Comparison between Animal Cell (AC) and Plant Cell (PC)

1. Mitochondrion (pl: Mitochondria): AC and PC

spherical / rod-shaped organelles two membranes : Inner membrane – form cristae & Outer membrane – regular and

smooth an energy source site of cellular aerobic respiration produces ATP (adenosine triphosphate)

2. Nucleus (pl: Nuclei): AC and PC

contains the genetic material regulates and controls the activities of the cell an organelle bounded by double (2) layers of nuclear membrane with pores and

selectively permeable responsible for all cellular structure, chemical functions, growth and reproduction separates the genetic materials (chromatin) from cytoplasm

3. Nucleolus: AC and PC

spherical structure within the nucleus consists of DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) and proteins visible when the cell is not dividing synthesis RNA which is needed to make ribosomes

4. Nucleoplasm: AC and PC

fluid contained within the nucleus highly viscous solid made up of the chromatin and the nucleolus

5. Chromosomes

thread-like structures (consists of genetic material) appears as chromatin spread throughout the nucleus in the form of tiny granules chromatin condenses into chromosomes (during cell division) carry genetic information in its DNA

6. Ribosomes: Ac and PC

small dot-like organelles protein synthesis consist of RNA (ribonucleic acids) smallest cellular organelles

attached on the surface of ER and occur freely in cytoplasm

7. Endoplasmic reticulum (ER): AC and PC

connected to the nuclear membrane synthesises proteins, steroids and lipids collects , stores and distributes protein, steroids and lipids exists as rough ER and smooth ER Rough ER: covered with ribosomes, flat sealed sac which continued from the nuclear

membrane, transports protein, and have a large surface area for chemical reactions. Smooth ER: does not have ribosomes, transports lipids and presents in large amounts of

cells.

8. Plasma membrane: AC and PC

cell membrane thin membrane surround the cytoplasm of a cell selectively permeable / semi permeable a protective and selective outer barrier consists of phospholipids and protein molecules

To be continued.. Upcoming post involves – Golgi apparatus/body, Cytoplasm, Lysosome, Centriole, Vacuole, Cell wall, Chloroplast.

9. Golgi apparatus / Golgi body: AC and PC

bound sacs processes , packages and transport molecules synthesised in the cell forms lysosomes transports and stores lipids synthesis of carbohydrate from hormone changes protein into glycoprotein excretes waste products out of the cell

10. Cytoplasm: AC and PC

aqueous solution (except nucleus) stores water, enzymes, nutrient, salts and dissolved gases provided support, shape and protects the cell organelles medium for metabolic reactions provides substances

11. Lysosome: AC

sac-like organelle with one membrane digest proteins, lipids and carbohydrates

removes undigested materials releases enzymes to digest external materials

12. Centriole: AC

are paired cylindrical organelles nine tubes with three tubules each produces spindle during cell division (mitosis and meiosis) migrate to the opposite poles of the cell (during cell division – will be discussed in

Chapter 5 Cell Division)

13. Vacuole: AC (temporary / lower class species) and PC

small cavity in the cytoplasm bound by a single membrane filled with cell sap storage of food (protein, oil and water) some vacuoles remove metabolic waste functions as cell expansion Amoeba: food vacuoles (phagocytosis) Paramecium: contractile vacuoles (expel water)

14. Cell Wall: PC

rigid and tough cellulose layer surrounding the plasma membrane (cell membrane) protects and supports the cell maintains the shape prevents the cell from busting (excessive intake of water) allows substances to move freely through the cell wall

15. Chloroplast: PC

disc / lens-shaped organelle have two membranes: inner and outer membrane contains chlorophyll in the grana to trap sunlight energy carry out photosynthesis in the chlorophyll storage of food and pigments

Keys:

AC and PC = similarities AC or PC = differences (Carbohydrates storage: AC = Glycogen / PC = Starch)

Organelles – (little organ) tiny structures inside a cell that perform specific functions for a cell. Example: mitochondria, lysosome and chloroplast.

Mitochondria

Animal: High density at sperm cells (at middle piece to provide sufficient energy for motive power), flight muscle cells (bird / avian), liver cells, meristematic / meristemic cells (involve with cell division), kidney cells, heart muscle cells, brain cells.

Chloroplasts

Plant: High density at palisade mesophyll (leaf: below upper epidermis). It functions to trap sunlight to synthesise sugar during photosynthesis.

The Uniqueness of The Cell

A cell is unique:

1. Specialisation 2. Division of labour 3. Coordination and integration

Example of specialisation of cells :

Animal – smooth muscle cell, neuron (nerve cell), white blood cell, red blood cell (erythrocyte), cheek cell (lining epithelial cell), sperm, ovum cell (the biggest cell in human)

Plant – palisade mesophyll cell, xylem, phloem, guard cell.

Cell Organisation

Unicellular – A single cell performs all the basic life process. Example: Amoeba sp., Paramecium sp., Chlamydomonas, Bacteria and Euglena.

