The Cell-Basic Unit of Life
Life Science
The Cell.
Living ma er known as protoplasm, cell is smallest unit of protoplasm that exhibits
characteris cs of life.
Cell consists of nucleus, cytoplasm(everything but nucleus).
Cell membranes encloses liquid contents of cell, ground-plasm(hyaloplasm) together
they cons tute cytoplasm.
Chemical Composi on of the Protoplasm
Consist inorganic, organic compounds.
Inorganic components:
- Water: Main component protoplasm; up 90% of org can consist. Serves solvent, medium/reagent chemical reac ons.
- Gases: Oxygen, carbon dioxide are dissolved in ground-plasm.
- Mineral salts: In ionic form e.g., sodium chloride, phosphates, potassium ions.
Organic components:
- Proteins: NB structural component of cell membrane, all enzymes=proteins some hormones=proteins.
- Carbohydrates: Sugars, starch most NB source energy.
- Lipids(fats): Structural component of cell membranes, stored as reserve energy.
- Nucleic acids: DNA, RNA.
Physical Nature of Protoplasm
Water is solvent in biological systems.
Protoplasm is really a composi ons diff types solu on:
- True solu on: Homogenous(all par cles almost same size, not seen naked eye). Salts, sugars, gases dissolved water.
- Suspension: Heterogenous(all par cles seen naked eye, o en sink bo om not s rred). Cell organelles floa ng ground-
plasm is example.
- Emulsion: Solvent, dissolved substance=liquid. Oil droplets dispersed in water form emulsion.
- Colloidal solu ons:
o Par cles of dissolved substance=too big/heavy to float, too small/light to sink to bo om.
o Colloidal par cles some mes have similar charges, repel each other. Remain in suspension.
o Par cles can form strings/clumps (aggregates).
o Aggregates can hold water in spaces between par cles. Proteins form colloidal solu ons.
o In more solid state form solu on in gel state, while more liquid state described sol.
o Endoplasm(ground-plasm in central area cell)= sol state, ectoplasm(gp bordering cell membrane)=gel sate.
o Sol, gel state=reversible. Temp, pressure, pH play role in condi on of protoplasm.
Cellular Structures
,Cell Wall
Found plant cells. Not part of living protoplasm. Found directly outside cell
membrane, formed by cell membrane.
Consist of cellulose fibres impregnated with carbohydrates.
- Primary Cell walls: Consist of fibres arranged disorderly manner. Fibres are
permeated with pec n, sugary substance.
- Secondary cell walls: Consist of neatly arranged fibres permeated with lignin
(woody substance. Some mes contain suberin(water-proof substance) as in bark
of cork oak (Quercus suber).
Func ons:
- Lend support to plant cell. Responsible shape of cell.
- Offer protec on against mechanical injury in plant cell.
Plasmodesmata=thin, cytoplasmic threads that reach through cell wall. Connect cytoplasm
of adjacent cells.
In plants with secondary walls gaps occur from place to place in cell wall. Gaps known as
pits.
When pits surrounded by raised part(collar) known as bordered pit. Pits allow lateral
transporta on.
Cell Membrane
Part living protoplasm. Plays NB role protec on being differen ally permeable.
According to floa ng mosaic model consist 2 layers phospholipids (fats with phosphate ions) in which proteins molecules
move around, like iceberg at sea.
Not sta c structure can change con nuously.
Protein part=hydrophilic, allows water move through.
Phospholipid part-hydrophobic, only allow substances not water soluble to penetrate membrane.
Proteins act carrier molecules take substance through cell against concentra on gradient. Ac ve transport as use energy.
Substances like ions, other small molecules move through ny pores in cell membrane.
Func ons:
- Encloses cell contents.
- Differen ally permeable(controls movement of substances in, out cell).
- Form part cellular immunity system.
- Membranes inside cell e.g., ER play NB role bringing parts cell in contact with one
another.
Transport in Cells
Intracellular transport takes place through diffusion. Osmosis allow transport from cell to cell (intercellular transport).
Diffusion:
- Spontaneous movement of gas/liquid from high to a low concentra on.
- Dissolved substances can therefore spread evenly through groundplasm.
- Substances can also diffuse from cell-cell.
- Tempo influenced by:
o Concentra on gradient in system. Bigger diff in concentra on=faster.
o Temp, higher temp=quicker.
o Pressure in system. When system pressure increases tempo increases.
Ac ve Transport:
- Substances move through membrane against diffusion gradient(low-high concentra on).
Ac ve, because energy used.
- Osmosis: Movement of solvent(water cells) high-low water poten al through differen ally permeable membrane.
- High water poten al raises from many free water molecules in a solu on that can do work(solu on very li le
dissolved molecules). Pure water has highest water poten al.
