[Biology Form 5] Meeting Gametes

Study the following details for a better understanding of gametogenesis and what happens after it.

1. Process and location
   
   • Male - Spermatogenesis in the testes.
   • Female - Oogenesis in the ovaries.
   
   
2. Parent cell for gametogenesis
   
   • Male - Primary spermatocyte.
   • Female - Primary oocyte.
   
   
3. Cell produced after Meiosis I
   
   • Male - Two secondary spermatocytes.
   • Female - One secondary oocyte (X) and one (1st) polar body (Y).
   
   
4. Cell produced after Meiosis II
   
   • Male - Four spermatids.
   • Female -
     
     • From the secondary oocyte (X): One ovum + One polar body.
     • From the first polar body (Y): Two other polar bodies.
   
   
5. What happens to cells produced after Meiosis II?
   
   • Male - Spermatids differentiate into sperms.
   • Female - All three polar bodies will degenerate; only the ovum will survive.
   
   
6. When does Meiosis II occur?
   
   • Male - Immediately after Meiosis I.
   • Female -
     
     • For the first polar body: immediately after Meiosis I.
     • For the second oocyte: only after a sperm penetrates the oocyte.
   
   
7. What happens during sexual intercourse?
   
   • Male - Sperms are ejaculated from a male's penis into a female's vagina.
   • Female - Sperm from a male swim upwards, from a female's vagina, through the cervix, into the uterus and then to the Fallopian tubes.
   
   
8. Site for fertilisation
   
   • Male - none.
   • Female - In the Fallopian tubes of the female reproductive system.
   
   
9. Product of fertilisation
   
   • Male - none.
   • Female - A diploid zygote (containing 46 chromosomes), which then develops into an embryo.

What happens after sexual intercourse?

• Possibility I
  
  • A sperm meets the secondary oocyte and penetrates it.
  • Meiosis II quickly occurs in the secondary oocyte, and an ovum and a polar body is formed.
  • The polar body degenerates.
  • The nucleus of the ovum fuses with the nucleus of the sperm.
  • Fertilisation is successful and a diploid zygote is formed.
  • The female is pregnant.
    
    
• Possibility II
  
  • None of the sperms meet the secondary oocyte. This could mean ovulation has
    
    • not occurred yet;
    • occurred but the secondary oocyte, which can only live for 24 hours, has died.
      
      
  • No fertilisation occurs.
  • No zygote is formed.
  • The female is not pregnant; she gets her next period as usual.

[Biology Form 4] Movement Across The Plasma Membrane

1. Three types of passive transport.

• Simple diffusion
• Osmosis
• Facilitated diffusion

2. TRANSPORT

• Active Transport
  
  
• Passive Transport
  
  • Simple Diffusion: The movement of molecules from region of high concentration to low concentration.
  • The movement of molecules from region of high concentration to a region of low concentration with the help of carrier proteins.
  • Osmosis: The movement of water molecules from dilute solution to a concentrated solution across a Semi permeable membrane.
    

3. The figure below shows the model of the plasma membrane. Label L, M, N, and O shows four types of nutrients. P1, P2 and P3 show three types of protein.

(i) Name the processes labelled L, M, N, O.
L : Simple diffusion
M : Fasilitated diffusion
N : Fasilitated diffusion
O : Active transport

(ii) Name the protein labelled P1, P2 and P3.
P1 : Pore protein
P2 : Carrier protein
P3 : Carrier protein

(iii) State two characteristics of the molecules that are transported into the cell by process L.
1. Small
2. Soluble in lipid

4. The figure shows a model of the active transport system that depends on several carrier proteins found in the cell membrane.

(i) Explain what do you understand by active transport.
Movement of particles across the plasma membrane

1. by carrier proteins,
2. against the concentration gradient and
3. requires energy.

(ii) Give an example of active transport in plants.
Ion or mineral uptake by plant root hairs.

(iii) State two differences between active transport and diffusion.
Any two differences – energy, gradient concentration, living membrane.

5. The table below shows the effect of hypotonic, isotonic and hypertonic solution on spinach strips, red blood cells and plant cells.

Hypotonic solution	Isotonic solution	Hypertonic solution
Spinach strip in distill water · Distill water is hypotonic compared to the cell sap. · Water enters into spinach cell through cut surface by osmosis . Epidermis is water proof. · The epidermis layer curved inward.	Spinach strip in 5% sucrose solution · The rate of water entering and leaving the spinach cell through semi permeable mambrane is the same. · The shape of spinach strip remains the same	Spinach strip in 30% sucrose solution
Red blood cell in distill water.	Red blood cell in isotonic solution	Red blood in 30% sodium chloride solution
Plant cell in distill water	Plant cell in isotonic solution	Plant cells in 30% sucrose solution

[Biology Form 4] Cell Structure & Organisation

1. Study the diagrams below. Identify the structures or organelles (A – J) and complete the following table.

	Name of organelle / structure	Function	Consequence if absent
A	Rough endoplasmic reticulum	Transporting proteins	No transportation of proteins
B	Mitochondrion	Site for energy production	Energy cannot be produced
C	Cell wall	Give fixed shape to the cell	Have irregular shape (eg. Animal cell)
D	Smooth endoplasmic reticulum	Transport lipid and glyserol	Lipid and glycerol cannot be transport
E	Nucleus	Control cell activities, contains genetic material.	No cell division, all cell activities stop.
F	Vacuole	Storing nutrients (sugar and amino acid) in its sap.	Cannot store nutrients
G	Cytoplasm	Food storage, medium for metabolic reaction	No site for metabolic reaction
H	Plasma membrane	Controlling entry and exit of substances	No selective barrier
I	Lysosomes	Releases enzymes outside the cell.	No enzymes being released
J	Chloroplast	Carries out photosynthesis	Photosynthesis cannot occur
	Golgi apparatus	Storing and transporting lipids. Produces glycoprotein, polysaccharide and secretory enzyme.

