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SPM Biology

3.1 The Plasma Membrane

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The Plasma Membrane

The plasma membrane is a semi-permeable lipid bilayer found in all cells that controls water and certain substances in and out of the cell.

Function of the Plasma Membrane

  1. Protects the cell.
  2. Separates the intracellular components from the extracellular environment.
  3. Controls what enters and exits the cell

Necessities for the Movement of Substances across the Plasma Membrane

  1. To transport nutrients into the cell.
  2. For gases exchange
  3. To excrete metabolic waste.
  4. To maintain the pH value and ionic concentration of the cell.



Substances In and Out through the Membrane


Structure of the Plasma Membrane

Fluid Mosaic Model




Permeability of the Phospholipids Bilayer

The permeability of the phospholipids bilayer is determined by:
  1. the size
  2. the charge and
  3. the polarity
of the substances pass through it.




2.4.2 Cell Organisation (Structured Question 1 & 2)

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Question 1:
Diagram below shows four levels of cell organization in humans.



(a) Complete Table below by naming Level 2 and Level 3. [2 marks]



(b)(i) The cells undergo process P to become specific cells that perform a specific function.
Name process P. [1 mark]

(ii) What is the function of the structure in level 2? [1 mark]

(iii) The structure in level 4 is one of the body systems.
Name this system. [1 mark]

(iv) State one function of the system in (b)(iii). [1 mark]

(c)(i) Name and explain the condition which can cause a blockage in blood vessel W. [3 marks]

(ii) A person is suffering from the condition in (c)(i).
State three effects on the person’s health. [3 marks]



Answer:
(a)
Level 2: Tissue
Level 3: Organ

(b)(i)
Process P: Differentiation

(b)(ii)
Function: able to contract and relax to pump the blood

(b)(iii)
Blood circulatory system

(b)(iv)
Transport oxygen, nutrients and antibodies


(c)(i)
Thrombosis – Deposition of cholesterol inside the lumen of a blood vessel which clogs the blood vessel.
Or
Embolism – Movement of cholesterol inside a blood vessel which clogs the blood vessel and leads to thrombosis.
Or
Arteriosclerosis – Deposition of cholesterol/ fat/ calcium inside the lumen of a blood vessel which cause narrowing of the lumen and leads to clogging.

(c)(ii)
1. Chest pain
2. Stroke
3. Heart attacks


2.4.1 Cell Structure and Function (Structured Question 1 & 2)

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Question 1:
Diagram below shows a plant cell as seen under an electron microscope.

(a)(i) On the diagram, label the structures A, B, C and D. (2 marks)

(a)(ii) State the function of structure A and structure D. (2 marks)


(b) Explain the role of C to maintain cell turgidity. (2 marks)

(c) Every somatic cell which contains structure B has a potential to form a complete new organism.

(i) Name the technique used to produce new plants in large quantities. (1 mark)

(ii) By using one suitable part of the plant, explain the technique in (c)(i). (4 marks)



Answer:
(a)(i)
A: Chloroplast
B: Nucleus
C: Vacuole
D: Golgi apparatus

(a)(ii)
A: Absorbs light energy for photosynthesis.
D: Collects chemical produced and pack them in a membrane to form secretory granules.

(b)
- Maintain the osmotic concentration of the cell sap.
- If the cell is flaccid, more water will enter the cell by osmosis.


(c)(i)
Culture tissue / Cloning

(c)(ii)
- Use shoot / root / meristem issue
- Wash and treat with the sterilizing agent hydrogen peroxide.
- The tissue or explant is cultured in a nutrient medium, at a suitable temperature and pH value.
- Cells divide by mitosis to form a callus.
- The callus differentiates to form a clone.



Question 2:
Diagram below shows the structure of an animal cell.


(a)(i) On the diagram, label the structures R and T. (2 marks)

(a)(ii) Explain the function of the chromosomes. (2 marks)


(b) Explain what will happen to the production of extracellular enzymes if the Golgi apparatus and T are absent. (4 marks)

(c) Explain why the sperm cells contain more mitochondria. (2 marks)

(d) Explain why lysosomes help in eliminating damaged organelles in the cells. (2 marks)


Answer:
(a)(i)
R: Plasma membrane
T: Rough endoplasmic reticulum

(a)(ii)
Chromosomes carry genetic material which is transferred from the parent to the offspring.

