Presentation is loading. Please wait.

Presentation is loading. Please wait.

CELLS: The Building Blocks of Life. History of the Cell Robert Hooke is a scientist from England. He experimented with clocks, telescopes and microscopes.

Similar presentations


Presentation on theme: "CELLS: The Building Blocks of Life. History of the Cell Robert Hooke is a scientist from England. He experimented with clocks, telescopes and microscopes."— Presentation transcript:

1 CELLS: The Building Blocks of Life

2 History of the Cell Robert Hooke is a scientist from England. He experimented with clocks, telescopes and microscopes. He became famous for the observation of thin slices of bark through the microscope in It was this observation that led him to….THE DISCOVERY OF THE CELL !

3 How did he discover the Cell? 1.He sharpened his knife as keen as a razor blade. 2.He cut off a very thin piece of cork with his knife. 3.He placed the thin piece of cork on a black object plate. 4.Through the microscope, he observed that the cork cells were perforated and porous, much like a honeycomb.

4 CORK CELLS

5 Microscopes Light microscope can magnify objects up to 1000 x Thus, many organelles cannot be seen clearly Electron microscope can magnify objects up to > x Thus, many organelles can be seen more clearly

6 Micrographs What is it? A camera can be fitted to a microscope to take pictures. This picture is called the micrograph.

7 Micrographs Photomicrograph Taken using a light microscope Pictures are in colour Electronmicrograph Taken using an electron microscope Pictures are in black- and-white but images can be artificially colourised.

8 What does a cell consist of?

9 cytoplasm nucleus cell wall What does a cell consist of?

10 Protoplasm -Nucleus + Cell surface membrane + Cytoplasm Organelles - Specialised structures within the cell

11 Parts of a Cell The protoplasm of a cell is made up of three parts: Cell surface membrane Surrounds the cytoplasm Partially permeable Hence controls substances entering or leaving the cell Nucleus Consists of nucleoplasm, nuclear envelope, one or more nucleoli and chromatin Functions: controls cell activities (e.g. cell growth and repair of worn out parts) ; ;essential for cell division. Cells without nucleus cannot divide and have short lifespans. Cytoplasm Protoplasm between the cell surface membrane and nucleus Where most cell activities occur Contains enzymes and specialised structures (organelles) nucleoplasm nucleolus chromatinnuclear envelope

12 Cell surface membrane (plasma membrane) Cell surface membrane Animal cell Plant cell

13 Cell surface membrane Photomicrograph Cheek cell Onion epithelial cell Cell surface membrane (plasma membrane)

14 Cell wall Non-living cell wall made of cellulose that encloses the entire plant cell, surrounding the cell membrane. The cell wall is fully permeable and is absent in animal cells. Function: It protects the cell from injury and gives the plant cell a fixed shape.

15 What does a cell consist of? Cell wall Only exist in plant cells Absent in animal cells

16 What does a cell consist of? Cell wall Photomicrograph

17 Parts of a Cell The protoplasm of a cell is made up of three parts: Cell surface membrane Surrounds the cytoplasm Partially permeable Hence controls substances entering or leaving the cell Nucleus Consists of nucleoplasm, nuclear envelope, one or more nucleoli and chromatin Functions: controls cell activities (e.g. cell growth and repair of worn out parts) ; ;essential for cell division. Cells without nucleus cannot divide and have short lifespans. Cytoplasm Protoplasm between the cell surface membrane and nucleus Where most cell activities occur Contains enzymes and specialised structures (organelles) nucleoplasm nucleolus chromatinnuclear envelope

18 Cytoplasm

19 Cheek cell Drawing of Onion epithelial cell

20 Parts of a Cell The protoplasm of a cell is made up of three parts: Cell surface membrane Surrounds the cytoplasm Partially permeable Hence controls substances entering or leaving the cell Nucleus Consists of nucleoplasm, nuclear envelope, one or more nucleoli and chromatin Functions: controls cell activities (e.g. cell growth and repair of worn out parts) ; ;essential for cell division. Cells without nucleus cannot divide and have short lifespans. Cytoplasm Protoplasm between the cell surface membrane and nucleus Where most cell activities occur Contains enzymes and specialised structures (organelles) nucleoplasm nucleolus chromatinnuclear envelope

21 Nucleus

22 Nucleus- what is inside? Chromatin -A network of thread-like structures in the nucleus -It controls the activities of the cell, such as cell division -Each chromatin is made up of proteins and deoxyribonucleic acid (DNA) DNA contains:  -Hereditary information  -Instructions that a cell needs for carrying out all chemical reactions within itself.

