T HE C ELL C H A P T E R 1 P G. 4-23

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1 T HE C ELL C H A P T E R 1 P G. 4-23

2 A CELL IS THE SMALLEST LIVING UNIT KNOWN. IT IS OFTEN CALLED THE BUILDING BLOCK OF THE BODY, AND IS THE BASIC STRUCTURAL AND FUNCTIONAL UNIT OF AN ORGANISM.

3 CELL THEORY In 1838 the scientists Matthias Schleinden and Theodor Schwann discussed their knowledge of cells and came up with the Cell Theory All living things consist of one or more organised structures that are called cells Cells are the basic functional unit of life New cells are produced from existing cells

4 CELLS Unicellular organisms: simple organisms such as bacteria & yeasts. Multicellular organisms: complex organisms such as plants & animals. In multicellular organisms cells of one kind are organized into tissues & the tissues are organised into organs.

5 TYPES OF CELLS Cells can be found in many shapes and sizes depending on where they are located and the job they do. Simple cells, known as prokaryotic cells pro meaning before and karyote meaning nucleus Complex cells, known as eukaryotic cells eu meaning true and karyote meaning nucleus

6 A simple cell Lacks a membrane bound nucleus meaning genetic material is spread throughout the cell They can be bacteria or archaea They have flagella and pili on the outside that helps them move Some have a wall layer like a capsule, but generally they have cell wall and plasma membrane PROKARYOTE

7 COMMON PROKARYOTIC SHAPES

8 EUKARYOTE Much bigger in size and volume than a prokaryote Has membrane bound compartments- organelles, for specific metabolic function Has a membrane bound nucleus with DNA Can have a complex cilia or flagella for movement Animal cell and plant cells are eukaryotic

9 WHICH IS WHICH??

10 THE CELL IS THE BASIC UNIT OF LIFE A cell is completely contained within a plasma membrane (or cell membrane). This membrane keeps all of the cell's contents neatly inside, while keeping out harmful substances. Inside the cell are the cytoplasm, the nucleus, and the organelles. The cytoplasm is a gel-like substance in which the nucleus and organelles are found. The nucleus is the brain of the cell. It contains the genetic information in the form of chromosomes, as well as the nucleolus, a structure that helps the nucleus function. The nucleus is completely separated from the rest of the cell by a membrane similar to the plasma membrane that encircles the cell.

11 THE HUMAN CELL! The human body is made up of trillions and trillions of cells. This is because cells make up everything in the body. There are bone cells, and blood cells, and heart cells, and skin cells, and hair cells, and brain cells, and so many, many more. Each of these cells functions a bit differently, but their overall purpose is to keep the body functioning, growing, and developing properly. Each cell also has its own particular structure, but there are some general characteristics that are found in most cells.

12 ORGANELLES: The human body contains many different organs, such as the heart, lung, and kidney, with each organ performing a different function. Cells also have a set of "little organs," called organelles, that are adapted or specialised for carrying out one or more vital functions. Each of the organelles has a different function, but they all work to keep the cell healthy and help it perform its job. Some common organelles can be found on the next slide.

14 NUCLEUS This is the defining structure of eukaryotic cells and is enclosed within a double membrane known as the nuclear envelope. This is the control centre of the cell. The nucleus contains stained material known as chromatin that are made of DNA. NUCLEOLUS This is found inside the nucleus and manufactures ribosomes.

CYTOPLASM/CYTOSOL Cytoplasm: The contents of a cell other than the nucleus. It includes the cytosol (molecules in a gel like solution) and the cell organelles.

15 CYTOPLASM/CYTOSOL Cytoplasm: The contents of a cell other than the nucleus. It includes the cytosol (molecules in a gel like solution) and the cell organelles. Cytosol: The soluble, gel-like part of cytoplasm. CYTOSKELETON This is made up of protein filaments and tubules that support the cell and determine cell shape. It also allows chromosomes to move during cell division.

PLASMA MEMBRANE This is an active boundary that

permeable as it only allows some substances to cross

16 PLASMA MEMBRANE This is an active boundary that separates the internal cellular environment from the external cellular environment. It is said to be semipermeable or selectively permeable as it only allows some substances to cross it in or out. VESICLES These are membrane bound sac s that move substances into and out of cells.

