L eucoplasts (White plastids)
They are colourless plastids which don't contain
any pigments.
Function: They store starch.
They exist in cells of:-
1- Inner cauliflower leaves
2- Potato roots
Fig. (17) Leucoplasts
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Chromoplasts (Coloured plastids)
They contain pigments called Carotenoids,
their colours may be red, orange or yellow.
They exist in cells of:-
1- Petals of flowers and fruits.
2- Roots of some plants such as radish
Fig. (17) Chromoplasts
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Chloroplasts (Green plastids)
They contain chlorophyll pigment
which change the light energy of sun to
chemical energy stored in glucose
chemical bonds
They exist in the cells of:
Green leaves and stems of plants.
Structure:-
A chloroplast consists of :-
1- Inner membrane Fig. (18) Structure of a chloroplast
2- Outer membrane
3- Stroma: An inner filling surrounded by the bi-layer membrane
4- Granum: Stacks of inner membranes in the form of disks.
Living organisms are classified according to their cells structure into:-
Prokaryotic cells: Such as bacteria
Eukaryotic cells: Such as Monera, protista, fungi, plants and animals
Common properties between prokaryotic and eukaryotic cells
1- They are surrounded by cell membranes which separate between their internal structures and their external mediums.
2- They both have cell organelles that allow cell carry out its vital processes.
3- They have cytoplasm in which cell organelles are suspended, it has substances which are essential for cell such as water, salts and enzymes.
4- They have the hereditary material essential for their reproduction which control all the processes within cells.
Prokaryotic cells
1- They are much smaller than eukaryotic cells
2- Their structures are less complex
3- They don't have any nuclei, as their hereditary material exist in cytoplasm directly
4- They don't have many organelles as eukaryotic cells. However, they can perform all cellular activities (nutrition, respiration, movement, reproduction, responding to environment…etc)
Eukaryotic cells
1- They are bigger than prokaryotic cells
2- They have complex internal structure
3- Their hereditary material are surrounded by nuclear membrane (they have nuclei)
4- They have many organelles
.
Fig. (20) Comparison between eukaryotic and prokaryotic cells
Cell wall: A wall made of cellulose which surrounds the cell membranes of plant cells and gives them definite shapes.
Cell membrane: A thin membrane which surrounds all cells, it consists of phospholipid bi-layer and allows the passage of substances to and from the cell.
Nucleus: The largest and most obvious organelle in eukaryotic cells which carries chromosomes which are responsible for transferring hereditary traits to the offspring.
Cytoplasm: A jelly-like fluid filling the space between the nucleus and cell membrane which consists of water, inorganic and organic compounds.
Ribosomes: Spherical organelles which occur in cytoplasm or endoplasmic reticulum of cells, they play an important role in protein synthesis process.
Centrosome: An organelle in animal cells which consists of two centrioles, it plays and important role in cell division process.
Endoplasmic reticulum: A group of membranous tubes which spread across the cell and connected with both cell and nuclear membranes, it plays an important role in transporting substances around the cell.
Golgi body: A flat membranous sac-like organelle which receives the substances transported by endoplasmic reticulum and distribute them across cell parts.
Lysosome: A small spherical membranous organelle which plays an important role in digesting nutrients and getting rid of wastes.
Mitochondria: An organelle inside living cells which plays an important role in generating energy.
Vacuoles: Membranous sacs inside cells which store water, nutrients and wastes
Plastids: Membranous organelles which occur in plant cells.
Leucoplasts: They are colourless plastids which don't contain any pigments.
Chromoplasts: They are coloured plastids which contain coloured pigments called carotenoids.
Chloroplasts: They are green plastids which contain green pigment called chlorophyll, they play an important role in photosynthesis process.
Prokaryote: A Cell whose hereditary material is not surrounded by a nuclear membrane and don't have many cell organelles such (ex. Bacteria)
Eukaryote: A Cell whose hereditary material is surrounded by a nuclear membrane and has many cell organelles.
1- Plant cells have definite shapes
Because they are surrounded by cell walls made of cellulose which give plant cells their definite shapes
2- Cell membrane is in liquid state
Because the phospholipids forming it are in liquid state
3- Cell membrane is cohesive
Because there are cholesterol molecules bound to phospholipid ones, which makes the membrane cohesive
4- The importance of nuclear membrane in nucleus
Because it separates between the nucleus components and cytoplasm
5- Plasma membrane plays an important role in cell
Because it identifies the substances entering cells and allow their passage from and to them.
