F4- Biology- Chapter 2.1- Cell Structure and Function

Summary of descriptions and functions of cellular structures

Cellular Component	Descriptions & Functions
Plasma Membrane	- made of protein and phospholipids - semi permeable = selective barrier Function: regulate movement of substance in and out of cytoplasm
Cell Wall	- permeable to all fluids ( has tiny pores) Function: 1. gives shape 2. provide mechanical support 3. protect the plant cell from rupturing due to excessive intake of water
Cytoplasm	- contain organic and inorganic substances Function: 1. Acts as medium for biochemical reactions in the cell 2. Provide substances obtained from the external environment to the organelles.
Nucleus	Function of Nucleus: Controls all the activities which take place in the cell Consists of 1. Nuclear membrane 2. Nucleolus 3. Chromatin (the form that chromosomes take when the cell is not dividing, is contain within nucleoplasm 4. Chromosomes Function of Chromosomes: a. Carry genetic information which determines the characteristics and functions of a cell. b. contain coded information which regulate synthesis of protein
Vacuole	fluid filled sac surrounded by tonoplast (semi-permeable membrane) Cell sap fluid contained in a vacuole contains water, organic acid, sugar, amino acids, mineral salts, waste substances, pigments and metabolic by-products supports herbaceous plants so they do not wilt easily. Types of vacuole 1. Contractile vacuole : a. help to regulate water balance in these organisms. b. acts as a storage place in a cell 2. Food vacuole : storage pocket for food
Mitochondria	Function: release energy by going through process of cellular respiration (when food substances such as glucose are broken down with the help of enzymes present in mitochondria) - energy released stored in the form of ATP (adenosine triophosphates) that can be readily used by cells.
Ribosomes	attach to the surface of rough endoplasmic reticulum or suspended freely in cytoplasm  each ribosome consists 2 sub-units, 1 small 1 large, each of which comprises a type of ribonucleic acid (RNA) and protein.  place where synthesis of protein takes place  use information carried by the chromosomes to make these protein.
Endoplasmic Reticulum	Two types of endoplasmic reticulum: 1. Rough Endoplasmic Reticulum ( rough ER) has ribosomes attached to its surface transport proteins made by ribosomes protein departs from rough ER are enclosed in vesicles.  these protein can be transported from one cell to another 2. Smooth Endoplasmic Reticulum ( smooth ER) does not have ribosomes attached to its surface site of important metabolic reactions example: synthesis of lipids and detoxification of drugs and poison.
Golgi Apparatus	Function: processing, packaging and transporting centre of carbohydrates, proteins, phospholipids and glycoproteins.
Lysosomes	Function: contain hydrolytic enzymes  which digest or break down complex organic molecules such as protein, lipids, polysaccharides and nucleic acid eliminate worn out mitochondria and other damaged organelles to enable to renew itself fuse with food vacuole and dispense enzymes into these vacuoles to digest the contents of vacuole ( in cells of certain organisms) digest bacteria by breaking down the bacterial cell wall
Centrioles	- composed of a complex arrangement of microtublules - does not present in plant cell. Function: located just outside the cuclues from spindle fibres during cell division in animal cells
Chloroplasts	- contain green pigment chlorophyll  Function of chlorophyll in chloroplasts: traps sunlight and converts light energy into chemical energy during photosynthesis

Comparison of animal and plant cells

Similarities
have plasma membrane, cytoplasm, nuclues, endoplasmic reticulum, Golgi apparatus, ribosomes and mitochondria.
Differences
Animal cells	Aspect	Plant cell
Flexible	Shape	Fixed
Absent	Cell wall	Present
Absent	Chloroplast	Present
If present, are scattered throughhout the cell	Vacuole	Has one or few large vacuole(s)
Present	Lysosome	normally absent
Present	Centriole	absent

Relation between number of certain organelles with the functions of specific cells 

Types of cells	Function	Organelles found abudantly in the specific cells
Sperm cells	Require large amounts of energy to propel towards the uterus and Fallopian tube during fertilisation	Mitochondria
Flight muscle cells in insects and birds	Contract and relax to enable movements and flight	Mitochondria
Cells in the meristems	Divides actively	Mitochondria
Mesophyll palisade cells	Catch the energy from the sunlight for photosynthesis	Chloroplasts