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Grade 7 – Science Revision – Q2 “ Model Answer”
Lesson 1: Cell Structure and Functions + Levels of Cellular Organization
Section 1: Define:
1. Cell: The smallest structural and functional unit of all living organisms.
2. Organism: is any living thing that carries out its own life processes.
3. Unicellular: Organisms made up of just one cell.
4. Multicellular: Organisms made up of more than one cell.
5. Cell membrane: a protective layer that covers a cell’s surface and controls materials moving into
and out of the cell.
6. Cytoplasm: is the region inside the cell that includes the fluid and all the organelles.
7. Nucleus: membrane-bound organelle that contains DNA.
8. Ribosome: They are organelles without cell membranes which are important to produce proteins.
9. Prokaryote: are single-celled organisms that do not have a nucleus or membrane-bound organelles.
10. Eukaryote: are organisms made up of cells that contain DNA in a nucleus, membrane-bound
organelles, and ribosomes.
11. Flagella: hair like structures (tail) that help the cell move.
12. Cytoskeleton: network of protein filaments that give shape and support to cells.
13. Tissue: Made of cells that work together to perform a specific function.
14. Organ: Made of different types of tissues
15. Organ system: made of different organs.
Section 2 : Draw and label a prokaryotic cell:
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Section 3: Short answers:
1)
1)
2)
3)
4)
1)
2)
State the cell theory?
All organisms are made up of one or more cells.
The cell is the basic unit of all organisms.
All cells come from existing cells.
What are the 5 common features of all cells?
Cytoplasm
3) Ribosomes.
Cytoskeleton
5) Cell membrane
4) DNA
Section 4: Match:
Scientist
Robert Hooke
Contributions
Schwann
He concluded that all animals are made up of cells.
Virchow
He stated that all cells come from pre-existing cells.
Anton van Leeuwenhoek
The first scientist who observed living cells.
Schleiden
He concluded that all plant tissue are made up of cells.
The first scientist to observe cells and name them.
Lesson 2 : The Chemistry of life.
Section 1: Define:
1. Atom: The smallest unit of an element that maintains the properties of that element
2. Element: a substance that cannot be broken down into a simpler substance.
3. Compound: is a substance made up of atoms of two or more elements joined by chemical bonds.
4. Simple carbohydrates: are made of one or a few sugars linked together.
5. Complex carbohydrates: _contain many sugar molecules linked together.
6. Hydrophilic: Substances that attract water.
7. Hydrophobic: Substances that repel water.
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Section 2 : Label the following:
2) Ribose sugar
1) Phosphate
3) Nitrogen base
Hydrophilic phosphate head
Phospholipid
Hydrophobic lipid tail
Section 3 : Complete the table:
Macromolecule:
Lipids
Subunit:
Fat molecules
Function:
1- Insulate
organs.
2. Form our cell
membrane.
3. Store energy
Carbohydrate
Glucose
Food types:
Vegetables, bread,
pasta & chocolate
Examples:
1- Oil
2- Wax
3- Phospholipid
Main source
of energy
Proteins
Amino Acid
1- Build and repair
body structures.
2- Proteins called
enzymes speed up
chemical reactions
Nucleic acids
Nucleotide
Carries our
genetic
information
that cells need
to make other
molecules.
Fish, meat and chicken
Simple and
complex
DNA & RNA
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Lesson 3: Homeostasis & Cellular Respiration.
Section 1: Define:
1. Homeostasis: is the maintenance of a constant internal state in a changing environment.
2. Photosynthesis: is a process by which the plants store the energy from the sun into sugar.
3. Cellular respiration: is a process by which Plants & animals use oxygen to produce energy from
food.
4. Semi permeable: allow only certain particles to move into or out of the cell.
5. Diffusion: is the movement of molecules from high concentrations to low concentrations.
6. Osmosis: is the diffusion of water through a semi-permeable membrane.
7. Facilitated diffusion: is the movement molecule in and out of cells through protein channels.
8. Passive transport: Is the movement of particles with a concentration gradient and uses no energy.
9. Active transport: Is the movement of particles against a concentration gradient and requires energy
10. Hypertonic solution: Low levels of water and high concentration of salt
11. Hypotonic solution: Low concentration of salt and high levels of water
12. Endocytosis: is a process by which a cell uses energy to surround a particle to bring it into the cell.
13. Exocytosis: is a process by which particles are released from the cell using energy.
Section 2: Compare:
Cellular Respiration
Photosynthesis
Location:
Reactant:
Mitochondria
Glucose and water
Product:
Energy:
(Stored/produced)
Carbon dioxide and water
Is produced from food
Chloroplast
Carbon dioxide and
water
Glucose and water
Is stored in food.
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What happens to
Cells if placed in:
Hypertonic solution
Isotonic solution
Hypotonic solution
The cell will lose
water and shrink
Nothing
The cell will take
in water, swell
and burst.
Section 3 : Label the following:
The reactants are:
Carbon dioxide and water
The products are:
Glucose and water
Lesson 4 : Bacteria & Viruses.
Section 1: Define:
1. Microorganism: an organism which is too small to be seen by the naked human eye.
2. Pathogen: Bacteria, virus, or other microorganism that can cause disease.
3. Host: a living thing a microorganism uses as food or shelter.
4. Microbial infection: Infection is the invasion of body tissues by a microorganism (pathogen),
usually causing disease.
