CELL STRUCTURAL AND FUNCTIONAL UNIT
cell is the basic structural and functional unit of life. |
cell -> tissue -> organ -> organ system -> organism (this is how cell is the structural unit) |
cell does metabolic functions, produces glucose, energy(in the form of ATP[adenine triphosphate]) |
CELL SIZES AND SHAPES
smallest cell: mitoplasm(0.3 micrometer) |
longest cell: neuron |
largest cell: ostrich egg |
CELLS IN ANIMALS |
smallest cell in males: sperm |
largest cell in males: WBC |
smallest cell in females: RBC |
largest cell in females: ovum |
PLASTIDS
1) double membrane structure. |
2) present mainly in plant cells and euglena(animal cell) |
3) has its own circular DNA |
4) ribosomes present are 70s |
5) plastids generally have pigments which give them colour |
- types of plastids - |
1) leucoplasts: colourless, no pigment. functions: storage of starch(potato), proteins(pulses), oil(peanuts) |
2) chromoplasts: coloured due to pigment. functions: to attract pollinators, nutritional value. |
3) chloroplasts: green coloured due to chlorophyll. functions: photosynthesis. |
LYSOSOME
1) single membrane structure. |
2) also called suicidal bag. |
3) membrane bound organelle having digestive enzymes. |
4) absent in matured RBC and prokaryotic cells. |
- FUNCTIONS - |
1) cleans the cell by destroying worn out organelles. |
2) destroys pathogens and toxic materials entering the cell. |
3) they carry out autophagy -> destroying its own cell. |
-steps of autophagy- |
when a cell is damaged or infected -> lysosome enzymes gets activated -> lysosomes burst and digestive enzymes are released inside the cell -> the cell is digested completely. |
DIFFUSION AND OSMOSIS
DIFFUSION |
OSMOSIS |
1) movement of substances from high concentration to low concentration. |
1) diffusion through semi-permeable membrane. |
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2) movement of substances from an area of higher concentration to an area of lower concentration through a semi-permeable membrane. |
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-applications and importance of osmosis- |
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1. absorption of water by root hair. |
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2. unicellular organisms gain water through osmosis. |
NUCLEUS
Control center of the cell. |
common stain used for nucleus: acetocarmine |
exceptions for nucleus: matured RBC of mammals, Platelets, Sieve tubes of phloem. |
Covered by two membranes-> inner and outer membrane(together they are called the nuclear membrane) |
ER is an extension of the outer membrane. |
Nuclear membrane has openings called nuclear pores which contain Amuli. |
Nuclear pore with amuli is called pore complex. |
Nuclear pores allow passage of selective materials in and out of the nucleus. |
nucleus contains a dense part called the nucleolus. |
ribosomal subunits of rRNA are formed in the nucleus. |
nucleolus is also important for protein synthesis. |
nucleus is filled with jelly like substance called nucleoplasm/ karyoplasm/ nuclear sap. It contains all the components of the nucleus like nucleolus, chromatin fibres, enzymes, and nucleotids. |
the nuclear membrane seperates nucleoplasm from cytoplasm. |
nucleus contains thread like structures called chromatin. chromatin condenses during cell division to form chromosomes. chromosomes are strands of DNA wrapped around proteins called histones. |
chromosomes contain genes that contain codes for protein synthesis. |
ENDOMEMBRANE SYSTEM
1) organelles work together to make the cells work efficiently and properly |
2) organelles who work together form this system. (functions of organelles depend on eachother) |
3) organelles: ER, golgi body, lysosomes, vacuoles, etc. |
CELL DIVISION
the process in which a cell divides to form two or four daughter cells. |
cells which do not divide: RBC, WBC, Platelets, Neurons, Sieve cells. |
- why is cell division important- |
1. growth of organism. |
2. to repair damaged tissue of the body. |
