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An Overview of the Cell With a focus on Plant and Animal Cell Structures.

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Presentation on theme: "An Overview of the Cell With a focus on Plant and Animal Cell Structures."— Presentation transcript:

1 An Overview of the Cell With a focus on Plant and Animal Cell Structures

2 Types of Cells O There are two categories all cells can be divided into: O Prokaryotic cells do not have a membrane-bound nucleus and the genetic material is scattered throughout the rest of the cell. (doesn’t have a true nucleus) O Eukaryotic cells have a nucleus surrounded by a nuclear membrane to contain all genetic material. (has a true nucleus) O Cells vary in size, shape and function.

3 Prokaryotic vs Eukaryotic Cells

4 The Nucleus O Is the cell’s control center and coordinates all cell activities. O The nucleus contains chromosomes which are threadlike structures that contain our genetic code. These chromosomes are made of proteins and deoxyribonucleic acids (DNA) O Chromatin: The complex of DNA and proteins that make up a eukaryotic chromosome. When the cell is not dividing, chromatin exists as a mass of long thin fibres that are not visible with a light microscope. O Chromosomes: As the cell prepares to divide (reproduce), the stringy, entangled chromatin coils up and becomes thick enough to be seen as separate structures called chromosomes.

5 The Nucleus (and Rough Endoplamic Reticulum)

6 The Nuclear Membrane Separated from the rest of the cytoplasm by a double membrane. Pores in the nuclear envelope allows RNA and other chemicals to pass through but keeps the DNA inside

7 Nucleolus O A small spherical structure located inside the nucleus. O It is believed that the nucleolus creates ribosomal ribonucleic acid (rRNA) which directs the formation of ribosomes.

8 The Cell Membrane O The cell membrane (plasma membrane) surrounds the cell, giving it a definite shape and boundary. It is selectively permeable, so it controls what enters and exits the cell.

9 Cell Wall O In many organisms the plasma membrane is not the outermost boundary. O In plants, most algae, fungi and bacteria, there is a cell wall that lies outside the plasma membrane. O In plants it is made of cellulose and has spaces for water, ions and particles to pass through.

10 O It is NOT selectively permeable but does offer protection and support for the cell. Some plant cells have an additional secondary wall with a middle lamella in between that contains a sticky pectin to hold cells together.

11 The Cytoplasm O The cytoplasm is the gel-like substance inside the cell. O Cytoplasm- 70% water - 30% proteins, fats, carbohydrates and other ions. O Composition is always changing due to osmosis and diffusion. O The cytoplasm houses the working “organs” of the cell called organelles.

12 Mitochondria O Mitochondrion (singular) Mitochondria (plural) O Are oval-shaped organelles and are the “powerhouses” of the cell. O Mitochondria contain their own DNA O They provide the body with needed energy in a process called cellular respiration.

13 O Sugar molecules are combined with oxygen to form carbon dioxide and water with a release of energy. O Energy is not made in the mitochondrion rather the breakdown of glucose sugar releases energy. O Energy is available for processes such as: O Muscle contraction O Synthesis of new molecules O Cellular transport

14 O Two separate membranes – a smooth outer membrane and a folder inner membrane. O Cristae – fingerlike projections of the folded inner membrane. Each contains special enzymes to help breakdown glucose.

15 Ribosomes O Smallest organelle in the cell. O Site of protein synthesis. O Proteins are the molecules that makes up cell structure. O Cell growth and reproduction require constant synthesis of proteins. O In the nucleus, DNA sends messenger molecule to produce protein in ribosomes of the cell.

16 O Location: found both scattered throughout the cytoplasm and attached to endoplasmic reticulum.

17 Endoplasmic reticulum O A series of canals that carry materials throughout the cytoplasm. O Composed of parallel membranes. O 2 types: 1. Rough endoplasmic reticulum 2. Smooth endoplasmic reticulum

18 Rough Endoplasmic Reticulum O Organelle with a double membrane and ribosomes attached. O Extends from the nuclear membrane to the cell membrane. O Transports proteins made by the ribosomes to the Golgi apparatus.

19 Smooth Endoplasmic Reticulum O Double membrane bound organelle without ribosomes. O Also extends throughout the cell. O Produces lipids for the cell.

20 Golgi Apparatus O Appears like a stack of pancakes. O They are membranous sacs piled on top of each other. O Function: O To package, modify and store proteins produced by ribosomes on the rough endoplasmic reticulum. O To release large molecules (hormones, enzymes) by exocytosis.

21 O Golgi apparatus migrates towards the plasma membrane where small packets (called vesicles) are released and pass through plasma membrane by exocytosis. O The golgi apparatus will also form lysosomes

22 Lysosomes O Formed by exocytosis of vesicles from Golgi apparatus and are smaller than mitochondria. O They are sac-like structures that contain digestive enzymes to break down large molecules and cell parts within the cytoplasm. O Only found in animal cells

23 O Purpose: O The break down cell “food” to use as an energy source. O As a defense mechanism for the immune system. O The Immune Response O Lysosomes destroy harmful substances that find their way into the cell. O Example: White blood cells phagocytise foreign particles. Lysosomes then release digestive enzymes to destroy the invader.

24 O Lysosomes are also known as “suicide sacs”. O Body cells have a certain lifespan after which they die and must be cleaned up. Digestive enzymes in lysosomes clean up cell parts after body cells die.

25 Vacuoles O Vacuoles are fluid-filled, membrane-bound structures that store substances produced by the cell for future use. O They are reservoirs for sugars, minerals, proteins, water and wastes. O Gives plant cells physical support. O Plant cells have large, central vacuoles. O Animal cells have many smaller vacuoles.

26 Cytoskeleton O Microfilaments are threadlike structures in the cytoplasm that help provide shape & movement. O Microtubules are tube-like fibres (made of protein) that transport materials through the cytoplasm – also found in flagella & cilia.

27 Cilia and Flagella O A flagellum is a whip like tail O that aids in movement O Flagella spin like a propeller O Cilia (cilium)are shorter, hair like structures that aid in movement and moving materials.

28 Centrioles O Composed of nine bundles of three microtubules. O Found only in animal cells. O Play a key role in cell division.

29 Plastids O Plastids are “chemical factories” and “storehouses” for food and other pigments in plant cells O Only found in plant cells! O Chloroplasts are plastids that contain the green pigment chlorophyll that is used for photosynthesis. O Chromoplasts- store orange and yellow pigments O Amyloplasts- colourless plastids that store starch

30 O Plastid structure: O Made of a double membrane O Packets of chlorophyll inside which taps into the Sun’s energy to make sugar.


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