2 Cell HistoryHooke - is the scientist who 1st coined the term “cell” – in the 1660’s he observed cork from a tree stem (they reminded him of the rooms monks lived in) Schleiden looked at plant cells & Schwann looked at animal cells. They both observed that cells make up all parts of an organism. Along with Virchow they formulated the Cell Theory.
4 The Cell TheoryIt has 3 components. 1. All living things are made of cells.2. Cells are the basic units of structure & function.3. All cells come from pre-existing cells.
5 Variety in CellsCells come in a great variety of shapes & sizes. The smallest cells are mycoplasmas & the largest cells are ostrich eggs. The size & shape of the nerve cell are related to its function. Sketch of a skin cell: Sketch of a nerve cell:
6 Cell SizeThe surface area of the cell does not increase at the same rate as the volume. Because of this, cells typically stay small & will divide rather than getting larger.
7 Differences in Cells1. Prokaryotes - have no true nucleus – DNA is not arranged into chromosomes – ex. = bacteria – they have no membrane-bound organelles.
8 2. Eukaryotes - have a nucleus - & cellular organelles.
9 Parts of the Cell1. Nucleus - control center of the cell – controls most of the activities of the cell ; also transmits hereditary information & contains DNA. The nucleus holds chromosomes (threadlike) that are seen only when the cell is dividing & chromatin (granular) when the cell isn’t dividing.
10 2. Nucleoli - these are found in the nucleus – where the assembly of ribosomes begins.
11 3. Nuclear envelope - double membrane - this surrounds the nucleus & acts as a boundary between the nucleus & the cytoplasm – it contains pores that allow substances to pass
12 4. Cell membrane - this acts as the outer boundary of the cell & contains phospholipids & proteins - it is very important because it regulates what enters & leaves the cell
13 5. Cell wall - this is found in plants, algae, fungi, & bacteria- it protects & supports the cell – it lies outside of the cell membrane & allows water & gases to pass through – plant cell walls are made of cellulose
14 6. Cytoplasm - is the jellylike layer of the cell – it contains the organelles & moves materials throughout the cell in a process called cytoplasmic streaming
15 7. Endoplasmic reticulum - this is a series of canals or channels that winds through the cytoplasm – it acts as the cell’s internal transport & connects with the nuclear envelope; there are 2 types – (1) smooth ER- this builds lipids for the plasma membrane, (2) Rough ER - has ribosomes attached - Protein synthesis
16 8. Ribosomes- the sites of protein synthesis; 2 types (1) Free - makes protein to be used in the cell, (2) Bound - make protein to be transported out of the cell
17 9. Golgi Bodies - these pinch off from the ER – they are stacks of membranes that look like tiny flattened balloons – they are areas for storage & packaging of chemicals – enzymes in this apparatus attach carbohydrates & lipids to proteins
18 10. Mitochondria - the cell’s powerhouse – they produce the energy for the cell – they have many folds on the inside called cristae that increase surface area for more energy
19 11. Plastids - are found only in plants – some store food, others have pigments – 3 types: (1) Leucoplasts - colorless – store starches in roots & stems (2) Chromoplasts - they are orange & yellow – beta carotene (3) Chloroplasts - these are green & the sites for photosynthesis
20 12. Vacuoles - bubblelike storage structures that store water, liquids, wastes, & foods – these hold plants erect & firm
21 13. Lysosomes - these are membrane-bound organelles that are formed in Golgi bodies – they are loaded with enzymes that digest large particles found in the cell – also break down old organelles
22 14. Microtubules - hollow cylinders of protein that support & shape the cell – found in the cytoskeleton, spindle fibers, centrioles, basal bodies , cilia, & flagella
23 15. Spindle fibers - appear during cell division & move chromosomes through the cytoplasm
24 16. Centrioles - small dark bodies located outside the nucleus – they are active during cell division
25 17. Cilia - short, threadlike structures used for movement – they are numerous & hairlike
26 18. Flagella - long, whiplike structures used for movement – usually only 1 per cell
27 19. Cytoskeleton - network of protein filaments that helps the cell to maintain its shape – also involved in cell movement - these are made of: a) microtubules - hollow tubes of protein – maintain cell shape & serve as “tracks” along which organelles are moved (used to make cilia & flagella) b) microfilaments - long, thin fibers that function in the movement & support of the cell – tough, flexible framework that supports the cell
28 THE CELL – PART 2CELL TRANSPORT Cells must get nutrients in & wastes out of the cell in order to stay alive. They have several methods of doing this. Some methods expend energy. Some do not. The cell membrane regulates what enters & leaves the cell & also provides protection & support. The cell membrane is a double-layered sheet called a phospholipid bilayer. The cell membrane is like a fluid-mosaic.
32 PASSIVE MECHANISMS– no cellular energy is required 1. Diffusion - molecules or ions spread from higher concentrations to lower concentrations – this continues until equilibrium is reached
33 2. Facilitated diffusion - glucose combines with a special protein carrier that helps pass it across the membrane (still from higher concentration to lower concentration)
34 3. Osmosis - water molecules diffuse from a higher to a lower concentration (water tends to diffuse toward the area of higher osmotic pressure)
35 Tonicity Drawing 1: Drawing 2: Drawing 3: Cell is _______________ Cell is _________________ Cell is ________ Solution is _______________ Solution is ________________ Solution is _____ Cell will _________________ Cell will __________________ Cell will ______
36 4. Filtration - molecules are forced through membranes by the hydrostatic pressure that is greater on one side of the membrane than on the other (this usually happens with blood vessels)
37 ACTIVE MECHANISMS – cellular energy is required 1. Active transport - using carrier proteins to move substances from lower concentrations to higher concentrations (sugars, a.a.’s, ions)
38 2. Endocytosis - molecules that are too large to enter a cell by diffusion enter by the formation of a vesicle - 2 Types: a) phagocytosis - “cellular eating” – takes in solids (common in white blood cells) b) pinocytosis - “cellular drinking ” – takes in liquids (water)
40 3. Exocytosis - sends materials out of the cell
41 Organisms with only one cell are called unicellular while organisms with many cells are called multicellular.
42 LEVELS OF ORGANIZATION 1. Cells - basic functional unit of life 2. Tissues - group of similar cells that perform a particular function 3. Organs - groups of tissues working together 4. Systems - group of organs working together (11 in the body)