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2.1.3 Relation between the Density of Organelles and the Function of Cells

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Density of Organelle

  1. Density of organelle is refering to the abundance of certain organelles found in a cell.
  2. The density of an organelle in a cell is related to the specific function of the cell.
  3. Below are examples of high density of certain organelle and their reason.

Cell with high density of chloroplast.

Palisade mesophyll cell
Reason:
To trap sunlight to synthesise carbohydrate during photosynthesis.


Cell with high density of mitochondria

Sperm cells
Reason: Need energy to move through the uterus towards the Fallopian tubes.


Muscle cells
Reason: Contraction of muscle during movement need a lot energy


Meristem Cells
Reason: Meristem cells in the plant shoots and roots are involved in cell division to produce new cells for growth. It needs a lot of energy for the activities.

Cell with high density of endoplasmic recticulum

Cells in salivary gland
Reason: Active in synthesing and secreting digestive enzyme

Pancreatic Cells
Reason: Active in synthesing and secreting hormone and enzyme

2.1.2 Comparison between the Animal Cell and Plant Cell

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Similarities of Animal Cell and Plant Cell

  1. Both animal cells and plant cells have
    1. plasma membrane
    2. nucleus with nucleic bounded by nuclear membrane
    3. cytoplasm
    4. ribosome
    5. mitochondria
    6. golgi apparatus
    7. endoplasmic recticulum



Differences between Animal Cells and Plant Cells

Animal Cells Plant Cells
Cell Wall Absent Present
Cytoplasm Present throughout the cell. Present, but usually confined to a thin layer at the edge of the cell.
Chloroplast Absent Present
Vacuole Present in some animall cells. Normally small and distributed throughout the cell. Present. Large and filled with cell sap.
Nucleus Normally in the middle of the cell Normally at the edge of the cell
Lysosome Present Normally absent
Centriole Present Absent
Storage Granule Mainly as glicogen Mainly as starch
Shape Do not have fixed shape Have fixed shape
Size Usually smaller than plant cell Usually bigger than animall cell
Cilia and Flagella Present (Usually) Absent
Secretion Produces a variety of secretions. Produces few secretions.

2.6 Hormonal Coordination in the Body

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Hormonal Coordination in the Body

1. Hormones are the chemical substances produced by the ductless glands called endocrine glands.
2. Hormones are produced in a small quantity and are carried by the blood circulation system to all parts of the body.


2.6.1 Human Endocrine System
1. The endocrine system is made up of endocrine glands, which are ductless glands that secrete hormone directly into the bloodstream.
 

Human endocrine system and the location of endocrine glands




Endocrine glands
Hormones
Function of hormone
Pituitary gland
•  names of hormones not required
•  Master gland that controls and regulates the secretion of hormones by other endocrine glands.
•   Controls the growth of body.
•   Controls the reabsorption of water.
•   Controls other endocrine glands like ovary and testes.
Thyroid gland
•  Thyroxine
(contains iodine)
•  Main source of iodine is seafood.
•   Controls metabolic rate.
•   Controls the physical and mental growth
Pancreas
•  Insulin
•   Glucagon
Controls sugar level in the blood by:
•  Insulin converts excess glucose into glycogen.
•   Glucagon changes glycogen into glucose.
Adrenal glands
•   Adrenaline
(secreted during situations of emergencies, under stress, fear or anxiety)
• Increase heartbeat.
• Increase metabolic rate.
• Increase breathing rate.
• Converts glycogen into glucose.
Testes
(produces
the male sex hormones)
•   Testosterone
•  Controls the development of male secondary characteristics such as deepening of voice armpit hair and moustache.
•  Production of sperms.
Ovaries
(produces
the female sex hormones)
•   Oestrogen
•  Progesterone
•  Controls the development of female secondary characteristics such as development of breast and enlargement of pelvis.
•  Controls the menstrual cycle and ovulation.
•   Stimulates development of milk glands during pregnancy.



