5090 Biology - Unit 1 Cell Structure and Organisation
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Course
Cambridge O Level
Institution
Cambridge O Level
Complete note covering all aspects required for Cambridge O Levels Biology, Unit 1 Cell Structure and Organization. Includes detailed explanations, clear tables and diagrams to help you ace your exams.
I myself as a student who got an A* for my Cambridge O Level Biology can guarantee that these no...
Cell-is the smallest structural and functional unit of life. Each type with its own functions like RBC
transport oxygen and Neurons (Nerve Cells) transmit nerve impulses.
All living things have cells. Animals-Animal Cells and Plants-Plant Cells.
Unicellular organisms-one celled organisms (ex:- Amoeba, Paramecium, Yeast)
Multicellular organisms-many cells (ex:-most visible living things)
Cells are observed using a microscope (light and electron). And would look like below diagram
when observed through a light microscope.
Part of the cell Features Functions
Cell Wall Only in plant cells, made of cellulose (forms a Maintains the shape of the
crisscross fibres) and is a fully permeable cell, maintains turgidity,
membrane. prevents the cell from
bursting when taking in
water.
Cell membrane Is a very thin layer of fat and protein, Enclose the cell, only
semi/selectively/partially permeable membrane. some elements can enter
(not all).
Cytoplasm Clear jelly like structure, containing 70% water, Holds the cell organelles,
metabolic reactions take place, organelles are carry out different
submerged in it. metabolic reactions.
Vacuoles Plant cells have large vacuoles containing ‘Cell To maintain the water
Sap’, surrounded by a membrane called balance and to keep the
‘Tonoplast’. cell firm.
Animal cells have a small space called ‘Vesicle’.
, Chloroplast In plant cells, have green pigments called Photosynthesis
Chlorophyll, photosynthesis takes place and
contains starch grains.
Nucleus Main organelle in a cell and is surrounded by the Transfer inherited
Nuclear Envelope, has Chromatin Body that characteristics from
contains the DNA (Deoxyribo Nucleic Acid), generation to generation.
during cell division (Mitosis) it to divides and
forms Chromosomes, controls the type and Controlling cell activities.
quantity of enzymes produced, regulates chemical
changes, and determines the role of a cell.
Mitochondria Oval/rod shaped structure, powerhouse of the cell, Cellular respiration
invisible to light microscope, more mitochondria is (Aerobic Respiration)
present in places which need more energy. takes place here.
(Prokaryote doesn’t have this)
Ribosome Small organelle that can be seen close to the Producing proteins
Endoplasmic Reticulum or scattered freely. It’s (Protein synthesis)
made of RNA and Proteins.
Turgidity - the internal pressure in a plant cell when water is absorbed and the cell wall acting like a
balloon. This keeps the plant stem firm and upright and its leaves flat.
Difference between Animal and Plant Cells
Plant Cell Animal Cell
Has a cell wall of Cellulose outside the Cell No Cell wall
Membrane.
Has a cell membrane, nucleus, and Has a cell membrane, nucleus, and
cytoplasm cytoplasm.
Has Chloroplasts containing Chlorophyll No Chloroplast or Chlorophyll.
Has large vacuoles containing Cell Sap. Have small or no vacuoles.
Might have starch grains. No starch but might contain Glycogen
granules.
Often regular in shape Irregular in shape
Around 40-100 μm in diameter. Around 10-20 μm in diameter.
Specialization of Cells
Most cells (after division) become specialized, so that;
They do one particular job
They develop a distinct shape
Special kinds of chemical reactions take place in their cytoplasm
This specialization of cells is also referred to as ‘Division of Labour’.
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