Cell Boundaries, Lecture notes of Cell Biology

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Cell Membrane

• Double layer of phosholipids
• Controls movement of materials in and out of cells
• Selectively permeable because it only allows certain materials into and out of the cell.

• This membrane is composed of two main groups of organic molecules: lipids and proteins.

Lipids:

• The lipid bilayer
  • the phosphate “head”; is polar is attracted to water (hydrophilic)
• the two “tails”; the hydrocarbon chains are nonpolar and repelled by water (hydrophobic)

All cells can be

divided into two groups

• Prokaryotes
• Cells that DO NOT contain a nucleus - Eukaryotes - Cell that DO contain a nucleus and many specialized “organelles”

Size of a bacterium Compared to a eukaryotic cell

Cells

ALL cells have these 3 things:

1 - Cell Membrane

2 – Cytoplasm

3 – DNA

Nucleus

• Membrane enclosed

structure

• Contains the cells

genetic material

(DNA)

• The nucleus directs

the cells activities

• Nuclear envelope: membrane composed of thousands of pores that surrounds the nucleus
• Nucleolus – dense region
• within the nucleus
• where ribosomes are
• produced.

 Cytoskeleton – Network of protein filaments that help a cell maintain shape

• Mitochondrion

converts chemical energy stored in food into the energy molecule Adeosine Triphosphate (ATP).

◊ Rough Endoplasmic Reticulum

• Membrane with ribosomes for making proteins.
• Golgi Apparatus – Modifies/packages molecule for export out of cell
• Note- It is near the cell

membrane

Organelles only found in Animal Cells

Lysosome – contains enzymes for digesting or recycling molecules

Organelles only found in Plant Cells

• Central Vacuoles - Storage units of cells. Very large in plants for holding water.

• Chloroplast – uses energy from the sun to convert CO2 molecules into carbohydrates ub the process called photosynthesis.

VIRUSES

Chapter 19-

19-2 What is a Virus?

• Core of DNA or RNA; genetic material surrounded by a protein coat (Capsid).
• Can reproduce only by infecting living cells – once inside the cell, they use the machinery of the cell to produce more viruses
• Very small – need an electron microscope to see