuclear envelope is continuous with the endoplasmic reticulum (ER). (ER) Houses chromosomes, made of chromatin (DNA, the genetic material, and proteins); contains nucleoli, where ribosomal subunits are made. Pores regulate entry and exit os materials. Ribosome Two subunits made of ribo- somal RNA and proteins; can be free in cytosol or bound to ER Protein synthesis

Fig Nucleolus Nucleus Rough ER Nuclear lamina (TEM) Close-up of nuclear envelope 1 µm 0.25 µm Ribosome Pore complex Nuclear pore Outer membrane Inner membrane Nuclear envelope: Chromatin Surface of nuclear envelope Pore complexes (TEM)

Chromosomes Contain genetic information/DNA Chromatin combines to form Humans have 46 chromosomes or 23 pairs

Fig. 15-1

Fig X Y

Endoplasmic Reticulum Extensive system of tubules and membranes –2 Types: 1.Smooth ER 2.Rough ER

Smooth ER Synthesis of lipids (cholestrol) Breaks down/metabolizes carbohydrates Packages enzymes for secretion De-toxification of alcohol in liver ER

Fig Smooth ER Rough ER Nuclear envelope Transitional ER Rough ER Smooth ER Transport vesicle Ribosomes Cisternae ER lumen 200 nm

Fig Cytosol Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit Small subunit Diagram of a ribosome TEM showing ER and ribosomes 0.5 µm

Rough ER Has ribosomes attached One of the sites of protein assembly

Ribosomes Site of protein synthesis Made of RNA + protein Means: proteins are made here Free Ribosomes: NOT attached to ER Bound Ribosomes: attached to ER

Cell Membrane (plasma membrane) Support Protection Regulates which substances enter & exit = Selectively permeable

Fig. 6-7 TEM of a plasma membrane (a) (b) Structure of the plasma membrane Outside of cell Inside of cell 0.1 µm Hydrophilic region Hydrophobic region Hydrophilic region PhospholipidProteins Carbohydrate side chain

Fig EXTRACELLULAR FLUID Collagen Fibronectin Plasma membrane Micro- filaments CYTOPLASM Integrins Proteoglycan complex Polysaccharide molecule Carbo- hydrates Core protein Proteoglycan molecule Proteoglycan complex

What might ENTER a cell? Oxygen Dissolved nutrients Potassium and other ions water

Vacuoles Storage of –Water –Dissolved nutrients –Even Waste **animals have few, very small

Fig Central vacuole Cytosol Central vacuole Nucleus Cell wall Chloroplast 5 µm

Central Vacuole Plants have a large central vacuole. Takes up most of plant cell –Supports –Turgor Pressure –“Wilting” process: how?

Nuclear Membrane Protects nucleus (why necessary?) Has Nuclear Pores: holes to allow substances to enter/exit

Lysosomes Animal Cells Bags of hydrolytic enzymes Digests old cell organelles

Cytoskeleton System of protein fibers (Microtubules, microfilaments) 1.Gives cell shape 2.Supports cell 3.Helps move organelles

Fig. 6-1

Golgi Apparatus Golgi Body Proteins are modified and packaged here for secretion “warehouse/UPS” of cell Lysosomes are made here

Fig cis face (“receiving” side of Golgi apparatus) Cisternae trans face (“shipping” side of Golgi apparatus) TEM of Golgi apparatus 0.1 µm

Fig Smooth ER Nucleus Rough ER Plasma membrane cis Golgi trans Golgi

Mitochondria “powerhouse of cell”= energy is produced Site of cellular (aerobic) respiration (ATP is made) Was once an independent, free-living organism

Fig Free ribosomes in the mitochondrial matrix Intermembrane space Outer membrane Inner membrane Cristae Matrix 0.1 µm

More active cells have more mitochondria- WHY? Ex: muscle cells have more Has a membrane surrounding And DNA of its own! mtDNA- inherited from mother/materlineal Used in forensics (sometimes)

Endosymbiont Theory: Idea that….. 1.Chloroplasts & mitochondria were once free-living 2.Moved into eukaryotic cell 3.Became an organelle of cell

Why do we think this? Both chloroplasts & mitochondria have: a)Outer membrane b)Energy source/function c)Both have bits of genetic material

Fig µm Chloroplast Peroxisome Mitochondrion

Chloroplast Plant Cells Located in middle of leaf tissue Site of photosynthesis green- chlorophyll Was once free-living, independent *has maternal DNA ( interesting!)

Fig Ribosomes Thylakoid Stroma Granum Inner and outer membranes 1 µm

Cell Wall Plants only Support Protection Made of cellulose: strong carbohydrate

Fig Secondary cell wall Primary cell wall Middle lamella Central vacuole Cytosol Plasma membrane Plant cell walls Plasmodesmata 1 µm

Centrioles Animal cells Helps move chromosomes apart during mitosis

Cilia and Flagella Protein fibers Cilia- short fibers; all over Flagella- long fibers; 1 or 2 purpose: locomotion (movement) Ex: paramecium, spermatozoa

Fig µm Direction of swimming (a) Motion of flagella Direction of organism’s movement Power strokeRecovery stroke (b) Motion of cilia 15 µm

How Are Plant Cells and Animal Cells Different? Plants: Chloroplasts Cell walls Central vacuole Green: chlorophyll None Rectangular shape Animals None Few, smaller None Lysosomes Different shapes More mitochondria