Cambridge IGCSE Biology

1. Cells and tissues

BiologyEdexcel international GCSE

Human Biology

1- cells and tissues

a) Recognise cell structures as seen with a light microscope and with an electron microscope.

Describe the functions of cell structures including

1- the nucleus, 2- cytoplasm, 3- cell membrane,4- mitochondria, 5- endoplasmic reticulum, 6- ribosomes.

1- cells and tissues Under an electron microscope parts of the animal cell such as the ribosomes, Endoplasmic reticulum mitochondria can be seen. The main differences between a plant cell and an animal one is the lack of certain organelles suchas a permanent vacuole, cell wall and chloroplasts.

Apart from this plant cells also have a more regular structure.

1- cells and tissues The Functions of the parts of the cell:1- Nucleus: contains chromosomes (46 in humans) which carry the genetic information. It controls the activity of the cell by controlling which proteins the cell will synthesis. 2- Cytoplasm: this is where chemical reactions take place .

3- Cell membrane: this controls what substances can pass in and out of the cell. It is selectively permeable.

1- cells and tissues The Functions of the parts of the cell:

4- Mitochondria : this carries out some of the reactions in respiration.Cell membrane: this controls what substances can pass in and out 5-Endoplasmic reticulum: an essential component in the synthesis and transport of protein. It is anetwork of membranes.. It is selectively

Ribosomes: some endoplasmic reticulum are covered with minute granules 6-Ribosomes: some endoplasmic reticulum are covered with minute granules called ribosomes. These build and assemble proteins according to instructions from mRNA.

1- cells and tissues b) Describe a DNA molecule as two strands coiled to form a double helix, the strands being linked by a series of paired bases: adenine (A) with thymine (T), and cytosine (C) with guanine (G). according to instructions from mRNA.

1- cells and tissues DNA or deoxyribonucleic acid contains two strands of alternating sugar and phosphate groupscoiled to form a double helix.

The strands are linked by two nitrogen bases at each "rung". There are four different bases: Adenine(A), Thymine(T), Cytosine(C), and Guanine(G). In DNA the bases are always paired. So if on one strand the base is A, the other must be T and likewise if on one strand it is C then on the other it must be G..

c) Understand the multiplication of cells with a simple outline description of the four stages ofmitosis. Understand that division of a diploid cell by mitosis produces two cells that contain identical sets of chromosomes. Understand that mitosis occurs during growth, repair , cloning and asexual reproduction.

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Mitosis:Mitosis is a process of separating a cell into two with identical sets of chromosomes. This occursduring growth, repair, cloning and asexual reproduction.1. Prophase - the cell duplicates its DNA.2. Metaphase - the centrioles (duplicated DNA) align themselves along the equator (middle) and send out tubules that connects to the centromere and connects the two strands of chromosomes (condensed DNA).3. Anaphase - half of the chromosomes are pulled one way and vice versa.4. Telophase - cell membranes closes in and splits the cell..

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What happens during mitosis?

d) Understand the grouping of cells into tissues:1- bone, 2- muscle (voluntary, involuntary and cardiac),3- blood, 4- nervous tissue5- epithelium (squamous ( scale like ) and ciliated, with reference to cells lining the cheek and trachea).

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e) Recall the organization of cells into organs.

There are many types of tissues:1.Bones are collection of cells that secrete calcium salts.2. Muscle these can be voluntary, involuntary or also cardiac

1- cells and tissues

3. Blood collection of red and white blood cells.4. Nervous tissue makes up the brain, nerves and spinal cord.

5. Epithelium these are tissues that line organs. They can be both squamous or ciliated.

There are many types of tissues:1.Bones are collection of cells that secrete calcium salts.2. Muscle these can be voluntary, involuntary or also cardiac

1- cells and tissues

3. Blood collection of red and white blood cells.4. Nervous tissue makes up the brain, nerves and spinal cord.

5. Epithelium these are tissues that line organs. They can be both squamous or ciliated.

1- Tissues that perform the same function are grouped together to form organs. e.g. Heart.

2- Organs that perform the same function are grouped together to form organ systems. e.g. The circulation system3- Organ systems are grouped together to form organisms. e.g. Humans.

