Lesson Overview. 7.2 Cell Structure

Transcription

1 7.2

2 Cell Organization The eukaryotic cell can be divided into two major parts: the nucleus and the cytoplasm. The cytoplasm is the fluid portion of the cell outside the nucleus. Prokaryotes do not have a nucleus

3 Cell Organization Organelles little organs. Example: mitochondria, golgi apparatus, endoplasmic reticulum

4 The Nucleus the nucleus is the control center of the cell. It contains nearly all the cell s DNA.

5 The Nucleus The nucleus is surrounded by a nuclear envelope composed of two membranes.

6 The Nucleus The nuclear envelope is dotted with thousands of nuclear pores, which allow material to move into and out of the nucleus.

7 Vacuoles Vacuoles large, saclike, membraneenclosed structures They store water, salts, proteins, and carbohydrates.

8 Vacuoles In plant cells the pressure of the vacuole increases their rigidity, making it possible for plants to support heavy structures such as leaves and flowers.

9 Vesicles Vesicles are used to store and move materials between cell organelles, as well as to and from the cell surface.

10 Lysosomes Lysosomes are small organelles filled with enzymes that function as the cell s cleanup crew. Lysosomes remove junk that might accumulate and clutter up the cell. istockphoto.com

11 Lysosomes breakdown of lipids, carbohydrates, and proteins into small molecules that can be used by the rest of the cell.

12 Lysosomes Break down organelles that have outlived their usefulness. Helps digest tissue to form fingers in the fetus Helps break down endometrial lining of the uterus to cause menstrual flow

13 The Cytoskeleton Gives eukaryotic cells their shape and internal organization. Microfilaments and microtubules are two of the principal protein filaments that make up the cytoskeleton.

14 Ribosomes small particles of RNA and protein found in the cytoplasm; they produce proteins. The instructions to make proteins come from DNA.

15 Endoplasmic Reticulum internal membrane system of the cell is known as the endoplasmic reticulum, or ER. This is where lipid components of the cell membrane are assembled, along with proteins and other materials that are exported from the cell. The ER is divided into smooth ER & rough ER.

16 Rough Endoplasmic Reticulum or Rough ER involved in the synthesis & modification of proteins It is called rough because of the ribosomes found on its surface.

17 Smooth Endoplasmic Reticulum or Smooth ER Is called smooth ER because ribosomes are not found on its surface. It contains enzymes that make membrane lipids and the detoxify drugs.

18 Golgi Apparatus Proteins produced in the rough ER move to the Golgi apparatus It appears as a stack of flattened membranes.

19 Golgi Apparatus It modifies, sorts, and packages proteins and other materials from the ER for storage in the cell or release outside the cell.

20 Golgi Apparatus From the Golgi apparatus, proteins are shipped to their final destination inside or outside the cell.

21 Organelles That Capture and Release Energy The primary source of energy for plants is the SUN Your body cells get energy from food (plants and animals). Chloroplasts and mitochondria are both involved in energy conversion processes within the cell.

22 Chloroplasts Plants and some other organisms contain chloroplasts. Chloroplasts capture energy from sunlight and convert it into food that contains chemical energy. CHLOROPLASTS are the biological equivalents of solar power plants

23 Photosynthesis Photosynthesis process where plants make carbohydrates and oxygen using sunlight energy, carbon dioxide, and water. e/biology_place/biocoach/image s/photosynth/photo1.gif

24 Chloroplasts Two membranes surround chloroplasts. Inside the organelle are large stacks of other membranes, which contain the green pigment chlorophyll.

25 Mitochondria Nearly all eukaryotic cells, including plants, contain mitochondria. Mitochondria are the power plants of the cell. They convert the chemical energy stored in food into compounds that are more convenient for the cell to use.

26 Mitochondria Two membranes an outer membrane and an inner membrane enclose mitochondria. The inner membrane is folded up inside the organelle.

27 Mitochondria In humans, all or nearly all of our mitochondria come from the cytoplasm of the ovum, or egg cell. You get your mitochondria from Mom!

28 Mitochondria Chloroplasts and mitochondria contain their own genetic information in the form of small DNA molecules. The endosymbiotic theory suggests that chloroplasts and mitochondria may have descended from independent microorganisms.

29 Cellular Boundaries The barrier surrounding the cell is the cell membrane It (1) regulates what enters and leaves the cell and also (2) protects and (3) supports the cell.

30 Cellular Boundaries Plant cells and most prokaryotes have a strong supporting layer around the membrane known as a cell wall. The main function of the cell wall is to provide support and protection for the cell.

31 Cell Walls Many prokaryotes, plants, algae, and fungi, have cell walls. Animal cells do not have cell walls. Cell walls lie outside the cell membrane and most are porous enough to allow water, oxygen, carbon dioxide, and certain other substances to pass through easily.

32 Lipid bilayer It is a double-layered sheet found in nearly all cell membranes. It gives cell membranes a flexible structure and forms a strong barrier between the cell and its surroundings

33 Lipid bilayer Composed of phospholipids The fatty acid portions of such a lipid are hydrophobic, or water-hating, while the opposite end of the molecule is hydrophilic, or waterloving.

34 The Fluid Mosaic Model Most cell membranes contain protein molecules that are embedded in the lipid bilayer. Carbohydrate molecules are attached to many of these proteins.

35 The Fluid Mosaic Model Fluid- because the proteins in the lipid bilayer can move around and float among the lipids. MOSAIC Mosaic- because so many different kinds of molecules make up the cell membrane 5dtW4

36 The Fluid Mosaic Model Some of the proteins form channels and pumps that help to move material across the cell membrane. Many of the carbohydrate molecules act like chemical identification cards, allowing individual cells to identify one another.

37 The Fluid Mosaic Model If a substance is unable to cross a membrane, the membrane is said to be impermeable to it. If a substance is able to cross a membrane, the membrane is said to be permeable to it. Although many substances can cross biological membranes, some are too large or too strongly charged to cross the lipid bilayer.

38 Most biological membranes are selectively permeable, meaning that some substances can pass across them and others cannot. Selectively permeable membranes are also called semi-permeable membranes.