,Nucleus
Most NB organelle in any cell. Is largest of cellular structures, can o en be seen when using light microscope.
All cells have nucleus, even red blood cells that do not have started out with it when first formed.
It is surrounded by double differen ally permeable nuclear membrane the outer being the ER(Endoplasmic Re culum).
Pores occur in nuclear membrane, bringing nuclear contents into direct contact with groundplasm.
Space between 2 membranes=perinuclear space.
Nuclear plasma is liquid contents of nucleus. The chroma n network(hereditary material) is found in nuclear plasma.
1/more solid bodies found nuclear plasm, nucleolus consist mainly RNA, protein role, probably play role protein synthesis.
Func ons:
- Control of cell metabolism.
- Differen a on and specialisa on of cell. Shape of Chromosomes
- Transfer of hereditary info.
- Reproduc on of cells/organisms.
Orgs divided 2 group prokaryotes(not have true nuclei, chroma n not surrounded by membrane), Eukaryotes(have it).
Bacteria=prokaryotes, most unicellular, mul cellular orgs=eukaryotes.
Chroma n network consist of macromolecule DNA(deoxyribonucleic acid).
In cell division chroma n network shortens, thickens to become visible as chromosomes(bear hereditary factors(genes)).
Number chromosomes per cell=unique characteris cs that differs from species-species.
Each cell human body contains 46 chromosome, sperm, egg cells have 23 each.
Number Name
1 Rough Endoplasmic Re culum
2 Nuclear Membrane
3 Nuclear Pore
4 Nucleolus
5 Ribosomes
6 Nuclear Plasms
7 Chroma n Network
Mitochondrion
Regarded as power sta on of cell. Responsible cellular respira on.
Cellular Respira on: Gradual release of energy from energy-rich fuel molecule(glucose) in presence of O2, with H2O, CO2
as waste products.
Energy is temporarily stored in energy carrier of cell ATP, is available for work in cell when necessary.
C6H12O6 +6O2 6C02 + 6H2O+ ATP
Mitochondria(plural)=small oval shaped structures surrounded by double membrane.
Inner membrane is folded to increase surface, surrounds the liquid part of the organelle(matrix).
Folds of inner membrane called cristae, serve as basis for enzymes systems responsible cellular respira on.
Mitochondrion also contain DNA, but in specific ring structure called a plasmid.
Mitochondrial DNA(mt DNA) transferred from mother via egg cell to next genera on.
Gene c history can be studied by using DNA at least on maternal side.
Mitochondrial DNA can also be used to iden fy somebody/connect person to a crime.
, Endoplasmic Re culum (ER)
System of membranes in cell that:
- Brings cell contents in contact with outside
environment(extracellular environment).
- Enlarges internal surface of cell.
- Acts as internal transport system.
- Serves as basis for a achment for ribosomes, therefore playing a
role in protein synthesis.
ER with ribosomes also known as granular(GER) or coarse ER.
Smooth/agranular ER (AER) do not have ribosomes.
Ribosomes
Small, roundish structures found in ground plasm especially on ER.
Bases of protein synthesis.
Gene c code for the various proteins brought from DNA in nucleus to ribosomes by RNA.
Amino acids are arranged, bound in certain sequence on ribosomes.
Golgi Apparatus
Membrane system consis ng of number of dictyosomes. It is system of
stacked flat membrane vesicles.
Func ons:
- Associated with secre on in the cell.
- Plays role in forming of other membrane systems like ER.
- It processes, changes, sorts proteins.
- Plays role in forma on of lysosomes(structure containing diges ve
enzymes that burst open and eat cell if the cell dies).
Plas ds
Organelles found in plant cells only.
There are three types: Chloroplast, Leucoplast, Chromoplasts.
Chloroplast:
Oval Shapes structures surrounded by double membrane. Liquid content
known as stroma.
Layers of membranes(lamellae) found in stroma.
Thickenings known as thylakoids occur on lamellae. Stack thylakoids called granum.
Thylakoids contain enzymes, co-enzymes, cytochromes, various pigments.
Most prominent pigment= green chlorophyll and yellow, orange, red carotenoids.
Pigments absorb light for photosynthesis gives colour to plant structures.
In chloroplast carotenoids masked by chlorophyll resul ng in green chloroplast, cause
green parts of plant.
Photosynthesis take place in chloroplast.
Chromoplast:
Structure same as chloroplast, but it does not contain chlorophyll. So, carotenoids get to show their colours.
Found in most plant parts, responsible for colour of flowers, leaves that change colour in autumn fruit that ripen, change
colour.
Happens when chloroplast loose their chlorophyll, changes to red/orange/ yellow.