23 Nucleus- what is inside? Chromosome - When the cell is dividing, chromatin condenses and becomes highly coiled structures called chromosomes (which appear as thick, rod-shaped structures under light microscope) chromosome

24 The Nucleus Nucleus

25 The nucleus Nucleus Cheek cell Onion epithelial cell

26 Vacuole - Fluid-filled space enclosed by a membrane -Contained in the cytoplasm Function: -Storage of substances within the cell

27 Vacuole AnimalPlant Size and number Small and many Large and only one Contents Water; food substances Cell sap (contains dissolved substances such as sugars, mineral salts and amino acids, enclosed by a membrane called tonoplast) How long do they exist? TemporarilyMore permanent

28 Vacuole

29

30 Chloroplast -Oval structures found in plant cells -Found in the cytoplasm Function: -Contains the green pigment chlorophyll, which is essential for plants to make food (the process of photosynthesis)

31 The chloroplast Chloroplast Only exist in plant cells Absent in animal cells

32 Chloroplast Chloroplasts Photomicrograph

33 Chloroplast Electronmicrograph

34 Mitochondria (sin: Mitochondrion) -Small, sausage-shaped -Can be seen clearly under electron microscope Function:  - Aerobic respiration occurs in the mitochondria  -Aerobic respiration is the process whereby food substances are oxidised to give energy the cell needs to carry out activities like growth and reproduction

35 Mitochondria Electronmicrograph of mitochondrion

36 Mitochondria Electron- micrograph:

37 Mitochondria Electron- micrograph: (b) A plant cell

38 Mitochondria Electronmicrograph:

39 Ribosome Small, round structures Either attached to certain membranes in the cells or lie freely in the cytoplasm. Function:  Synthesize proteins in the cell

40 Ribosomes Electron- micrograph:

41 In summary- Most cells share certain features: C ytoplasm Protoplasm N ucleus C ell surface membrane Nucleoli- Building proteins Nucleoplasm- small round mass of protoplasm called the nucleoplasm Nuclear envelope- Separates nuclear content from the surrounding Cytoplasm Chromatin threads- Found in nucleoplasm, contain hereditary materials which condense to form chromosomes Partially permeable membrane covering of cell Controls substances entering and leaving cell Gel-like substance forming major part of cell Site where most organelles are found: Mitochondria (sausage shaped) -for cell respiration Centrioles - involved in cell division Chloroplasts - Contains chlorophyll, green pigment needed for photosynthesis Vacuoles - fluid-filled storage sacs Ribosomes- Synthesise proteins

42 Cell seen under electron microscope

43

44 Rough endoplasmic reticulum Rough endoplasmic reticulum (RER) has a surface that appears rough because of small particles called ribosomes that are attached to its outer surface. The outer surface of the RER is continuous with the nuclear envelope. Ribosomes are small round structures that are either attached to the membrane of the RER or lie freely in the cytoplasm. They are needed to synthesise proteins. The ribosomes attached to the RER make proteins that are usually transported out of the cell The ribosomes lying freely in the cytoplasm make proteins that are used within the cytoplasm of that cell. The RER transports proteins made to the Golgi apparatus for secretion out of the cell.

45 Smooth endoplasmic reticulum The smooth ER (SER) does not have ribosomes attached to its membrane. SER is more tubular that than the RER. It is connected to the RER. The SER synthesises fats and steroids and converts harmful substances into harmless materials.

46 Golgi apparatus Golgi apparatus or Golgi body is shaped like a disc. It consists of a stack of flattened spaces surrounded by membranes. Vesicles or tiny spherical spaces enclosed by a membrane can be seen fusing with one side of the Golgi apparatus and pinching off from the opposite side. The Golgi apparatus stores and modifies substances made by the ER and packages these substances in vesicles for secretion out of the cell.