Multicellular – An organism consists of more than one cell. Each group of cell specialized to carry our life processes. Example: Homo sapien (human), animals and plants. It has five levels of organisation

1. Cells: basic units of structure and function.Example: Red blood cells and xylem vessel cells.

2. Tissues: made up of cells with similar in structure and function.Example: Epithelial tissues and vascular tissues.

3. Organs: made up of tissues that perform a specific function.Example: Heart and flower.

4. System: two of more organs that perform a specific function.Example: Digestive system and root system.

5. Organisms: whole living thing that carry out all the basic life processes.Example: Human and durian tree.

Cell Organisation (Unicellular) in Amoeba sp. (lives in freshwater ponds) and Paramecium sp. (lives in soil and moist area)

1. Cell structure

Amoeba sp.: plasma membrane, food vacuole, contractile vacuole, pseudopodium, nucleus, ectoplasma, endoplasm.

Paramecium sp.: food vacuole, posterior contractile vacuole, cytostome, gullet, oral groove, cilia, macronucleus, micronucleus, anterior contractile vacuole.

2. Locomotion

Amoeba sp.: Pseudopodium (false foot) helps it to move forward slowly and it is known as amoeboid movement.

Paramecium sp.: Hair-like cilia to beat against water. It beats its cilia backwards diagonally (swim forward) and it rotates on its axis. It beats its cilia forward (swim backwards).

3. Feeding

Amoeba sp.: Omnivore. Eat bacteria, plant cells, algae and other microscopic organisms.

1. Entrapment – extend pseudopodium. 2. Engulfment – engulf tiny food (phagocytosis) with its pseudopodia. 3. Digestion – food enclosed in food vacuole 4. Absorption – enzyme digests the bacteria

5. Egesting – expel indigestible material.

Paramecium sp.: Eat bacteria, organic material and other microscopic organisms.

1. Sweeping – movement of cilia. Food moves along the oral groove into the gullet and cytostome.

2. Digestion – food vacuole circulates round the cell. 3. Elimination – undigested food is eliminated at the anal pore.

4. Reproduction

Amoeba sp.: two types of reproduction.

1. Binary Fission – nucleus divides (favourable condition) and then follows by division of cytoplasm. Two daughter cells are formed (mitotic division).

2. Spore Formation – spores form (bad condition) and germinate into new amoeba under favourable condition.

Paramecium sp.: two types of reproduction.

1. Binary Fission – micronucleus undergoes mitosis (favourable condition). Macronucleus begins to elongation and form two. Cell content divide and two daughter cells are formed.

2. Conjugation (Sexual reproduction) – two same species parent paramecia exchange genetic material of their micronuclei. Each parent divides and forms four daughter cells.

5. Osmoregulation

Amoeba sp.: water moves into the cell by osmosis and prevention of bursting, it has a contractile vacuole.

Paramecium sp.: water moves into the cell by osmosis and prevention of bursting, it has two contractile vacuoles.

6. Respiration

Amoeba sp. and Paramecium sp. (both): exchange gases throughout the whole cell membrane

7. Excretion

Amoeba sp. and Paramecium sp. (both): waste products are ammonia and carbon dioxide by diffusion. Solid waste in paramecium is expelled through its anal pore.

Cell Organisation (Multicellular) in Human

1. Cells: Epithelial cells, muscle cells, white blood cells, red blood cells, sperm, nerve cells.

2. Tissues: Epithelial tissue, smooth muscle tissue, connective tissue, skeletal tissue, nerve tissue.

3. Organs: Stomach, heart, kidney, lung, liver. 4. Systems: Circulatory system, respiratory system, digestive system, excretory system,

muscular system, lymphatic system, integumentary system, skeletal system, nervous system, endocrine system, reproductive system.

5. Organisms: Human.

Cell Organisation in Plant

1. Cells: Parenchyma cells, collenchyma cells, sclerenchyma cells, epidermal cells. 2. Tissues: Epidermal tissue, meristem tissue, vascular tissue. 3. Organs: Leaf organ, flower organ, stem organ, root organ. 4. Systems: Shoot system, root system. 5. Organisms: Plant.

Movement of Substances Across the Plasma Membrane

The plasma membrane is a membrane of biological nature which forms the barrier between the interior of a cell against external environment. However, do not just think of it as a layer which do not have any function. Typically, movement of substances to and from cells to outer environment is controlled (due to its permeability) by the plasma membrane. The key concept here for this topic is to understand the selective-permeability nature of a plasma membrane. The rest of the topic are rather easy and intuitive. Do note that plasma membrane is also known as cell membrane and plasmalemma.

Permeability of the fruit skin

1. Uniqueness of Plasma Membrane (also known as cell membrane):

it is a semi-permeable cell membrane it allows water and certain substances to move in and out of the cell.

2. Importance of Plasma Membrane:

- cells obtain nutrients and gases cells excrete metabolic wastes cells can maintain pH for enzyme activity cells can maintain ionic concentration of the cells for enzyme activity control the types and the amount of substances allow useful substance (hormones/enzymes) to secrete from cells protect cells a boundary between the inside and outside of cell.