6- Nucleus is the most important organelle in cell
Because:-
1- It controls all processes occurring in cell
2- It contains chromosomes which contain genes (hereditary material)
3- It controls cell divison process
4- It contains the nucleolus responsible for the formation of ribosomes which synthesize proteins.
7- Ribosome plays an important role in cell
Because it synthesizes proteins in cell
8- The importance of ribosomes which exist in cytoplasm
Because they synthesize proteins and send them to all cell parts to be used in vital processes like growth.
9- The importance of ribosomes which exist in endoplasmic reticulum
Because they synthesize proteins which the inner endoplasmic reticulum send out of the cell in the form of secretions
10- Centrosome plays an important role in animal cells.
Because it plays an important role in cell division process, as its centrioles migrate towards the two poles of cell forming spindle fibres. It also forms cilia and flagella which helps the cell move.
11- The importance of the smooth endoplasmic reticulum
Because it synthesizes lipids, changes carbohydrates into glycogen, and make some toxics less poisonous
12- The importance of rough endoplasmic reticulum
Because it contains a great number of ribosomes to synthesize proteins and modifies them, too.
13- Chromosome are called by this name
Because they contain basic dyes that colour them , as the word chromosomes is derived from Latin language and means "colour body"
14- Golgi bodies are called by this name
To honour scientist "Camillo Golgi" who discovered them in 1898.
15- Golgi bodies play an important role in cells
Because they receive substances produced by ER and transport them across the cell or expel them out of it in the form of secretions.
16- The importance of Lysosomes in cells.
Because they get rid of old and destroyed organelles or cells, and contain digestive enzyme that digest nutrient inside cells.
17- The importance of Lysosomes in white blood cells
Because they destroy microbes
18- Cell is not affected by the digestive enzymes of Lysosomes
Because Lysosomes are surrounded by membranes.
19- Mitochondria have folds in their inner membranes called Cristae
In order to increase the surface area on which chemical reactions occur to speed them up
20- The biological importance of Mitochondria inside living cells
Because they store respiratory enzymes, substances which contain stored energy, and the energy resulted from respiration in the form of a compound called Adenosine Triphosphate (ATP)
21- Most cells have vacuoles
To store water ,nutrients and wastes
21- Plant cells can perform photosynthesis process, while animal cells cannot
Because plant cells have chloroplasts containing chlorophyll, which change light energy of sun into chemical energy and store it in glucose chemical bonds, while animal cells do not have these chloroplasts.
22- Bacteria are prokaryotes
Because their hereditary materials are not surrounded by nuclear membranes but exist in cytoplasm, and they do not have many cellular organelles
23- Human cells are eukaryotic cells
Because their hereditary material are surrounded by nuclear membranes, and they contain many cellular organisms.
24- There are many Golgi bodies in glandular cells
Because Golgi bodies in these cells are responsible for secreting hormones.
1- Plant cells were not surrounded by cell walls.
They would not have definite shapes
2- Cell walls didn't have any pores (holes)
Water and dissolved substances would not be able to enter plant cells.
3- Nuclei of eukaryotes did not have any nuclear membranes surrounding them.
The components of nucleus would mix with cytoplasm
4- Cells didn't have ribosomes
Cells wouldn't be able to synthesize proteins
5- Animal cells didn't have centrosome
They wouldn't be able to divide into two cells, as the two centrioles of centrosome form spindle fibres across the cell during cell division process (which help the cell divide into two cells)
6- Cells lack endoplasmic reticulum
Substances won't be transported across and outside the cell.
7- Cells didn't have smooth endoplasmic reticulum
They wouldn't be able to synthesize lipids or form new membranes for cellular organelles.
8- Cells didn't have Golgi bodies
Substances wouldn't be transported from the endoplasmic reticulum to other parts of cell.
9- White blood cells didn't have Lysosomes
They wouldn't be able to destroy microbes
10- Living cells didn't have Lysosomes
They wouldn't be able to digest nutrients or get rid of wastes.
11- Lysosomes of cells are not surrounded by membranes
The digestive enzymes inside the cell would spread in cytoplasm which may harm it.
12- Cells didn't have mitochondria
They will not be able to store energy or respiration enzymes.
13- Plant cells didn't have chloroplasts
They will not be able to perform photosynthesis process
1- Choose the correct answer
1- Cell wall is formed from ………. organic compound
A- Lipids B- Glucose C- Phosphoproteins D- Cellulose
2- Cell membrane is composed of ……..
