Download - 2.2 cell organisation (biology)
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Cell organisation
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TISSUETissue can be classified into four types:- epithelial tissue- Muscle tissue- Connective tissue- Nerve tissue
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1. Epithelial tissueConsists of one or more layers of cellsAre tightly interconnected and form a continuous layer
over body surfaces(skin&mouth area) and inner lining of cavities(digestive tract&lungs)
Some epithelial tissue undergo changes to form glands(exocrine&endocrine glands)
On skinforms a protective barrier against infection,mechanical injuries & dehydration
Lining of the human intestine form mucus-secreting goblet cells which secrete mucus into the digestive tract
Lining of the tracheaconsists of elongated cells called cilia
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2. Muscle tissueComposed of cells called muscle fibresHave 3 types – smooth muscle, cardiac muscle,
skeletal muscle(a)Smooth muscle(can be found in intestine,blood
vessels, urinary and reproductive tract)- contraction&relaxationresponsible for involuntary
body activities(ex:perilstaltic movement)- Contract more slowly than skeletal muscle but remain
contracted for a longer period of time(b)Skeletal muscle- Voluntary movementscontract & relax to move the
bones(c) Cardiac muscle- Contract to pump blood (involuntary)
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3. Nerve tissueComposed of neuronesSpecialised to detect stimuli and transmit
electrical signals called nerve impulses to muscles or glands
Control and coordinate activities of the body
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4. Connective tissueConsists of various types of cell and fibres separated
by an extracellular matrixi. Loose connective tissuebinds epithelia to
underlying tissues and hold organs in placeii. Dense fibrous connective tissuefound in
tendons & ligamentsiii. Cartilage strong&flexible;provides support to the
nose,ears and covers the ends of bones at jointsiv. Bone protection to organs and support the bodyv. Blood cells regulate,transport& protectvi. Adipose tissue acts as an energy
reserve,insulation&protection
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Red blood cells
Bone
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cartilage
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OrgansIs formed by two or more types of tissue
working together to perform a particular function
Examples: heart,skin,lungs,kidneys,eyes and ears
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SystemsConsists of several organs that work
together to perform a common functionThere are 11 major systems which carry
out major body functions in human
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Cell organisation in plantTwo main types:(i)The meristematic tissues- small cells which have thin walls, large
nuclei,dense cytoplasm & no vacuole- Are young,actively dividing cell which have
not undergone differentiation and are located at the tips of roots and the buds of the shoots
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(ii) The permanent tissues- Tissue that have undergone differentiation or
are still undergoing differentiation- Have three types:(a) Epidermal tissue(b) Ground tissue(c) Vascular tissue
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1. Epidermal tissueOutermost layer that covers the
stem,leaves and roots of young plantsAre flat and have large vacuolesCuticle minimizes water loss & prevent
invasion of diseasesRoot hairsincrease surface area for water
absorptionSpecialised epidermal tissue,ex: guard
cells control the opening & closing of stomata
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Guard cell
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2. Ground tissueConsists of parenchyma tissue,
collenchyma tissue and sclerenchyma tissue
Parenchymathin walls& large vacuole;store sugar and starch
Collenchyma supports herbaceous(non-woody) plants
Sclerenchyma have cell wall thickened by lignin;give support & mechanical strength to mature regions of a plant
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Collenchyma cells
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3. Vascular tissueConsists of xylem & phloemXylem transport water and mineral salts
to all part of the plantPhloem transport food(organic)
substances to all parts of the plant
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Organs and systems in plant
Organs root,stem, leaf and flowerFlowering plants have 2 systems:(a) Root system consists of all root of the
plant(b) Shoot system consists of stem, leaves,
buds, flowers and fruits
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Regulating the internal environment
What is internal environment?- Refers to the environment inside an
organism, which is the fluid(blood plasma and interstitial fluid) surrounding the cells
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The necessity for maintaining an optimal internal environment
The physical factors and chemical factors of the internal environment must be maintained for the cells to function optimally
Physical factor includes: temperature, blood pressure & osmotic pressure
Chemical factors: salt&sugar content, PH value
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Homeostasis
Is the maintenance of a relatively constant internal environment for the cells to function optimally
Any increase in the value of a physical or chemical factor will trigger the homeostatic mechanism to bring it back to normal
Any decrease will trigger the homeostatic mechanism to raise it back to normal
The mechanism that governs homeostasis is called the negative feedback mechanism
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The involvement of various systems in maintaining an optimal internal environment
Systems in the body function interact with one another to maintain a stable internal environment
For example: body temperature, concentration of oxygen & carbon dioxide, the blood glucose level, blood osmotic pressure, chemicals contents and PH level
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Body temperatureIs regulated by the integumentary system(skin and sweat
glands), nervous system, circulatory system, muscular system and endocrine system
Body temperature RISES
The receptors in the skin detect the changes
Information is transmitted to the hypothalamus(temperature regulatory centre in the brain)
activates
activatesBlood
vessels
Sweat gland
Dilate and allow more blood to flow near the surface of the body
Increase heat loss to the external environment
Produces more sweat that will lower the body temperature
Increase heat loss through evaporation
Body temperatur
e is restored to
normal
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2.3 Appreciating the uniqueness of the cell
The state of certain cells without a particular cellular components
Organelle missing
Predicted state of the cell
Nucleus • All cell activities stop• Cell does not live for long• The cell dies
Mitochondrion • No energy for cell activities• The cell dies
Ribosome • Cell is unable to synthesis enzymes (proteins)• Cell growth stops• Cell is unable to repair itself• Finally, the cell dies
Endoplasmic reticulum
• Less enzymes produced• Synthesis and transport of proteins and glycerol stop
Golgi Body • Proteins produced become defective• Cell is unable to produce certain types of protein
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Most of cells are specialised for the function that they perform
1. Muscle cells - Cell is able to contract
Specialised function produces movement
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2. Neurone- Shaped into a long thin fibre
Specialised function conducts nerve impulses
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3. White blood cell- Changes its shape
Specialised function Engulf and destroys microorganisms by phagocytosis
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4. Red blood cell- Disc shape, biconcave and without nucleus
Specialised function Transports oxygen (its nucleus is absent so that there is more room to transport oxygen)
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Exercises1. How does an amoeba feed, move, reproduce, respond
to stimulus, grow, excrete waste, and rid its body of excess water?
2. What are the problems of a multicellular organisms?3. What advantages does a cockroach have over an
amoeba?4. What is internal environment?5. What are the four factors controlling the internal
environment?6. What human body systems regulate:(a) Body temperature(b) Osmotic pressure(c) Blood glucose level(d) pH of the plasma