Cell Structure Chapter 7

7-1: Introduction to Cells

The Discovery of Cells In 1665, Robert Hooke, an English scientist, used a simple microscope (which magnified objects 30 times their normal size) to observe “little boxes” in thin slices of cork. He called the boxes “cells” because they reminded him of the small rooms in which monks lived.

The Discovery of Cells In 1675, Anton van Leeuwenhoek, a Dutch scientist, used a stronger microscope (that could magnify objects 300-fold) He named pond water creatures “animalcules” or “tiny animals”. First to observe living cells

Cell Theory 1. All living things are made up of one or more cells. 2. Cells are the basic units of structure and function in organisms. 3. All cells arise from existing cells.

Looking at Cells Cell size is limited by a cell’s surface area-to- volume ratio Larger cells often have shapes that increase the surface area available for exchange

Similarities and Differences in Prokaryotic and Eukaryotic Cells ProkaryoticEukaryotic Average Cell Size 1-10 µm µm Cell WallYESSOMETIMES Cell MembraneYES NucleusNOYES CytoplasmYES DNAYES, in cytoplasm YES, in nucleus Continuation on next slide

Similarities and Differences in Prokaryotic and Eukaryotic Cells ProkaryoticEukaryotic RibosomesYES Membrane Enclosed Organelles NOYES Mode of Locomotion One or more flagella One or two flagella or cilia Found in --Bacteria onlyFungi, protists, plants, animals

7-2: Inside the Eukaryotic Cell

The Framework of the Cell Cytoskeleton – helps the cell move, keep its shape, and organize its parts  Microfilaments and microtubules are two types of cytoskeletons

Directing Cellular Activity Nucleus – membrane bound structure that contains the cell's hereditary information and controls the cell's growth and reproduction  The nucleus (nuclei – plural) houses deoxyribonucleic acid (DNA) Genetic material in cells Has information to make proteins

Directing Cellular Activity Nuclear membrane – a double membrane that surrounds the nucleus Pores – openings in the outer nuclear membrane that allow substances to enter and leave the nucleus

Directing Cellular Activity Nucleolus (nucleoli) – small, dark-stained, round structures that makes ribosomes Chromatin – DNA is in thread-like form; the cell is not dividing Chromosome – condensed chromatin; forms a “X” structure during cellular division

Directing Cellular Activity Ribosomes – Organelles that help in the synthesis of proteins  “Free” ribosomes make proteins that remain inside the cell  “Bound” ribosomes make proteins that are exported from the cell

Directing Cellular Activity Cytoplasm – the gel-like substance found between the cell membrane and the nucleus

Directing Cellular Activity Centriole – one of a pair of organelles that are found in animal cells that function in the formation of spindle fibers during cell division

Protein Processing Vesicle – (means “small vessel”) Sac-like membrane that helps store and transport products produced by cells

Protein Processing The endoplasmic reticulum and the Golgi apparatus are organelles that prepare proteins for extracellular export Endoplasmic reticulum (ER) – a network of membranes throughout the cytoplasm of the cell

Protein Processing Two types of ER  Rough ER – proteins are made in ribosomes and then packaged into vesicles  Smooth ER – synthesize lipids in the cell and helps in the detoxification of harmful substances in the cell

Protein Processing Golgi complex – responsible for sorting and correctly shipping the proteins produced in the ER  Resembles a post office in cells

Storage and Maintenance Lysosome – a vesicle that contains specific enzymes that breaks down large molecules They also help recycle materials in the cell by digesting old, damaged, or unused organelles Lysosomes are in animal cells

Storage and Maintenance Mitochondrion (mitochondria = plural) – an organelle that uses energy from organic compounds to make ATP

Mitochondria and chloroplasts have their own DNA

Storage and Maintenance Vacuole – an organelle that stores water, ions, nutrients, and wastes; it can also store toxins and pigments  Animal cells have small vacuoles  When water fills the central vacuole (only in plant cells), it makes the cell rigid, allowing the plant to stand upright.

Storage and Maintenance Some protists have contractile vacuoles, which pump excess water out of the cell

Storage and Maintenance Chloroplast – an organelle that uses light energy to make sugar from carbon dioxide and water

Plant Cell vs. Animal Cell Cell wall – provides additional support for certain cells; they have cellulose which aids in its structure

Plant Cell vs. Animal Cell Organelles that are exclusively found in plant cells  Cell wall  Central vacuole  Chloroplast Organelles that are exclusively found in animal cells  Lysosome  Centriole

Picture of animal cell vs. plant cell

Cellular Movement Flagella – long finger-like projections that push cells forward by snakelike wriggling

Cellular Movement Cilia – short hair-like projections of certain cells that beat in a regular fashion to create currents that sweep materials along

7-3: From Cell to Organism

Levels of Organization Cell – the smallest unit of life Tissue – group of cells that work together and have a common function Organ – group of tissues that work together… Organ system – group of organs… Organism – group of organ systems…

Cellular Differentiation Cellular differentiation – The normal process by which a less specialized cell develops or matures to possess a more distinct form and function