A- Phospholipids bi-layer
B- Cellulose layer
C- Chitin bi-layer
D- Glycoprotein bi-layer
3- ……. are responsible for protein synthesis process in living cells.
A- Mitochondria B- Lysosomes C- Cytoskeleton D- Ribosomes
4- Centrosome exists in all animal cell except for…..
A- Nerve cells B- Sperm cells C- Liver cells D- Muscle cells
5- Chromosomes are formed in ……. Stage of cell division
A- Anaphase B- Metaphase C- Telophase D- Prophase
6- …….. form cilia and flagella in animal cells
A- Centrosome B- Mitochondria C- Lysosome D- Ribosome
7- ………. is responsible for generating energy in cell
A- Centrosome B- Mitochondria C- Lysosome D- Ribosome
8- ……….is responsible for digesting nutrients in cell.
A- Centrosome B- Mitochondria C- Lysosomes D- Ribosomes
9-……. are plastids which are devoid of pigments
A- Leucoplasts B- Chromoplasts C- Chloroplasts D- Chromatin
10- All the following organelles exist in animal cells except ……..
A- Cell wall B- Cell membrane C- Mitochondria D- Lysosomes
11 ………. cells do not have true nuclei.
A- Bacteria B- Monera C- Plants D- Animals
2-Write the scientific term
1- A cell that doesn't have a true nucleus and most cellular organelles
2- A cell which has a true nucleus and many cellular organelles.
3- A structure which is responsible for synthesizing proteins.
4- A structure which is responsible for synthesizing lipids.
5- A structure responsible for digesting nutrients
6- Pigments which exist in chromoplasts
7- A pigment which exist in chloroplasts
8- Thin filaments coiled around each other which turn into chromosomes during cell division process.
4- Compare between
1- Animal and plant cell
2- Prokaryote and eukaryote
5- This is the diagram of a typical plant cell, answer the following question
1- Label the previous cell
2- Mention the function of (A), (D) and (G)
3- Which organelle is responsible for synthesizing proteins?
6- This is the diagram of a typical anima cell, answer the following questions
1- Label the previous cell
2- Mention the function of (A), (I), (J)
3- Which organelle is responsible for synthesizing lipids in cell
1- Choose
1- Cellulose 2- Phospholipid bilayer 3- Ribosomes 4- Nerve cells
5- Metaphase 6- Centrosome 7- Mitochondria 8- Lysosomes 9- Leucoplasts
10- Cell wall 11- Bacteria
2- Write the scientific term
1- Prokaryote 2- Eukaryote 3- Ribosomes 4- smooth endoplasmic reticulum
5- Lysosomes 6- Carotenoids 7- Chlorophyll
3- Compare between
1- Animal and plant cells
Plant cell |
Animal cell |
- It doesn't have centrosome, but has a part of cytoplasm which form spindle fibres in cell division process
- Cell wall made of cellulose surrounds the plasma membrane |
- It has a centrosome whose two centrioles form spindle fibers in cell division process
- It is surrounded by plasma membrane
|
2- Prokaryote and eukaryote cells
Eukaryotic cells |
Prokaryotic cells |
- They are more complex cells
- Their hereditary materials are not surrounded by nuclear membranes
- They contain many cellular organelles
(ex. Animals) |
- They are less complex cells
- Their hereditary materials are not surrounded by nuclear membranes.
- They lack many cellular organelles.
(ex. Bacteria) |
5- Plant cell
1- Label
A- Golgi body B- Vacuole C- Mitochondria D- Ribosomes E- Cell wall
F- Cell membrane G- Chloroplast H- Rough endoplasmic reticulum
I- Nucleolus J- Nucleus K- Cytoplasm
2- Function
(A) Golgi bodies: It modifies and transports the substances sent to them from the ER across the cell or outside it.
(D) Ribosomes: They synthesize proteins.
(G) Chloroplast: Perform photosynthesis process.
3- (D) ribosomes
6- Animal cell
1- Label
A- Mitochondria B- Golgi body C- Cytoplasm D- Nucleolus E- Nucleus
F- Nucleus G- Plasma membrane H- Rough endoplasmic reticulum
I- Centriole J- Smooth endoplasmic reticulum K- Vacuole L- Ribosome
2- Function
(A) Mitochondria: Stores and generates energy.
(I) Centiole: forms spindle fibres across the cell during cell division process.
(J) Smooth ER: Changes carbohydrates to glycogen – synthesize lipids
3- Smooth endoplasmic reticulum