Cell Structure and Function

1. Cell Structure and Function

2. Levels of Organization Organism Organ System Organ Tissues Organelles Cells

3. Cells • A cell is the smallest unit that is capable of performing all 8 life functions. • MRS C GREN

4. Cells • The size & shape of a cell relates to its function. • Two main types of cells: • Prokaryotic • Eukaryotic

5. Prokaryotic Cells • Cells that lack a cell nucleus, or any other membrane-bound organelles. • Chromosome is a simple DNA chain with the ends joined to form a circle.

6. Prokaryotic Cells • Most are unicellular, but some prokaryotes are multicellular. • E.g . bacteria, blue-green algae

7. Eukaryotic Cells • Higher organisms whose cells are arranged into complex structures enclosed within membranes. • The chromosome is a length of DNA folded. It is wound around proteins. • E.g. Animals, plants, fungi and protists.

8. Organelles • No plant or animal cells are alike but they do share some common organelles.

9. In your Notes....

10. Cell Membrane • All cells are separated from their environment by a cell membrane. • For cells with cell walls, the membrane is inside the cell wall.

11. Cell Membrane • Consists of two layers of lipids (lipid bilayer). • One lipid includes a hydrophilic (water-loving) head and hydrophobic (water-hating) tails.

12. Lipid Lipid Bi-layer Cell Membrane

13. Semi-Permeable Membrane • Proteins in the membrane allow nutrients, oxygen, and water into the cell and waste products out of the cell. • These proteins also limit other molecules from entering or leaving the cell.

14. Protein Gate Lipid Lipid

15. Cytoplasm • Cytoplasm is the semi-fluid solution found inside the cells. • It contains dissolved substances, enzymes and all other cell organelles.

16. Cytoskeleton • Scaffolding-like structure made of protein found in cytoplasm. • Helps the cell maintain or change its shape.

17. Nucleus • Usually the largest organelle the nucleus contains genetic material that directs all cell activities. • Separated from the rest of the cell by a nuclear membrane. Nucleus Pores Nuclear Membrane Nucleolus

18. Nucleus • Made up of three parts: • Nuclear envelope – a double membrane covering that controls the entry and exit of the large molecules and particles that need to go in and out.

19. Nucleus • Genetic Material – In a resting cell the DNA is unravelled (chromatin) and too small to be seen. When a cell is about to divide the DNA coils, thickens and can be seen (chromosomes).

20. Nucleus • Nucleolus – The main function of the nucleolus is the production and assembly of ribosome components (RNA, proteins).

21. Endoplasmic Reticulum (ER) • Continuous with the cell membrane and the nuclear envelope. • The ER is a series of membranes and connecting tubes that provide a work surface for chemical reactions as well as a passageway for moving materials around the cell.

22. Endoplasmic Reticulum (ER) • There are two types or ER: • Smooth ER • Rough ER (ribosomes attached)

23. Ribosomes • Found either bound to the ER or free floating within the cytoplasm. • Site where proteins are made (protein synthesis).

24. Ribosomes • Free ribosomes make proteins to be used in the cell. • The ribosomes bound to the ER make proteins to be secreted by the cell.

25. Golgi Bodies/Apparatus • A series of flattened sacs found in the cytoplasm. • The primary function is to process and package the macromolecules such as proteins and lipids that are synthesized by the cell.

26. Lysosomes • Tough, membranous bags containing digestive enzymes. • They digest excess or worn-out organelles, food particles, and engulfed viruses or bacteria.

27. Vacuoles • Vacuoles are membrane-bound compartments that can serve a variety of storage functions. • They often contain water, food or wastes.

28. Vacuoles Video • In animal cells food vacuoles engulf food where it is digested by the lysosome's enzymes. • In plants it acts as a storage, a fluid skeleton and it also hold colour and poisons. • In unicellular organisms contractile vacuoles pump water out of the cells.

29. Contractile Vacuoles • These specialized vacuoles pump excess water out of a cell and is found prominently in freshwater protists.

30. Mitochondria • Converts energy from food into a form that a cell can use, called ATP. • It is the site of aerobic respiration. A cell with a large energy requirement will have lots of mitochondria.

31. Mitochondria • It has its own circular DNA, ribosomes and transfer RNA and protein making machinery. • In the matrix the krebs cycle takes place. • The electron transport chain takes place in the cristae.

32. Cell Wall • Found in plant cells, algae and most bacteria. • Made of cellulose to provide strength and shape.

33. Chloroplasts • Found in the cytoplasm of plants. • Function is to manufacture glucose through photosynthesis. • Contains the green pigment chlorophyll.

34. Chloroplasts • Made of thylakoid discs arranged in stacks called grana.

35. Centrioles • Found in all animal cells and most unicellular organisms. • During cell division, the centriole pair extends to form spindles to move chromosomes apart.

36. Cilia and Flagella • Found in some animal cells and unicellular organisms. • Both are cellular projections and are almost identical in structure, although cilia are shorter and often more numerous. • Many cells that line surfaces within our bodies are ciliated.

37. Cilia and Flagella • Both are often associated with movement.

38. Eyes Spots • Photoreceptive organelle found in green algae and other unicellular photosynthetic organisms. • It allows the cells to sense light direction and intensity and respond to it by swimming either towards or away from the light.

39. Eye Spots • This helps the cells in finding an environment with optimal light conditions for photosynthesis. • Eyespots are the simplest and most common "eyes" found in nature.

40. Cilia and Flagella