(b)
If T (the rough endoplasmic reticulum) is absent, there will be less ribosomes in the cells. Only the free ribosomes in the cytoplasm will synthesise proteins/ enzymes. Without the Golgi apparatus, enzymes which are proteins cannot be packaged or processed to be transported out of the cell.


(c)
Sperm cells need a large amount of energy so that it can swim towards the uterus for fertilization.

(d)
Lysosomes contain hydrolytic enzymes/ lysosomes which will digest/ hydrolyse damages organelles, absorb the useful nutrients and eliminate the waste.

2.2.2e Involvement of Systems in Maintaining an Optimal Internal Environment

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Internal Environment of Multicellular Organism

  1. The internal environment of a multicellular cell is referring to the medium surrounding the cell.
  2. It consists of blood plasma and interstitial fluid. (also called the extracellular fluid)

Homeostasis

Homeostasis is the property of a system, especially a living organism, that regulates its internal environment so as to maintain a stable, constant condition.

Factors Affecting the Internal Environment.

  1. Body temperature
  2. pH value of the blood
  3. Sugar level of the blood
  4. Blood pressure
  5. Osmotic pressure of the blood
  6. Concentration of the oxygen and carbon dioxide in the blood

Importance of Homeostasis

Maintaining a suitable environment for all the enzyme function efficienly, and hence enable all biochemical reactions been carried out at their maximum rate.

Regulation of body temperature

Nervous system Detect changes in body temperature
Integumentary system Produces sweat when the surrounding is hot.
Circulatory system Transports and distributes heat evenly through out the body
Muscular system Shivering to produce heat when the surrounding is cool.

2.2.2d Organ System

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  1. Different organ work together form an organ system.
  2. The human body has eleven different organ system, namely the
    1. Circulatory System
    2. Digestive System
    3. Reproductive System
    4. Endocrine System
    5. Nervous System
    6. Respiratory System
    7. Muscular System
    8. Skeletal System
    9. Excretory System
    10. Lymphatic System (Immune System)
    11. Integumentary System

Circulatory System

Organ: Heart, Blood Vessel
Function: Transport nutrients, gases and wastes to and from cells, helps fight diseases and helps stabilize body temperature and pH to maintain homeostasis.

Digestive System 

Organ: Mouth, Oesophagus, Stomach, Duodenum, Small Intestine, Large Intestine
Function: Breaks down food in the body, into a form that can be absorbed.


Reproductive System

Organ: Males: Testes, penis; Females: Ovaries, uterus, vagina
Function: Reproduce offspring.

Endocrine System

Organ: Pituitary, Thyroid, Adrenal gland, Pancreas, Ovary (female only), testis (male only)
Function: Secrets hormone. Hormones are chemical that play a role in regulating metabolism, growth, development and puberty, and also plays a part in determining mood.


Nervous System

Organ: Brain, Spinal Cord, Peripheral Nerves, Sense Organs
Function: Conduct impulses the the body, spinal cord and brain.


Respiratory System

Organ: Nose, Trachea, Lungs
Function: Allow gas exchange.

Muscular System

Organ: Muscle
Function:
  • Initiates heart beat.
  • Working with the skeletal system in movement and locomotion.



Skeletal System

Organ: Bones, Tendons, Ligaments, Cartilage
Function: 

  • Supports the body.
  • Protects the internal organ.
  • Make red and white blood cells.
  • Plays important role in movement.



Excretory System

Organ: Kidneys, Skin, Lung
Function: Eliminates the waste products of metabolism.


Lymphatic System (Immune System)

Organ: Lymphatic Nodes, Lymphatic Vessels, Spleen, Thymus Galnd
Function: 

  • Remove the interstitial fluid from tissues.
  • Absorbs and transports fatty acids and fats to the circulatory system.
  • Produces immune cells.

(Images by BruceBlaus shared under the Creative Commons Attribution 3.0 Unported license.)