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1- Tissues that perform the same function are grouped together to form organs. e.g. Heart.

2- Organs that perform the same function are grouped together to form organ systems. e.g. The circulation system3- Organ systems are grouped together to form organisms. e.g. Humans.

1- cells and tissues

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Bonds between Water molecules are hydrogen bonds Because of the Hydrogen bond weakness the water molecules attract to any charged molecules more than water molecules themselves

1 life style, health and risk Water is powerful solvent for polar substances

Ionic compounds are polar substance such as Sodium chloride ( NaCl )

Carbon containing molecule ( organic )with ionised groups ( carboxyl –COO , Amino group –NH2)Can be soluble in water ( glucose one of them)Because it contains hydroxyl group –OH Then glucose called solute and water called solvent

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3- Distinguish between A-monosaccharides, B-disaccharidesC-polysaccharides(glycogen and starch )( amylose and amylopectin) relate their structures to their roles in providing and storing energy ( ß-glucose and cellulose are not required in this topic).

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Monosaccharide ( simple sugar ) 1- they are the smallest molecule of carbohydrates 2-they are soluble in water and test sweet

3- glucose the most important monosaccharide -All green leaves produce glucose in photosynthesis- our bodies transport glucose in the blood - all cells use glucose in respiration as energy source -Glucose used as building block for many large molecule

1 life style, health and risk Glucose structure Molecular formula C6H12O6 We can write this formula on paper as linear but it can not exist in linear form Because each carbon arranges its four bonds into TETRAHEDRON

So oxygen attaches carbon atom number 5 , 1

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Other monosaccharide important in our cells Fructose and galactose are example of hexose

Other monosaccharide important in our cells Such as ribose / deoxyribose which are components of NUCLIC ACIDS ( DNA / RNA )

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4- Describe how monosaccharides join to form disaccharides (sucrose, lactose and maltose) and polysaccharides (glycogen and amylose)through condensation reactions forming glycosidic bonds, and how thesecan be split through hydrolysis reactions.

1 life style, health and risk Disaccharidesare carbohydrates made of 2 monosaccharides

Condensation is the chemical reaction name to form disaccharide with glycosidic bond

Hydrolysis is the chemical reaction name to add water molecule to break down the glycosidic bond

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Examples of disaccharides Maltose made by condensation reaction of 2 glucose molecules

Lactose made by condensation reaction of one galactose molecule and one glucose molecule

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3- Distinguish between A-monosaccharides, B-disaccharidesC-polysaccharides(glycogen and starch )( amylose and amylopectin) relate their structures to their roles in providing and storing energy ( ß-glucose and cellulose are not required in this topic).

1 life style, health and risk Such as disaccharides , polysaccharides are made of many MONOSACCHARIDE molecules linked together by GLYCOSIDIC bond

Monomer changes into polymer

Starch and glycogen are poly saccharides and their function is storing energy

1 life style, health and risk Starch is a mixture of 2 poly saccharides Amylose molecule is unbranched chain from α glucose Amylopectin molecule is branched chain

1 life style, health and risk Glycogen is a polymer made of α glucose similar to Amylopectin molecule is branched chain

Glycogen is found in liver cells and muscles fibers as source of energy

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Starch test

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Describe the synthesis of a triglyceride by the formation of ester bonds during condensation reactions between glycerol and three fatty acids andrecognise differences between saturated and unsaturated lipids.

Lipids can be found in animal as fats while it is oils in plants

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In room temperature Fats are solid oils are liquids

Number of Oxygen atoms are less than in carbohydratesLipids are hydrophobic ( could not dissolve in water ) They are dissolved in organic solvents such as ALCOHOL

Fats and oils are compound called triglyceride

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Triglyceride is formed by condensation reaction Glycerol and fatty acid

Fats and oils are compound called triglyceride

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Triglyceride classified as two types Saturated ( fats ) with single bond in carbon chain

Unsaturated (oils ) with at least one double bond in carbon chain which are called ( monounsaturated lipids)while oils with more than one double bond are called (Polyunsaturated lipids )