Life Science
The Cell.
Living ma er known as protoplasm, cell is smallest unit of protoplasm that exhibits
characteris cs of life.
Cell consists of nucleus, cytoplasm(everything but nucleus).
Cell membranes encloses liquid contents of cell, ground-plasm(hyaloplasm) together
they cons tute cytoplasm.
Chemical Composi on of the Protoplasm
Consist inorganic, organic compounds.
Inorganic components:
- Water: Main component protoplasm; up 90% of org can consist. Serves solvent, medium/reagent chemical reac ons.
- Gases: Oxygen, carbon dioxide are dissolved in ground-plasm.
- Mineral salts: In ionic form e.g., sodium chloride, phosphates, potassium ions.
Organic components:
- Proteins: NB structural component of cell membrane, all enzymes=proteins some hormones=proteins.
- Carbohydrates: Sugars, starch most NB source energy.
- Lipids(fats): Structural component of cell membranes, stored as reserve energy.
- Nucleic acids: DNA, RNA.
Physical Nature of Protoplasm
Water is solvent in biological systems.
Protoplasm is really a composi ons diff types solu on:
- True solu on: Homogenous(all par cles almost same size, not seen naked eye). Salts, sugars, gases dissolved water.
- Suspension: Heterogenous(all par cles seen naked eye, o en sink bo om not s rred). Cell organelles floa ng ground-
plasm is example.
- Emulsion: Solvent, dissolved substance=liquid. Oil droplets dispersed in water form emulsion.
- Colloidal solu ons:
o Par cles of dissolved substance=too big/heavy to float, too small/light to sink to bo om.
o Colloidal par cles some mes have similar charges, repel each other. Remain in suspension.
o Par cles can form strings/clumps (aggregates).
o Aggregates can hold water in spaces between par cles. Proteins form colloidal solu ons.
o In more solid state form solu on in gel state, while more liquid state described sol.
o Endoplasm(ground-plasm in central area cell)= sol state, ectoplasm(gp bordering cell membrane)=gel sate.
o Sol, gel state=reversible. Temp, pressure, pH play role in condi on of protoplasm.
Cellular Structures
,Cell Wall
Found plant cells. Not part of living protoplasm. Found directly outside cell
membrane, formed by cell membrane.
Consist of cellulose fibres impregnated with carbohydrates.
- Primary Cell walls: Consist of fibres arranged disorderly manner. Fibres are
permeated with pec n, sugary substance.
- Secondary cell walls: Consist of neatly arranged fibres permeated with lignin
(woody substance. Some mes contain suberin(water-proof substance) as in bark
of cork oak (Quercus suber).
Func ons:
- Lend support to plant cell. Responsible shape of cell.
- Offer protec on against mechanical injury in plant cell.
Plasmodesmata=thin, cytoplasmic threads that reach through cell wall. Connect cytoplasm
of adjacent cells.
In plants with secondary walls gaps occur from place to place in cell wall. Gaps known as
pits.
When pits surrounded by raised part(collar) known as bordered pit. Pits allow lateral
transporta on.
Cell Membrane
Part living protoplasm. Plays NB role protec on being differen ally permeable.
According to floa ng mosaic model consist 2 layers phospholipids (fats with phosphate ions) in which proteins molecules
move around, like iceberg at sea.
Not sta c structure can change con nuously.
Protein part=hydrophilic, allows water move through.
Phospholipid part-hydrophobic, only allow substances not water soluble to penetrate membrane.
Proteins act carrier molecules take substance through cell against concentra on gradient. Ac ve transport as use energy.
Substances like ions, other small molecules move through ny pores in cell membrane.
Func ons:
- Encloses cell contents.
- Differen ally permeable(controls movement of substances in, out cell).
- Form part cellular immunity system.
- Membranes inside cell e.g., ER play NB role bringing parts cell in contact with one
another.
Transport in Cells
Intracellular transport takes place through diffusion. Osmosis allow transport from cell to cell (intercellular transport).
Diffusion:
- Spontaneous movement of gas/liquid from high to a low concentra on.
- Dissolved substances can therefore spread evenly through groundplasm.
- Substances can also diffuse from cell-cell.
- Tempo influenced by:
o Concentra on gradient in system. Bigger diff in concentra on=faster.
o Temp, higher temp=quicker.
o Pressure in system. When system pressure increases tempo increases.
Ac ve Transport:
- Substances move through membrane against diffusion gradient(low-high concentra on).
Ac ve, because energy used.
- Osmosis: Movement of solvent(water cells) high-low water poten al through differen ally permeable membrane.
- High water poten al raises from many free water molecules in a solu on that can do work(solu on very li le
dissolved molecules). Pure water has highest water poten al.