Effects of Hormonal Imbalance on Health
Hormones
Effect of excessive hormone
Effect of deficiency of hormone
Growth hormone
•   gigantism
•  dwarfism
Thyroxine
•  Increase metabolic rate
•  Increase heartbeat
•  Increase sweating
•  Protruding eyes
•  Metabolic rate decreases
•  Retarded growth in Children
• Causes goitre
Insulin
•  Shortage of glucose in the blood.
•  May lead to coma and fatal.
•  Diabetes Mellitus
Adrenaline
• High blood pressure.
•  High salt concentration in blood.
•  Blood sugar level increases.
•  Muscles weaken.
•  Ability to overcome stress reducing.
•  Excessive salt and water in the body (Addison disease).
Testosterone
•  Extremely masculine
•  Incomplete development of secondary sexual characteristics.
•  Immature sperms produced.
Oestrogen
Progesterone
• Extremely feminine.
• Baby born before the complete gestation period.
•  Incomplete development of secondary sexual characteristics.
•  Irregular menstrual cycle
•  Infertility
•  Miscarriage



2.1.1 Components of a Cell

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  1. Each cell consists of a plasma membrane and protoplasm
  2. The protoplasm consist of cytoplasm and nucleus.
  3. Cytoplasm contains many types of organelles.
  4. The following is the illustration of the animal cell and plant cell.
(Animal Cell)


(Plant Cell)

Non-Organelle

Plasma Membrane

  1. The plasma membrane separates the content of the cell from its external environment.
  2. It regulates the movement of substances entering and leaving the cell.
  3. It also allows the exchange of nutrients, respiratory gases and wastes products between the cell and its environment

Cytoplasm

  1. The cytoplasm contain variety of organelle.
  2. The function of the cytoplasm is to maintain the shape of the cell.
  3. It acts as a medium for the biochemical reactions occur within the cell
  4. It also store chemical substances such as glicogen granules (in animal cells), starch granules (inplant cells) and enzymes.


Cell Wall

  1. The cell wall only contain in plant cell. It support the cell and the plant and maintain the shape of the cell.
  2. It also prevents the cell from bursting when too much water enters the cell through osmosis.
  3. It allows substances to move through it.

Nucleus

  1. The nucleus contains the genetic material of a cell.
  2. It controls the activities of the cell.
  3. It also produces ribosomes and ribonucleic acids(RNA).

Organelle

Endoplasmic Recticulum (ER)

- Rough Endoplasmic Recticulum:

  1. Transporting the newly synthesised protein.
  2. Involve in the systhesis of protein.
  3. Provides surface for chemical reaction

- Smooth Endoplasmic Recticulum:

  1. Transporting lipids and glycerols.
  2. Synthesising lipids and other non-protein substances.

Mitochonrion

  1. Produces ATP (Adenosine triphosphate.)
  2. Site of energy production through cellular respiration.

Ribosomes

  1. Site for synthesising protein.
  2. Golgi Apparatus
  3. Site for the production of enzyme andlysosome.
  4. Produces polysacharides, glycoproteins andsecretory enzyme.
  5. Storing and modifying carbohydrate and glycoprotein.
  6. Transport and store lipid.

Vacuole

  1. Stores food (Carbohydrate, amino acid) and water.
  2. Support herbaceous plants when it is turgid.
  3. Stores organic waste (in leaf cells).

Chloroplast

  1. Contain chlorophyll and hence a site for photosynthesis to take place.

Centrosome


  1. The centrosome is served as the main microtubule organizing center (MTOC) of the animal cell as well as a regulator of cell-cycle progression.
  2. It form spindle fibres during cell division in animal cell.


Lysosomes


  1. Lysosomes contain hydrolytic enzymes that digest or break down complex organic molecules such as proteins, polysaccharides and lipids.
  2. The enzymes eliminate worn out organelles and damaged organelles.

Golgi Apparatus


  1. The golgi apparatus processes proteins and lipids from the endoplasmic reticulum
  2. The products are sorted by the Golgi Apparatus and packaged into vesicles
  3. The vesicles then release their contents outside the cell.
  4. It also responsible to the formation of lysosomes.

2.5.5 Voluntary Actions and Involuntary Actions

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Voluntary Actions and Involuntary Actions

1. Voluntary actions are actions we are aware of and which are done according to our
intention.
 
2. Voluntary actions are controlled by the cerebrum.
 
3. Involuntary actions take place continuously and automatically in the body, without us
being consciously aware of them.