2. Give two differences between animal and plant cell
Any two differences: Cell wall, Vacuole, Centriole, Storage granule, Chloroplast

3.
a) What is cell specialization?
Cell changes in structure or function in order to carry out a specific function.

b) How are cells organised into a multicellular organism?
Cell --> Tissue --> Organ --> System --> Organism

c) Give an example of each type of cell organization in human.
Epithelium Cell --> Epithelium Tissue --> Stomach --> Digestive System --> Human

[Biology Form 4] Plant & Growth

1. Name the phase in which the:
   a) centromeres of chromosomes are lined up at an imaginary plane across the middle of the cell
   
   • Metaphase
   
   b) nucleolus re-forms and the spindle fibres disappear
   
   • Telophase
   
   c) chromosomes are visible as duplicated, thick and short thread-like structures
   
   • Prophase
   
   d) cell is about ready to divide by cytokinesis
   
   • Telophase
   
   e) cell is gathering its energy to begin active mitosis
   
   • Interphase
   
   f) two sister chromatids of each chromosome separate at the centromere
   
   • Anaphase
   
   
   
2. 
   
   
   Based on the diagram, answer the following questions:
   
   a) Name the tissue found at the tip of a plant root.
   
   • Apical meristem
   
   b) Where else in a plant is this tissue usually found?
   
   • Shoot tip
   
   c) State the characteristics of the cells found in the tissue named in (a).
   
   • Very small in size / isodiametric in shape /contain a dense cytoplasm / have a large nucleus
   
   d) When mitosis occurs in these cells, primary growth, which records an increase in length and height, results in the root and shoot.
   
   e) For secondary growth in a plant, mitosis occurs in the vascular cambium, a tissue found between the xylem and phloem tissue in dicotyledons.
   
   f) Mitosis is important for growth because it increases the number of cells in the organism.
   

[Science Form 5] Hydraulic Jack

Operation of a hydraulic jack

The hydraulic jack work on a system of valves,pistons and reservoirs. When the small piston is lifted, liquid rushes in from the reservoir through the open valve P. In the meantime, valve Q is closed. The cylinder connected to the small piston is filled with fluid.

When the small piston is pressed downwards, the pressure produced is transferred onto the liquid to the big piston. At the same time, valve P closes and valve Q opens.

A huge force is created depending on the area of the big piston. The, the lift on the big piston exerted is locked in position.

With another lift from the small piston, the big piston is lifted higher and higher until the desired height is reached. The tyre can then be changed. Work on the undercarriage of the car can also be carried out.

[Chemistry Form 4] Ions In Solution

Swedish chemist Arrhenius defined acids as substances that, when dissolved in water, produce hydrogen ions (H⁺). Eg: When gaseous hydrogen chloride reacts with water, the amount of hydrogen ions in the water increases and hydrochloric acid is thus produced.

HCl (g) ---> H⁺ (aq) + Cl^- (aq)
Acid
(H⁺ producer)

Some of the food and medicines that we take contain acids. Ethanoic (acetic) acid in vinegar and acetylsalicyclic acid in aspirin, for instance.

Contrary to acids, bases are defined as substances that, when dissolved in water, yield hydroxide ions (OH^-). Eg: When sodium hydroxide dissolves in water, the amount of hydroxide ions in the water increases and the alkaline solution is thus produced.

NaOH (s) ---> Na⁺ (aq) + OH^- (aq)
Base
(OH^- producer)

Did You Know?
The compounds responsible for colours in plants are often sensitive to acids and alkalis. For example, blue hydrangeas grow only in acidic soils; in neutral or alkaline soils, they turn to pink.

[Science Form 5] Forceful Fluidity

When a force is applied onto a liquid, the pressure created in the liquid acts in all directions. This is because when liquid is at a standstill, matter in the liquid is distributed evenly, and because of this, pressure is also distributed throughout equally. This property of liquid is captured in the hydraulic principle, which is used widely in hydraulic jacks and hydraulic brakes. The principle is based on the formula: F₁/A₁ = F₂/A₂

A small force F₁ applied on area A₁ is transferred onto a liquid and then onto on an area A₂, which subsequently produces a huge force F₂.

Note: The larger the area, the larger the force is, and thus, a greater weight can be supported.

Eg: A force of 2N is applied on area of 1m². If the area on the other end is 10m², what is the force generated at the same end?
10 times more, which is 2N x 10 = 20N

Also, pressure in liquid is seen as energy per unit volume (using the definition of work). The relationship can be easily explained by the Bernoulli's Equation.

P = Force/Area = F/A = (F x d)/(A x d) = W/V = Energy/Volume