Cell MembraneIt also connects the the endoplasmic reticulum, and the nuclear membrane. In the image below we have colored the membrane to highlight its composition. The yellow represents the phospholipids. The purple represents the membrane proteins
Cell Membrane• The Cell membrane performs a number of critical functions for the cell. It regulates all that phospholipids enters and leaves the cell; in multicellular organisms it allows self recognition. In order to understand the function of the cell membrane you must understand its structure.
Cell MembraneClose-up • Here we see a cross section of the cell membrane you should notice two different structures: The phospholipids are the round yellow structures with the blue tails , the proteins are the lumpy structures that are scattered around among the
This is a simple representationof a phospholipid. the yellowstructure represents theHYDROPHILLIC or water lovingsection of the phospholipid. Theblue tails that come off of thesphere represent theHYDROPHOBIC or waterfearing end of the Phospholipid.Below is a structural model of aphospholipid that explains whatthese terms mean.
• Cell walls are Cell Wall the rigid structure found surrounding plant cells. They provide support for the plant
Cytoplasm• The term cytoplasm refers to everything between the cell membrane and the nuclear envelope. It consists of primarily of water. It also contains various organelles as well as salts, dissolved gasses and nutrients.
NUCLEUS- nuclear envelopeThe nuclear envelope is a double membrane. Is has 4 phospholipid layers. It is also has large pores through which materials pass back and forth.
NucleusThe headquarters of the cell. It is a large dark spot in EUKARYOTIC cells. It controls all cell activity. Close up you will see that the nuclear membrane has many pores. The nuclear membrane is continuous with the E.R.
With the outer membrane removed it ismuch easier to see the contents of thenucleus. The thick ropy strands are the CHROMATIN . The large solid spot is the NUCLEOLUS . The nucleolus is a knot of chromatin. It manufactures ribosomes.
ChromatinWithin the nucleus are found chromatin and a structure called the nucleolus. Chromatin is DNA in its active form. It consists of DNA looped around histone proteins. The nucleolus is a knot of chromatin. It is the nucleolus that
Endoplasmic Reticulum • Smooth, no ribosomes • rough, has ribosomes
Smooth E.R.• The endoplasmic reticulum is a series of double membranes that loop back and forth between the cell membrane and the nucleus.• These membranes fill the cytoplasm but you cannot see them because they are very transparent. There are two distinct types of E.R.: The rough E.R. has ribosomes and is the site of protein synthesis; the smooth E.R. has no ribosomes•
The endoplasmicR.E.R. reticulum is a series of double membranes that loop back and forth between the cell membrane and the nucleus. These membranes fill the cytoplasm but you cannot see them because they are very transparent.
• The ribosomes are the organ- Ribosome elles which manufacture proteins. They are made of two separate parts. These structures are both made of ribosomal RNA.
The golgi body is Golgi Apparatus responsible for packaging proteins for the cell. Once the proteins are produced by the rough E.R. they pass into the sack- like cisternae that are the main part of the golgi body. These proteins are then squeezed off into the little blebs which drift off into the cytoplasm.
Lysosomes are called Lysosome suicide sacks. They are produced by the golgi body. They consist of a single membrane surrounding powerful digestive enzymes. From this screen you can cut the lysosome and move it around.
Lysosomes• With the outer membrane removed it is much easier to see the contents of the lysosome. Those lumpy brown structures are digestive enzymes.
"suicide sacks” • They dissolve bacteria and other foreign bodies. Under some conditions the lysosomes in a cell will break open and a cell will self destruct in a process called autolysis (giving rise to the name "suicide sacks").
VacuoleVacuoles are largeempty appearingareas foundin the cytoplasm.They are usuallyfound in plant cellswhere they storewaste. As a plant cellages they get larger.In mature cells theyoccupy most of thecytoplasm.
MicrofilamentThese are hair like extensions off of the cell membrane. Cilia tend to be small and numerous and flagella tend to be large &few. They beat back and forth rhythmically. In unicellular organisms their job is locomotion. In large multicell organisms their role is to move fluid past the cell. Notice the 9+2 arrangement of the microtubles.
Microtubule• Centrioles are found only in animal cells. They function in cell division. Zoom in and notice the 9 groups of 3 arrangement of the protein fibers.
The MITOCHONDRION isthe powerhouse of the cell. It isthe site of respiration. It has adouble membrane. From this viewyou can see very little >>>>>>>>>>
The outer membrane is cut to get a better look. With the outer membrane removed it is much easier to see the contents of the mitochondrion. The white folded structure is the inner membrane. Most of AEROBIC RESPIRATION occurs along this membrane. Get a really good look by cutting the inner membrane. >>>next slide>>>>>
The inner membranes is ruffled. It hasa very large surface area. These ruffles arecalled cristae. Mitochondria have theirown DNA and manufacture some theirown proteins. It is thought that themitochondrion evolved from symbioticbacteria that took up residence insidethe first eukaryotic cells.
• Plastids are large organelles found on Plastids plants and some protists but not in animals or fungi. They can easily be seem through a light microscope. The other class of plastid are called leucoplasts (colorless plastids); they usually store food molecules. Included in this group are amyloplasts or starch plastids shown here in potato root cell.
PLASTIDS- Chloroplast• Chloroplasts • represent one group of plastids called chromoplasts (colored plastids).
The chloroplast is thesite of photosynthesis.It consists of a doublemembrane. Cut theouter membrane to geta better look inside.With the outer membrane removed it is mucheasier to see the contents of the chloroplast.The stacks of disk-like structures are calledthe GRANA. The membranes connectingthem are the THYLAKOID MEMBRANES.
Grana and Thylakoid Membranes • The membranes that you seeDissolve the Remaining membrane and zoom in here are theto get a better look. site of photosynthesis. It is here that the energy harnessing process of photosynthesis occurs.