5. Bacteria: Unicellular prokaryotic cell with no nucleus.
6. Virus: Are Non- Living as they do not possess any of the characteristics of living organisms
7. Binary fission: the asexual reproduction of bacteria, where the cell divides into 2 identical daughter
cells.
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8. Lytic cycle: The viral cycle where the virus takes over the cell, reproduces new viruses, and
destroys the cell
9. Lysogenic cycle: the viral cycle in which the viral DNA integrates into the cell’s DNA and becomes
part of the host.
10. Provirus: When the viral DNA becomes a part of the host.
11. Bacteriophage: A virus that attacks bacteria.
Section 2: Complete the table:
Cocci bacteria:
Spirillum bacteria:
Bacillus bacteria:
Bacterial shape
Sphere shaped bacteria
Spiral shaped bacteria
Rod shaped bacteria
Draw
Section 3: Draw & Label A bacteriophage and then label the bacteria:
A: Pilli
B: Ribosomes
C: DNA
D: Flagella
E: Cell wall
B. Draw & Label the lytic cycle of a virus:
F: Cell membrane
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Section 4: Short Answers:
1) How does the body fight off infection?
a. By a rise in TEMPERATURE.
b. Production of ANTIBODIES by white blood cells.
2) What are the methods of prophylaxis against infection?
a. Vaccination,
b. Disinfection,
c. General & personal hygiene.
3) Modes of disease transmission?
1- Air (Coughing and sneezing).
2- Direct contact (blood, saliva or semen).
3- Contaminated food, and water.
4- Contact with infected creatures (vector),
4) Is the virus living or non-living? Why?
- They do not possess any of the characteristics of living organisms (except when found
inside a host they Reproduce).
Lesson 5 : Mitosis & cell cycle.
Section 1: Define:
1. Chromatin: DNA is found in a mass of loose strands
2. Chromatid: When the chromatin coils around the protein.
3. Chromosome: 2 sister chromatids attached by a centromere.
4. Centromere: The structure that holds the 2 sister chromatids together.
5. Interphase: is the stage in the cell cycle during which the cell is not dividing.
6. Mitosis: the part of the cell cycle during which the nucleus divides.
7. Cytokinesis: is the division of the parent cell’s cytoplasm to form 2 new cells.
Section 2: State the phase:
Cytokinesis
Anaphase
1. What phase are daughter cells in as a result of mitosis?
2. During what phase of mitosis do centromeres divide and the chromosomes move toward their
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respective poles?
Prophase
3. What is the phase where chromatin condenses to form chromosomes?
Centromere
Chromatid
4. What is the name of the structure that connects the two chromatids?
5. In a chromosome pair connected by a centromere, what is each individual chromosome called?
Cytokinesis 6.
When do cytoplasms divide ?
Prophase I 7.
When do crossing over occur ?
Metaphase
8. Which phase of mitosis is the last phase that chromatids are together?
Interphase 9.
Which phase of the cell cycle is characterized by a non-dividing cell?
Interphase 10.
The period of cell growth and development between mitotic divisions?
The diagram below shows size cells in various phases of the cell cycle. Note the cells are not
arranged in the order in which the cell cycle occurs.
____________________1.
Which cell is in metaphase? C
____________________2.
Which cell is in the first phase of M phase (mitosis)? A
____________________3.
In cell A, what structure is labeled X? Centriole
____________________4.
List the diagrams in order from first to last in the cell cycle. DACEB
____________________5.
Which cell is in anaphase? E
Lesson 6: Meiosis
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Section 1: Define:
1. Haploid: Cells with 1 set of chromosomes.
2. Diploid: Cells with 2 sets of chromosomes.
3. Sex chromosome: One chromosome pair which control the development of sexual characteristics.
4. Meiosis: the type of cell division that produces haploid sex cells such as sperm or egg cells.
5. Crossing over: The exchange of genetic material between the homologous chromosomes
6. Homologous chromosome: chromosomes are found in pairs of homologous chromosomes, which
have the same structure and size and carry the same genes but different versions.
7. Fertilization: When sperm and ova join to form a zygote.
B. State the phase:
1.
Metaphase I
:
2.
Interphase
: DNA replication occurs
3.
Telophase II
: daughter cells divide forming 4 haploid cells
4.
Anaphase II
: sister chromatids separate
5.
Metaphase I
: spindle fibers attach to centromeres of tetrads
6.
Telophase I
: two daughter cells are created
7.
Metaphase I
: chromosomes move to opposite poles
8.
Metaphase I
:
homologous pairs separate.
9.
Metaphase II
:
chromosomes line up in the middle of the cell.
:
centromere splits.
10. Anaphase
II
tetrads line up at the equator
Section 2: Compare:
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What happens in the
cell?
Anaphase I
The homologous chromosomes
separate from their partners and
move to opposite ends.
Anaphase II
The sister chromatids separate from
their partners and move to opposite
ends.
Centromere intact
Centromere splits
.
Draw
What happens in the
cell?
Draw
Metaphase I
The homologous chromosome pairs
line up in the middle of the cell.
Metaphase II
The chromosomes line up in the
middle of the cell.
Section 3: Fill in the diagram
1.
2.
3.
4.
5.
6.
7.
8.
Anaphase I
Anaphase II
Prophase I
Metaphase I
Metaphase II
Telophase I
Prophase II
Telophase II & cytokinesis.
Good-luck 
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