17 RIBOSOMES For the purposes of genetics, the most important organelles are the ribosomes. Ribosomes synthesise amino acids into proteins. Ribosomes can be found freefloating in the cytoplasm, or attached to an organelle called the endoplasmic reticulum (ER). MITOCHONDRIA Mitochondria are found in the cytoplasm and are the sites of cellular respiration. Energy can be released to form ATP molecules which is used by the cell to power cellular processes

Transports the molecules that need to get to a specific destination intracellular transport system Rough ER is studded with ribosomes Smooth

18 ENDOPLASMIC RETICULUM (ER) Micrograph of rough endoplasmic reticulum network around the nucleus (shown in lower right-hand side of the picture). Dark small circles in the network are mitochondria. Transports the molecules that need to get to a specific destination intracellular transport system Rough ER is studded with ribosomes Smooth ER, has no ribosomes attached, but stores Ca 2+ ions GOLGI APPARATUS Process and package the molecules that are synthesised by the cell e.g. digestive enzymes that are discharged to the intestines. Also known as the golgi body

19 VACUOLES Store sugar, minerals, proteins and extra water Liquid filled spaces surrounded by a membrane LYSOSOMES Digest worn out cells. They get rid of waste, food and bacteria by engulfing them and breaking them down with digestive enzymes lysis to break apart

The green colour of these organelles is due to the presence of light-trapping

20 CENTRIOLES These produce microtubules for cell division CHLOROPLASTS This is the site of photosynthesis in plants. The green colour of these organelles is due to the presence of light-trapping pigments known as chlorophylls. Chloroplasts are only present in the cells of the plant that are exposed to sunlight.

22 FILL IN THE ORGANELLES.

23 CHECK THE ANSWERS (1) Nucleolus (2) nucleus (3) ribosome (4) vesicle (5) rough endoplasmic reticulum (6) Golgi apparatus (7) Cytoskeleton (8) smooth endoplasmic reticulum (9) mitochondria (10) vacuole (11) cytoplasm (12) lysosome (13) centrioles in centrosome

24 ANIMAL CELL Can be in a variety of shapes There are many different specialised animal cellsin the human body there are 210 different cell types (skin, bone, organs etc) Contain all the organelles and plasma membrane around the cell as mentioned before Has only a small vacuole

25 PLANT CELL Has a cell wall. It is a rigid layer outside the cell membrane that provides structure, protection and filtering Has a large central vacuolekeeps the cell plumped up (turgor) Has chloroplasts which contain chlorophyll to give plants the green colour Cell wall and Chloroplast

26 WHICH IS WHICH?

27 S U R FA C E A R E A T O V O L U M E R AT I O S

28 SURFACE AREA TO VOLUME RATIOS. In order to survive cells must: Allow substances to enter them Allow substances to leave them The size of the surface area exposed to surrounding environment determines the quantity of substances that enter and leave the cell.

29 SURFACE AREA TO VOLUME RATIOS. The surface-area-to-volume ratio (variously denoted sa/vol or SA:V), is the amount of surface area per volume of an object or collection of objects.

30 CALCULATING SURFACE AREA AND VOLUME Surface Area This is the area of a surface. (length x width of the surface) x the number of surfaces Volume Length x width x height of object

31 SURFACE AREA TO VOLUME RATIOS. The surface area of the cell is dependent on the size and shape of the cell. A cell with a total surface area of 200 mm 2 and a volume of 100 mm 3 has a surface area : volume of 200mm 100mm = 2 : 1 = 2

32 OBJECT SURFACE AREA VOLUME SA:V Cube 1 Cube 2 Cuboid

34 The bigger the number, the better! More movement in/out of the membrane is allowed!!

35 HOW DOES IT RELATE TO BIOLOGY? An increased surface area to volume ratio also means increased exposure to the environment. E.g. The many tentacles of jellyfish increased surface area for the acquisition of food. Greater surface area allows more of the surrounding water to be sifted for nutrients.

36 The numerous internal branching of the lung increases the surface area through which oxygen is passed into the blood and carbon dioxide is released from the blood.

37 The intestine has a finely wrinkled internal surface, increasing the area through which nutrients are absorbed by the body. The small intestines have about the same surface area as a tennis court!

38 SURFACE AREA TO VOLUME RATIOS. As the size of a cell (volume) increases, the SA: V decreases. Therefore the larger cell could lose or gain less substances over time than a smaller cell. Large internal volume relative to surface area makes it more difficult to traffic materials into and out of the cell The more surface area the cell has, the more area there is to exchange materials with the outside environment. Which shape of cell has the most efficient surface area: volume for the transfer of materials across a membrane?

CELL PART Expanded Definition Cell Structure Illustration Function Summary Location ALL CELLS DNA Common in Animals Uncommon in Plants Lysosome

CELL PART Expanded Definition Cell Structure Illustration Function Summary Location is the material that contains the Carry genetic ALL CELLS information that determines material inherited characteristics.