4. Involuntary actions are controlled by the medulla oblongata.



Comparison between voluntary actions and involuntary actions


2.1 Cell Structure and Function

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Theory of Cell

  1. The cell is the basic unit or building block for all living organisms.
  2. All organisms are made up of one or more cells .
  3. Cells are the fundamental and structural unit of life.
  4. A cell is made up of a plasma membrane which contains protoplasm.
  5. Protoplasm is made up of cytoplasm and a nucleus.
  6. A cell consist of the non-organelle structure the organelle structure.

Non-organelle/Organelle Structures of Cell

  1. The non organelle structure of a cell include
    1. Plasma membrane
    2. Cytoplasm
    3. Cell wall (plant cell only)
  2. Whereas the organelle structure of a cell include
    1. Nucleus
    2. Endoplasmic Recticulum
    3. Mitochondrion
    4. Ribosom
    5. Golgi apparatus
    6. Vacuole
    7. Chloroplast (plant cell only)

    Structure of an Animal Cell


    1. Each animal cell is enclosed by a plasma membrane.
    2. Within the plasma membrane is the protoplasm which consists of the cytoplasm and a nucleus.
    3. Animal cells do not have regular shapes.
    (This file is shared under GNU Share Document Licence from  Wikipedia)


    Structure of a Plant Cell


    1. Each plant cell is enclosed by a plasma membrane which is protected by a cell wall.
    2. Again, within the plasma membrane has a nucleus and cytoplasm.
    3. Unlike animal cell, most plant cells have chloroplasts which contain chlorophyll.
    4. Also, a mature plant cell may have a large vacuole which contains cell sap.
    5. Plant cells have a fixed shape because they have cell walls.
    (Onion Cell)

    2.4 Proprioceptors in Maintaining Balance and Body Coordination

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    Proprioceptors in Maintaining Balance and Body Coordination
     
    1. The sense which helps us to detect position and movement of the limbs by using proprioceptors is known as the kinaesthetic sense.
     
     
    2. Proprioceptor is a group of highly sensitive stretch receptors in muscle, tendons and ligaments.
     
    3. Proprioceptors function to maintain body balance, body posture and coordinate the muscular activities.
     
    4. Proprioceptors are important because they are sensitive to being stretched, twisted or compressed. They act as sensory organs.
     
    5. Proprioceptors are able to respond to stimuli and send out nervous impulses along their nerves to the central nervous system.
     


    6. Proprioceptors enable us to know the movement of our limbs without having to watch them.
     
    7. Examples of activities which are helped by kinaesthetic senses are:
    (a)  Playing piano
    (b)  Cycling
    (c)  Rock climbing
    (d)  Wearing shirt
    (e)  Clapping hands
    (f)   Tying shoe laces without looking
     
















    2.3 Nervous Coordination

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    Nervous Coordination
    1. A stimulus is any change which occurs outside or inside the human body that brings about a response.
    2. A receptor is a cell in the sensory organ which detects stimulus and convert the stimulus into electrical impulses.
    3. There are five main types of sensory organs, the eyes, ears, tongue, nose and skin.
    4. The reaction to a stimulus is called response.
    5. A response may be in the form of movement, caused by muscles or in the form of secretions, produced by glands.
    6. Muscles and glands which respond to stimuli are called effectors.
    7. All receptors and effectors are connected to the nervous system by neurones.


     

    Reflex actions
    1. A reflex action is a fast, automatic and involuntary response towards a stimulus. It is carried out without conscious by the brain.
    2. Reflex actions help us to survive and to protect us from dangerous situation. For example, jerking away of hand when in contact with a hot kettle.
    3. Reflex actions take place in the spinal cord.
    4. The path of reflex action is called a reflex arc.
    Flow chart showing reflex action occurring through the spinal cord





    Example of reflex action when hand is pricked by a sharp nail
     


    2.2.2 Types of Neurone

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    Types of Neurone
    There are three types of neurone:
    (a)  Sensory neurone
    (b)  Relay neurone (intermediate neurone)
    (c) Motor neurone



    Characteristics
    Sensory neurone
    Relay neurone
    Motor neurone
    Position in the body
    Present in all parts of the body
    Present in the brain and the spinal cord only
    Present in all parts of the body
    Position of cell body
    In the middle of neurone
    At the centre of neurone
    At the end of neurone
    Length of axon
    Short
    Very short
    Long
    Function
    Transmits impulses from a receptor to the central nervous system
    Transmits impulses from a sensory neurone to a motor neurone
    Transmits impulses from the central nervous system to the effector