3. to recover from injuries. |
4. for production of gametes that help in reproduction. |
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DNA(DEOXYRIBOSE NUCLEIC ACID)
1) The universally accepted model of DNA is the double helical structure proposed by WATSON AND CRICKE. |
2) adenine = thymine |
3_ cytosine ≡ guanine |
4. the functional unit of chromosomes are genes. Genes contain the code for production of proteins and is made of 3 alphabets . |
5. DNA contains all the information necessary for the growth and development of the organism. |
MITOCHONDRIA
1) powerhouse of the cell. |
2) absent in matured RBC's, prokaryotic cell. |
3) it produces energy in the form of ATP during cellular respiration. |
4) stain used under microscope: Janus Green. |
5) double membraned organelle. |
6) semi autonomous organelle( does a few functions by itself) |
-why is mitochondria a semi autonomous organelle?- |
1) it has DNA and Ribosomes |
2) it can sustain for 10 to 12 hours without the nucleus |
3) it depends on the nucleus for some proteins. |
4) it can produce certain proteins required for its metabolism. |
GOLGI BODY
1) modifying and packaging unit. |
2) absent in prokaryotic cells, matured sperms and matured RBC's. |
3) consists of membrane bound sac-like structures called cisternaes, secretory vesicles. |
4) single membrane structure. |
5) it produces complex sugars from simple sugars. |
6) it packs substances in secretory vesicles. |
7) it gives rise to lysosomes. |
8) it is a site for formation of glyco-lipids and glyco-proteins. |
PLASMA MEMBRANE
1) made of lipids and proteins and some carbohydrates. |
2) structure: sea of lipids in which proteins are present(phospho lipid bylayers) |
3) plasma membrane is a semi permeable/selectively permeable membrane. |
4) it allows certain substances to pass through it. |
- functions of plasma membrane - |
1) movement of substances in and out of the cell. Higher concentration to lower concentration where ATP is not used. |
ENDOPLASMIC RETICULUM
1) found in all plant and animal cells. |
2) absent in mature RBC in mammals and prokaryotic cells. |
3) gives rigid support to cells. |
-ELEMENTS OF ER- |
1) cisternae(RER): flat structures. |
2) vesicles(SER): round and smooth. |
3) tibules(SER): tube like structures. |
- FUNCTIONS OF ER - |
1) helps in the transfer of materials between various regions of the cytoplasm and between the nucleus and the cytoplasm. |
2) RER helps in protein synthesis. |
3) SER helps in lipid(fat) synthesis. |
4) Biogenesis: process of producing lipids and proteins and using them to produce membranes of cells is called Biogenesis. |
5) SER detoxifies drugs and poisons in the cell. |
CHROMOSOMES
diploid: two sets of chromosomes, only in vegetative cells. |
haploid/gametal cells: only one set of chromosomes. |
chromosomes contain all the information required for growth and development of an organism.
TYPES OF SOLUTIONS
- ISOTONIC SOLUTION(balanced) - |
- HYPOTONIC SOLUTION (diluted)- |
- HYPERTONIC SOLUTION(concentrated) - |
1. it has exactly the same water concentration as the cell. |
1. it has more concentration of water than the cell. |
1. it has less concentration of water than the cell. |
2. so there is no net water movement across the cell. |
2. water moves in the cell and causes the cell to swell. |
2. water moves out of the cell and causes the cell to shrink. |
DIFFERENCES BETWEEN PROKARYOTES AND EUKARYOTES
PROKARYOTES |
EUKARYOTES |
1. prokaryotes have a nucleoid and nuclear membrane is absent. |
1. has a well defined nucleus with nuclear membrane. |
2. lacks membrane bound organelles. |
2. membrane bound organelles are present. |
3. DNA is circular. |
3. DNA is linear. |
4. ribosomes are small(70s) |
4. ribosomes are large(80s) |
5. single chromosomes are present. |
5. multiple chromosomes are present. |
6. cell wall is peptidoglycan. |
6. cell wall is cellulose(plants) and chitin(animals) |
HISTORY OF CELL
robert hooke: discovered cork cell(which was dead) using a primitive microscope. |