Integumentary System

Organ: Skin
Function: Protects the body from damage,

2.2.2a Cell

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Cell specialisation

  1. Cell specialisation means division of labour among cells. Each type of cell specialises in a specific function.
  2. Importance of Cell Specialisation
    1. Cells can perform specific task with greater efficiency.
    2. Enable multicellular organisms adapt to various environment.

Cell Specialisation in Animal

Cell Function
Red blood cells Transport oxygen
White blood cells Destroy microorganisms. Engulf foreign substance in the blood stream.
Smooth muscle cells Contract and release to produce movement
Nerve cells Transmits nerve impulse


Cell Specialisation in Plant

Cell   Function 
Palisade Mesophyll Cells Carries out photosynthesis
Guard Cells Control the size of the stomata pore to allow gaseous exchange.
Xilem Transport water and mineral salt
Phloem Transport disolved food.


Cell Organisation in Multicellular Organism

Cytology (Cell Biology)

Cytology is an academic discipline that studies cells. It's also known as Cell Biology.

Histology

histology is the study of the microscopic anatomy of cells and tissues of plants and animals.

2.2.2 Multicellular Organism

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  1. Multicellular organisms are organisms that consist of multiple cells (more than one cell).
  2. Multicellular organisms are more complex than unicellular organisms and hence  need many different types of cell to carry out their life processes.
  3. This can be achieved through cell specialisation and cell organisation.
  4. Examples of multicellular organisms are hydra, spirogyra, weeds, flowering plants, vertebrate and invertebrate animals.
(Hydra)



(Spyrogyra)

2.2.1a Unicellular Organism – Amoeba sp

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General Characteristic

  1. Amoeba sp. have no fixed shape.
  2. Their shape changes as they move.
  3. They have protrusions called pseudopodium used for movement and capturing victims.

(Image by Pearson Scott Foresman shared under Creative Commons Attribution-Share Alike 3.0 Unported license.)

Habitat

Amoeba sp. live in water.

Movement

  1. Amoebas have protrusions called pseudopodium used for movement and capturing victims.
  2. Pseudopodium is an extension of cytoplasm
  3. Video below shows how an amoeba move in water.


Recommended Videos

Amoeba in Motion

Reproduction

  1. In a favourable environment, Amoebas sp. reproduce through binary fusion.
  2. Binary fusion is a process where the cytoplasm of an amoeba divides and form two daughter.
  3. Under adverse conditions Amoeba sp. reproduce through spore formation.
  4. The spores are protected by cyst walls which resist to heat, cold and dryness.

Feeding

  1. Amoeba feeds by a process called phagocytosis.
  2. During phagocytosis, amoebas sp engulf a food particle and takes it into its cytoplasm where it forms a food vacuole.
  3. Enzymes are added to digest the food, and the nutrients diffuse through the cytoplasm.

Recommended Videos


Amoeba Biology
 

2.2.1 Unicellular Organism

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  1. Unicellular organisms are simple organisms consisting of only one cell.
  2. Each cell is a complete unit of life that is able to carry out all the living processes.
  3. The main groups of unicellular organisms are 
    1. bacteria, 
    2. archaea, 
    3. protozoa, 
    4. unicellular algae and 
    5. unicellular fungi.
  4. Two important unicellular organisms that you need to know in SPM biology are the Amoeba sp. and Paramecium sp. 

2.2 Cell Organisation

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Unicellular and Multicellular Organism

  1. In general, organisms are divided into two types: 
    1. unicellular organisms
    2. multi-cellular organisms.
  2. Unicellular organisms are the organism with just 1 cell.
  3. Each cell is able to carry out all the functions of life independently.
  4. Examples of unicellular organism
    1. Paramecium
    2. Amoeba
    3. Yeast
    4. Chlamydomonas
  5. Multicellular organisms are the organism made up of more than 1 cell
  6. They are larger organisms that contain many different types of cell to carry out different functions of life.
    1. The living processes of organisms include
      1. Feeding
      2. Locomotion
      3. Reproduction
      4. Respiration
      5. Growth
      6. Excretion
      7. Response to stimuli
      8. Heredity
    (Paramecium. This file was upload by Barfooz at the English Wikipedia.)
    (Yeast)
    (Chlamydomonas)