47 Plant and animal cells: Similarities Both have nuclei Both have cell membranes Both have cytoplasm Both have mitochondria, ribosomes, ER, Golgi apparatus, vesicles

48 Plant and animal cells: Differences Animal cellPlant cell Many small vacuoles No chloroplasts No cell wall centrioles present No regular shape A large central vacuole Chloroplasts present Cellulose cell wall No centrioles Regular shape

49 Differentiation Growth in an organism involves cell division. New cells produced may change and develop into new tissues. This process by which a cell becomes specialised for a specific function is called differentiation. Cells may develop special structures or lose certain structures for them to carry out specific functions. e.g. Human cells become differentiated to form various types of cells: liver cells, muscle cells, sperm cells, epithelial cells, blood cells, etc e.g. Plant cells differentiate to form xylem cells, phloem cells, etc

50 Root Hair Cell FunctionsAdaptations Absorption of water & mineral salts from soil Long and narrow to increase the surface area: volume ratio, thus water and mineral salts can be efficiently absorbed from the soil.

51 Surface Area to Volume Ratio CubeSurface area/cm 2 Volume/cm 3 Surface area: volume Side 1 cm Side 2 cm Side 3 cm 6 cm 2 24 cm 2 54 cm 2 8 cm 3 1 cm 3 27 cm 3 2:1 3:1 6:1

52 Xylem Vessels FunctionsAdaptations To provide support for stem & leaves Lignin deposited on wall To conduct water & salts from roots to leaves Long & thin tubes, no cross walls or protoplasm which enables water to move easily through the lumen (central space)

53 Red Blood Cells FunctionsAdaptations To carry oxygen around the body -Circular biconcave, increases the SA to Vol. ratio. -no nucleus, enabling it to contain more haemoglobin

54 A group of cells work together to form a tissue. intestinal epithelium (tissue) made up of intestinal epithelial cells epithelium in the trachea (tissue) made up of epithelial cells and gland cells cartilage in the trachea (tissue) made up of connective tissue cells epithelium in the lungs (tissue) made up of epithelial cells connective tissue in the lungs made up of connective tissue cells muscle cell neurones intestinal epithelial cell epithelial cell gland cell muscle tissue made up of muscle cells nervous tissue made up of neurones (nerve cells) connective tissue cell epithelial cell Tissues

55 Tissue A group of similar cells which work together to perform a specific function -Cells of the same type form simple tissue E.g. epidermis tissue (plants) and epithelial tissues (animals) -Cells of different types form complex tissue E.g. connective tissue (animals), blood, vascular tissue (plants)

56 Different tissues combine to form an organ. trachea (organ) lungs (organs) stomach (organ) intestine (organ) muscle tissue cartilage (tissue) muscle tissue connective tissue nervous tissue intestinal epithelium (tissue) epithelium (tissue) Organs

57 Several organs work together to make up an organ system. lungs (organs) trachea (organ) intestine (organ) stomach (organ) digestive system (organ system) respiratory system (organ system) Systems

58 human (organism) digestive system (organ system) respiratory system (organ system) Various organ systems work together to make up an organism. Specialised Cells, Tissues, Organs & Systems

59 controls cell activities Protoplasm Cell surface membrane Tissues CELL Organs Cellulose cell wall (found only in plants) made up of consists of which NucleusCytoplasm and contains Chromatin (made up of DNA) Organism Organ systems is the partially permeable, outer covering enclosing the cytoplasm surrounds the nucleus and is where most cell activities occur Chloroplasts (in plant cells) Mitochondria (sites of energy release) contains organelles Vacuoles (contain water and food substances) Ribosomes (involved in protein synthesis)

60 You should be able to: Know the functions and identify from diagram and photomicrographs, the nucleus, chloroplast, ribosome, mitochondrion, endoplasmic reticulum. Examine under the microscope an animal cell (from fresh liver& human check cell) and a plant cell (from Hydrilla & onion ) Compare and contrast the structures of plant and animal cell Relate the adaptations of a cell structure to its functions for the following: Absorption-root hair cells/ Conduction and support- xylem vessels /Transport of oxygen-red blood cells Differentiate between the terms cell, tissues, organ and organ system.


Download ppt "CELLS: The Building Blocks of Life. History of the Cell Robert Hooke is a scientist from England. He experimented with clocks, telescopes and microscopes."

Similar presentations


Ads by Google