CHAPTER 2 : CELL STRUCTURE &

CELL ORGANISATION

2.1 Cell Structure & Function2.2 Cell Organisation

2.1 CELL STRUCTURE & FUNCTION

Learning Outcomes :1. Draw & label an animal cell and a plant

cell2. Identify the cellular components of an

animal cell & a plant cell3. State the functions of the cellular

components in an animal and a plant cell4. Compare & contrast an animal cell with a

plant cell5. Relate the density of certain organelles

with the functions of specific cells.

HISTORY Robert Hooke (1665) was first

discovered the cell structure of plant

He examined fine slices of cork with a primitive microscope

He saw many ‘box-like’ structures , then he called ‘cells’, from Latin for ‘little rooms’.

THE CELL THEORY(Schleiden M & Schwann T)

All living organisms are made up of one or more cells

New cells are formed by the division of pre-existing cells

Cells contain genetic material of an organism which is passed from the parent cells to daughter cells

Cells are the basic unit of structure & function in living things

ORGANELLES specialised structures which are each surrounded by its own membrane & perform specific function

PLASMA MEMBRANE

Thin, semi-permeable Made of protein, lipid Controls the

movement of substances in and out of the cell

Non-organelle

CYTOPLASM Jelly-like substance

that contains water & mineral salts

Contains organelles and food such as carbohydrates (glucose)

Medium for metabolic reactions

Supplies the substances required by organelles

Non-organelle

CELL WALL Thick layer outside

the plasma membrane Made up of cellulose,

fully permeable Maintains the shape

of the plant cells Provides mechanical

support Non-organelle

NUCLEUS Spherical shape with

double membrane Contains nucleolus,

chromosomes, nucleoplasm & nuclear membrane

Controls & regulates all the activities of cell

Contain the heredity factors responsible for the traits

RIBOSOME Small particles

consisting of RNA Exists freely in the

cytoplasm or on the surface of the endoplasmic reticulum

Synthesis of protein

ENDOPLASMIC RETICULUM A system of membrane-

enclosed tubules closely packed together and continuous with the nuclear membrane

RER has ribosome, SER does not have

Transport system for protein & lipids within the cell

RER transport protein to other part of cell

SER stimulates the synthesis of lipids & cholesterol & transport within the cell

GOLGI APPARATUS Vacuolar region

surrounded by a complex meshwork of vesicles budding off at its end

Received protein & lipids from ER & modify them to form specific secretion such as enzymes & hormones

Pack the secretions formed into secreting vesicles & transport them to plasma membrane to be secreted

Controls the secretory activity of cells

Formation of lysosomes

VACUOLE Filled with cell sap,

surrounded by semi-permeable membrane called the tonoplast

Contain water, sugar & dissolved minerals

Maintain turgidity of cells in plants

MITOCHONDRIA Rod-shape with a

double membrane Outer membrane is

smooth, inner membrane is folded to form cristae

Known as ‘power-house’ of the cell

Releases energy as it is the site for aerobic respiration

CHLOROPLAST Disc-shape organelle

with a double membrane

Consist of an orderly arrangement of grana within the stroma. Granum contains chlorophyll

Site of photosynthesis Trapped light energy

and change it into chemical energy

LYSOSOMES Membrane-bound

vesicles found in animal cells

Contain enzymes which control breakdown of protein & lipids

Contain enzymes that digest aged or defective cell components or materials taken in by the cell from its environments such as food particles or bacteria.

CENTRIOLES A pair of small

cylindrical structures (microtubules)

Form spindle fibre for cell division

COMPARE & CONTRAST

ANIMAL CELL SIMILARITIES PLANT CELL

A plasma membrane surrounding the cytoplasm

Both contain nucleus & cytoplasm

Both contain organelles such as mitochondria, ER, Golgi apparatus &

ribosomes

ANIMAL CELL DIFFERENCES PLANT CELLSmaller than plant

cellSIZE Larger than animal

cellIrregular shape SHAPE Often regular in

shapeAbsent CELL WALL PresentAbsent CHLOROPLAST Present

No large vacuoles. If present, small &

numerous.

VACUOLES Large central vacuole filled with

cell sapIn a form of glycogen

in liver & muscle tissues

FOOD STORAGE In a form of starch

Present CENTRIOLES AbsentSome animal cell

have cilia or flagellaCILIA & FLAGELLA Absent

RELATIONSHIP BETWEEN THE STRUCTURE OF AN ANIMAL CELL

& A PLANT CELL

The number of specific organelles in a cell varies on the type of cell and its function.

Active cell many mitochondria to provide enough energy for its activities. Eg. : sperm cells, flight muscle cell (insects & birds)

Cell in meristems of plant shoot & root

Green plants more chloroplasts to carry out photosynthesis such as palisade mesophyll cells and spongy mesophyll cells, also guard cells.

EXERCISE 2.11. What are the organelle structures of a

cell?

2. What are the functions of each structure describe above?