,Nucleus
Most NB organelle in any cell. Is largest of cellular structures, can o en be seen when using light microscope.
All cells have nucleus, even red blood cells that do not have started out with it when first formed.
It is surrounded by double differen ally permeable nuclear membrane the outer being the ER(Endoplasmic Re culum).
Pores occur in nuclear membrane, bringing nuclear contents into direct contact with groundplasm.
Space between 2 membranes=perinuclear space.
Nuclear plasma is liquid contents of nucleus. The chroma n network(hereditary material) is found in nuclear plasma.
1/more solid bodies found nuclear plasm, nucleolus consist mainly RNA, protein role, probably play role protein synthesis.
Func ons:
- Control of cell metabolism.
- Differen a on and specialisa on of cell. Shape of Chromosomes
- Transfer of hereditary info.
- Reproduc on of cells/organisms.
Orgs divided 2 group prokaryotes(not have true nuclei, chroma n not surrounded by membrane), Eukaryotes(have it).
Bacteria=prokaryotes, most unicellular, mul cellular orgs=eukaryotes.
Chroma n network consist of macromolecule DNA(deoxyribonucleic acid).
In cell division chroma n network shortens, thickens to become visible as chromosomes(bear hereditary factors(genes)).
Number chromosomes per cell=unique characteris cs that differs from species-species.
Each cell human body contains 46 chromosome, sperm, egg cells have 23 each.
Number Name
1 Rough Endoplasmic Re culum
2 Nuclear Membrane
3 Nuclear Pore
4 Nucleolus
5 Ribosomes
6 Nuclear Plasms
7 Chroma n Network
Mitochondrion
Regarded as power sta on of cell. Responsible cellular respira on.
Cellular Respira on: Gradual release of energy from energy-rich fuel molecule(glucose) in presence of O2, with H2O, CO2
as waste products.
Energy is temporarily stored in energy carrier of cell ATP, is available for work in cell when necessary.
C6H12O6 +6O2 6C02 + 6H2O+ ATP
Mitochondria(plural)=small oval shaped structures surrounded by double membrane.
Inner membrane is folded to increase surface, surrounds the liquid part of the organelle(matrix).
Folds of inner membrane called cristae, serve as basis for enzymes systems responsible cellular respira on.
Mitochondrion also contain DNA, but in specific ring structure called a plasmid.
Mitochondrial DNA(mt DNA) transferred from mother via egg cell to next genera on.
Gene c history can be studied by using DNA at least on maternal side.
Mitochondrial DNA can also be used to iden fy somebody/connect person to a crime.
, Endoplasmic Re culum (ER)
System of membranes in cell that:
- Brings cell contents in contact with outside
environment(extracellular environment).
- Enlarges internal surface of cell.
- Acts as internal transport system.
- Serves as basis for a achment for ribosomes, therefore playing a
role in protein synthesis.
ER with ribosomes also known as granular(GER) or coarse ER.
Smooth/agranular ER (AER) do not have ribosomes.
Ribosomes
Small, roundish structures found in ground plasm especially on ER.
Bases of protein synthesis.
Gene c code for the various proteins brought from DNA in nucleus to ribosomes by RNA.
Amino acids are arranged, bound in certain sequence on ribosomes.
Golgi Apparatus
Membrane system consis ng of number of dictyosomes. It is system of
stacked flat membrane vesicles.
Func ons:
- Associated with secre on in the cell.
- Plays role in forming of other membrane systems like ER.
- It processes, changes, sorts proteins.
- Plays role in forma on of lysosomes(structure containing diges ve
enzymes that burst open and eat cell if the cell dies).
Plas ds
Organelles found in plant cells only.
There are three types: Chloroplast, Leucoplast, Chromoplasts.
Chloroplast:
Oval Shapes structures surrounded by double membrane. Liquid content
known as stroma.
Layers of membranes(lamellae) found in stroma.
Thickenings known as thylakoids occur on lamellae. Stack thylakoids called granum.
Thylakoids contain enzymes, co-enzymes, cytochromes, various pigments.
Most prominent pigment= green chlorophyll and yellow, orange, red carotenoids.
Pigments absorb light for photosynthesis gives colour to plant structures.
In chloroplast carotenoids masked by chlorophyll resul ng in green chloroplast, cause
green parts of plant.
Photosynthesis take place in chloroplast.
Chromoplast:
Structure same as chloroplast, but it does not contain chlorophyll. So, carotenoids get to show their colours.
Found in most plant parts, responsible for colour of flowers, leaves that change colour in autumn fruit that ripen, change
colour.
Happens when chloroplast loose their chlorophyll, changes to red/orange/ yellow.
