Grade 10 Life Sciences Summary

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.