Chapter 2 Cell Structure And Cell Organisation 2.1 Cell Structure

CHAPTER 2 CELL STRUCTURE AND CELL ORGANISATION 2.1 CELL STRUCTURE AND FUNCTIONS Animal Cell

Plant cell

Density of Organelles in specific cells Types of cells

Function

Sperm cells

Require energy to propel towards fallopian tube for fertilisation Contract and relax to enable movement Require energy for active cell division Absorb sunlight during photosynthesis Synthesise and secrete enzyme Secretes digestive enzymes

Muscles cells Cells in the meristems Mesophyll palisade cells Cells in salivary glands Intestinal epithelium Liver cells Goblet cells in the intestinal and respiratory tract

Detoxification of drugs and poisons Secretes mucus

Organelles found abundantly in the specific cells Mitochondria Mitochondria Mitochondria Chloroplast RER Golgi apparatus SER SER Golgi apparatus

2.2 CELL ORGANISATION Living processes in unicellular organisms -Unicellular organisms can feed,respire,excrete,move,respond to stimuli,reproduce and grow. Eg: Amoeba sp.-living in freshwater / soil water environment

Respiratio n Responses to stimuli Growth Feeding

Exchange of O₂ and CO₂ occurs through the Plasma membrane by diffusion -Sunlight/acidic solution cause Amoeba to retreat -Favourable stimuli -food causes it to move towards the stimuli Increasing cytoplasm & lining of plasma membrane By Phagocytosis Amoeba sp. Approaches the food Two pseudopodia extend out and enclose the food particles Food particles then packed in a food vacuole Food vacuole fuses with lysosome (contain lysozyme enzyme) Food is digested by lysozyme Nutrients then absorbed into the cytoplasm

When Amoeba moves away undigested food is left behind

Excretion

Locomotio n

-Waste products (CO₂ and NH₃) eliminated through the plasma membrane by diffusion. Osmoregulation -When contractile vacuole filled with water to a maximum size =>contract to expel water By Cytoplasmic projection -Also known as ameboid movement -Extend its pseudopodia  Anchoring the tips on the ground Flow of cytoplasm into the projected pseudopodia

Reproducti on

Amoeba divides  nucleus divides  cytoplasm divides  2 new cells after it grown formed to certain size Cell specialisation in multicellular organisms -human life begin as a single cell known as zygote -zygote undergo repeated division forming embryo -embryo cells grow, change shape and differentiate to carry out specific functions. =>cells can perform their tasks more efficiently. Cell organisation in multicellular organisms Cell  Tissue  Organ  System  Organism Cell organisation in animals System Integument ary Lymphatic Digestive

Circulatory Respiratory Reproducti ve Endocrine Nervous Muscular Excretory Skeletal Example: C Epithelial RBC WBC Nerve

Tissue Epithelial Connective Nerve Muscle

Organ Skin

System Integumenta ry

O Human

Cell organisation in plants -2 types of tissue a) Permanent tissue : i) Epidermal tissue ii) Ground tissue : Parenchyma Collenchyma Sclerenchyma iii) Vascular tissue : Phloem Xylem Epidermal tissue

Ground tissue

Vascular tissue

Phloem

-mostly coated with cuticle -functions a)prevent water loss through evaporation b)prevent infection c)prevent mechanical injury

Parenchyma tissue -thin walls -large vacuole -functions a)storing starch & sugar b)provide support & shape to plants

Collenchyma tissue -uneven thick wall -functions a)support herbaceous plants, young stems & petiols

-consists mainly of sieve tubes -sieve tubes form long continuous tube-like structure -functions a)Transport nutrients to all parts of plants

Xylem -cell wall thickened with lignin -consists mainly of xylem vessels joint together end to end (rootsleaves)

-functions a)Transport water from Sclerenchyma tissue roots -uniformly thickened wall to other parts of plants by b)Provide support & Lignin / dead cell mechanical strength -functions a)support & give mechanical strength to mature parts of plants b)Meristematic tissue -consists of small cells with

-thin walls

-large nuclei -young & dividing actively -not undergone differentiation -located at tip of root & buds of shoots Example: Organ System

-no vacuoles -dense cytoplasm

Flower, Fruit, Leaf , Stem Root

Shoot Root

Regulating the internal environment Internal environment of multicellular organisms -consists of a)Interstitial fluid – fill the spaces between cells =>constantly bathes the cells => nutrients & waste products are exchanged between interstitial fluid & blood plasma (in the blood capillaries) b)Blood plasma The necessity for maintaining an optimal internal environment -Physical & chemical factors within the internal environment must be maintained regardless of the condition outside the cell so that the cell can function optimally and effectively -Homeostasis = maintenance of a relatively constant internal environment for the optimal functions of cells. - Negative Feedaback Mechanism = Mechanism than governs homeostasis

Blood sugar level rises

Pancreas secretes insulin

Blood sugar level falls

Normal Sugar Level

Blood sugar level falls

Pancreas secretes glucagon

Blood sugar level rises

Blood sugar level is maintained by the negative feedback mechanism

Body temperatur e rises

Signals send to the brain (hypothalam us)

Skin receptor detect the changes

.More sweat produced .Blood vessel dilate .Minimise muscle

Normal Body Temperatur

Body temperatur e falls

Skin receptor detect the changes

Signals send to the brain (hypothalam us)

Detected by nervous system

Breathing & Pulse rate increased

.Less sweat produced .Blood vessel constrict .Muscle contract-

Normal Body Temperature is maintained by the negative feedback mechanism

Content of CO₂ increased

CO₂ exhaled O₂

Normal Content of CO₂

Content of CO₂ decreased

Detected by nervous system

Breathing & Pulse rate decreased

Less CO₂ exhaled

Normal content of CO₂ is maintained by the negative feedback mechanism