anton von leeuwenhoek; found free living cells in pond water using an improved microscope. |
robert brown: discovered nucleus |
purkinje: coined the term protoplasm. |
schleiden and schwann: made the cell theory. |
rudolph virchow: cell theory. |
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SOME TERMS
homologous chromosomes : chromosomes which are similar in structure and function. |
crossing over: process of exchange of genetic material between non-sister chromatids of homologous chromosomes. |
CENTROSOMES
1) present only in animal cells. |
2) form spindle fibres during cell division. |
TRANSPORTATION IN THE CELL
PASSIVE TRANSPORTATION |
ACTIVE TRANSPORTATION |
1. high concentration to low concentration. |
1. low to high concentration. |
2) no energy is used. |
2. energy used. |
3) eg: diffusion, osmosis. |
3. eg: reabsorption of substances in the kidney, sodium/potassium pump. |
RIBOSOMES
1) found on the surface of ER. |
2) freely found in the cytoplasm. |
3) present in plastids and mitochondria. |
4) sometimes found in the outer membrane of the nucleus also. |
5) produced in the nucleolus of the nucleus. |
6) made of RNA and proteins. |
7) membrane-less organelle. |
8) it has two subunits:- a small unit(70s) and a large unit(80s). |
9) 70s ribosome: present in prokaryotic cells, mitochondria and chloroplast. |
10) 80s ribosome: present in eukaryotic cell, ER, cytoplasm of ER, outer membrane of the nucleus. |
VACUOLE
1) single membrane bound organelle. |
2) types of vacuoles: food, gas, contracile(only in aquatic animals) |
-functions- |
storage, maintains water balance in the cell, helps in excretion. |
DIFFERENCES BETWEEN MITOSIS AND MEOSIS.
mitosis |
meosis |
1) forms 2 daughter cells. |
1) on cell forms 4 daughter cells. |
2) also known as equational division. |
2) also known as reductional division. |
3) occurs in vegetative cells or somatic cells. |
3) occurs in gametes or germinal cells |
4) daughter cells have same number of chromosomes. |
4) daughter cells will have half the number of total chromosomes. |
5) helps in growth and healing of an injury. |
5) formation of gametes for reproduction. |
DIFFERENCES BETWEEN SER AND RER
SER |
RER |
1) ribosomes are present. |
1) ribosomes are absent. |
2) protein synthesis. |
2) lipid synthesis. |
3) mainly has cisternae. |
3) mainly has vesicles and tibules. |
CHROMOSOMES
during cell division, chromatin condenses to form chromosomes. |
chromosomes contain DNA along with proteins called Histones which helps in the packing of DNA. |
DNA is made of nucleic acids. |
NUCLEIC ACIDS: |
1) made up of sugar(deoxyribose sugar-> 5 carbon compound) |
2) nitrogenous bases-> adenine, guanine, cytosine, thymine. (thymine is only in DNA, in RNA it is Uracil) |
Adenine = Thymine (double bonding) |
Guanine ≡ Cytosine (triple bonding) |
DIFFERENCES BETWEEN ANIMAL AND PLANT CELL
plant cell |
animal cell |
1. nucleus is situated in the peripheral area. |
1. nucleus is in the center of the cell. |
2. cell wall is present. |
2. cell wall is absent. |
3. vacuoles are large and present. |
3. vacuoles are small and temporary. |
4. plastids are present. |
4. plastids are absent. |
5.lysosomes are absent. |
5. lysosomes are present. |
6. centrosomes are absent. |
6. centrosomes are present. |
7. cytoplasmic division happens by cell plate formation. |
7. cytoplasmic division happens by cell furrow formation. |
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1. nucleus is in the peripheral area. |
DIFFERENCES BETWEEN ANIMAL AND PLANT CELL
plant cell |
animal cell |
1. nucleus is in the peripheral area. |
THE CELL THEORY
1) every organism is made up of cells. |
2) cells are the structural and functional unit. |
3) all cells arise from prexisting cells. (omicellula-e-cellula |
MODERN CELL THEORY ADDITIONS: |
4) all cells contain genetic material. |
5) some organisms can divide again and again and give rise to organs or organisms. |
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