Cell Structure and Function History of Cell Biology

Cell Structure and Function

History of Cell Biology • The discovery of cells – All living things are made up of one or more cells – Cells carry out all the processes of life

• Robert Hooke – Nature with light microscope – Cork bark from oak tree • observed little boxes reminded him of monk quarters • Leeuwenhoek – First to observe living cells from microscope – 10 X of Hooke’s instruments

Cell Theory 150 years after the discovery of cells 1. All living organisms are made of one or more cells 2. Cells are the basic units of structure and function in an organism 3. Cell come only from the reproduction of existing cells

Introduction to Cells Cell diversity • Variety of shapes and sizes • Form follows function

Cell Size • Size varies • Limited by the relationship of the cell’s outer surface area to its volume – Surface area : volume ratio • Too small of surface area compared to volume of the cell – Material would not enter or leave cell quickly enough

Basic Parts of a Cell • Plasma membrane (cell membrane) – Barrier between inside and outside of cell • Cytoplasm – Cytoskeleton, organelles, fluid • DNA – Regulating functions and reproduction • Ribosomes – Help in the production of Proteins

Two Cells Types • Prokaryotes • Eukaryotes

Prokaryotes • Lack membrane – bound organelles • Have genetic information • Bacteria and Archea

Eukaryotes • One or more cells • Have nucleus and organelles – Membrane bound structures that perform specific functions

Cell Membrane and Organelles • Cell membrane – Semi – permeable – Phospholipid bilayer – Polar hydrophilic (water – loving) head – Point outward/inward towards water • 2 nonpolar hydrophobic (water – fearing) fatty acid tails – Tails point inward away from the water – Animal cells also have sterols (type of lipid) • Firm membrane and prevents freezing

Membrane Proteins Found within the lipid bilayer • Cell – surface marker – Glycoprotein identifies cell • Receptor protein – Recognizes and binds substances outside of cell • Transport protein – Helps substances move across the membrane • Enzyme – Assists in chemical reaction inside the cell

En e m zy

Cytoskeleton • Thin tubules and filaments in cytosol – Microtubules • Maintain cell shape – Microfilaments • Cell movement – Intermediate • Anchor organelles • Cilia and Flagella • Centrioles

Nucleus • Nuclear envelope – Nucleolus • Ribosomes – made of RNA and aids in protein synthesis

Mitochondria • Transfer energy from organic molecules to make ATP • 2 membranes – Outer – Inner (site of energy production) • m. DNA – More m. DNA can be made only from mitochondria • Endosymbiosis

Ribosomes • Non – membrane bound organelle made of RNA and proteins • Builds protein • Free or attached to endoplasmic reticulum

Endoplasmic Reticulum • Intercellular highway of tubes and sacs • Two types – Rough ER • Covered with ribosomes • Produces phospholipids and proteins – Smooth ER • Not found in abundance • Build lipids and steriods • Help detoxify

Golgi Apparatus • Receive vesicles from ER containing proteins • Modify received material and tag it for delivery

Vesicles • Small spherical sac made of a single cell membrane • Migrate and merge with cell membrane • 3 types of vesicles – Lysosomes (digestive enzymes) – Peroxisomes (abundant in liver and kidney cells) – Contractile vacuole (plant cells hold excess water)

Protein Synthesis 1. Assembled by ribosomes on the Rough ER 2. Vesicles transport proteins to the Golgi Apparatus 3. Golgi modifies proteins and packages them in vesicles 4. Vesicles release proteins outside of the cell

Plant Cells • Cell walls – Rigid layer outside of cell membrane • Central vacuoles • Plastids – chloroplast • Photosynthesis • endosymbiosis – Other contain pigments and starch storage