3. Structure of the basic unit of plasma membrane

Phospholipid molecule:‘Head’ – hydrophilic: a polar phosphate molecule (philic~loves water / attracted to water)‘Tail’ – hydrophobic: two non-polar fatty acids (phobic~hates water / repelled to water)

Formation:Hydrophilic heads pointing outwardsHydrophobic tails pointing inwards(Bilayer phospolipid)

Fluid Mosaic Model (Protein embedded in the bilayer)

Carrier protein

carrier for some molecules (glucose, amino acids, proteins and nucleic acids) controls the movement of ions and particles (Na+, Ca2+ and K+) Glycoprotein

Glycolipid

combination of lipids and polysaccharides

4. Permeability

Permeable (allow to pass through)

small non-polar molecules (vitamins A, D, E, K, fatty acids, glycerol and steroids)

Impermeable (not allow to pass through but with help of carrier protein and cellular energy, it is allow to pass through)

large polar molecules (glucose, amino acids, mucleic acids and polysaccharides) charged ions (H+, Na+, K+, Cl- and Ca2+)

Substances that are allowed to move in the cell:

CO2 O2 excess H2O waste: nitrogenous

Substances that are allowed to move out of the cell:

CO2 O2 amino acids ionic salts glucose

Materials must be able to move through the plasma membrane in order for the cell cytoplasma to interact with the external environment. Therefore, the movement of soluble substances can occur in several mechanisms:

A. Process of Passive Transport B. Process of Active Transport

A. Passive Transport

i) Simple Diffusion

not selective: lipid-soluble molecules, gases and water. not control by cell. movement of the molecules from a region of higher concentration to a region of lower

concentration.

Factors affecting the rate of diffusion are temperature, size of molecules/ions, diffusion gradient, surface area and diffusion medium.

example: diffusion of oxygen and carbon dioxide at the alveolus.

ii) Osmosis:

only water molecules. not control by cell. movement of water from a region of higher concentration to one of lower concentration

and often occurs across a semipermeable membrane. strong sucrose solution = less water molecule = low water potential. weak sucrose solution = more water molecule = high water potential. example: absorption of water by root hairs.

iii) Facilitated Diffusion:

very specific: glucose, nucleic aicds, amino acids, protein and mineral ions. control by cell. transport of molecules (only certain molecules) across the outer membrane of living cell

by a process of carrier protein (hydrophilic group) / channel protein (Ions: Na+, Ca2+, K+) within the cell membrane.

normally take place from a region with higher concentration of molecules to a region of lower concentration.

example: absorption of digested food in the villus.

B. Process of Active Transport

very specific: minerals ions and amino acids. control by cell. This process needs carrier proteins and energy (due to against concentration gradient)

from a region of lower concentration to a region of higher concentration). Cell must expend energy that derived from ATP (adenosine triphosphate) example: human nerve cells (sodium ions are constantly transport out of the cell) / ions

intake by root hairs of a plant.

Type of Solution

1. Hypotonic 2. Isotonic 3. Hypertonic

1) Hypotonic

Solute concentration in the external solution is lesser than solute concentration inside the cell.

Water concentration outside the cell is higher than the water concentration inside the cell.

2) Isotonic

Solute concentration in the external solution is equal to the solute concentration inside the cell.

Water concentration inside and outside of the cell is the same.

3) Hypertonic

Solute concentration in the external solution is greater than solute concentration inside the cell.

Water concentration outside the cell is lower than the water concentration inside the cell.

Types of solutions:

Type of Solution

Hypotonic Isotonic Hypertonic

Animal Cell

The cell inflates due to the water molecules enter the cell. Eventually it bursts (thin plama membrane). Example: red blood cell in distilled water.

No change in the size of cell. Net movement of water is zero. Example: red blood cell in 0.85% sucrose solution.

The cell shrinks and becomes soft and dehydrated due to the water molecule leave the cell. Example: red blood cell in 5% sodium chloride solution.

Plant Cell The cell expands and becomes firm / turgid due to the water molecules enter the cell. The rigid cellulose cell wall expands slightly and prevents cell from bursting. Example: strip of potato in distilled water.

No change in the size of cell. Net movement of water is zero. Example: strip of potato in 5% sucrose solution.

The cell becomes flaccid (plasmolysis occurs), vacuole and cytoplasma shrink due to the water molecules leave the cell. Example: strip of potato in 30% sucrose solution.

Application

1. Food is soaked in a concentrated salt solution to prevent bacteria and fungus to survive. 2. Chemical fertiliser (dissolved ions) increases solute concentration (decrease water

molecules) in soil. Therefore, water leaves from the cell sap of the plant which result the plant wither.

Finally, the end of the interesting substance movement over plasma membrane. Do keep note that this might be a popular essay question. Easy to answer but hard to score, so take note of the terminologies and concepts shown above.