1. Cell

Question 1

What does nucleus contain?

Answer 1

Contains hereditary material, DNA (in long thread-like structures called chromatin threads).
When the cell is dividing, the thin chromatin threads condense and become highly coiled chromosomes which
are visible under the light microscope.

Question 2

State 3 features of the nuclear membrane.

Answer 2

• Nuclear membrane or envelope surrounds the dense nucleoplasm.
• Nuclear membrane composed of two membranes, of which the outer membrane is continuous with the
  endoplasmic reticulum.
• Nuclear membrane perforated by numerous nuclear pores that control passage of substances moving in and
  out of the nucleus.

Question 3

State the function of nucleus.

Answer 3

Controls and directs activities such as cell growth, reproduction and repairing of cells.

Question 4

State 2 features of the cytoplasm.

Answer 4

Aqueous ground substance containing specialised structures called organelles.
Contain water (90%), essential ions such as sodiums, sugars and enzymes.

Question 5

State 2 features of nucleolus.

Answer 5

Sub-nuclear structure not surrounded by membrane and occupies about 1 /4 ot the volume of nucleus.
One or more nucleoli (singular: nucleolus) may be present within a nucleus.

Question 6

State the function of nucleolus.

Answer 6

Involved in protein synthesis.

Question 7

State the 3 features of cell membrane.

Answer 7

Selectively permeable, allowing smaller substances like water to pass through.
Made up of mainly proteins and lipids in the form of phospholipids.
Organic solvents such as alcohol penetrate membrane more rapidly than water.

Question 8

State the 2 functions of cell membrane.

Answer 8

Controls activities entering or leaving cell.

Act as receptor sites for recognising external stimuli and chemicals.

Question 9

State 2 features of mitochondrion.

Answer 9

Bounded by double membrane and are mostly spherical or rod-shaped.
Present in most cell and actual number depends on metabolic activity of cells. Highly active cells may possess up to 1000 mitochondria.

Question 10

State the function of mitochondrion.

Answer 10

Release energy in the form of adenosine triphosphate during cellular respiration for activities such as growth, cell division and active transport.

Question 11

State a feature of vacuoles.

Answer 11

Fluid-filled organelle surrounded by a selectively permeable membrane known as tonoplast (in plants)

Question 12

How does vacuole(s) differ in plants and animals?

Answer 12

In plant cells, a large central vacuole exist permanently. The plant vacuole cotains a liquid known as cell sap.
In animal cells, the vacuoles are smaller, numerous and often less permanent.

Question 13

State 2 functions of vacuoles.

Answer 13

Provide support for plants when it is filled with water by maintaining turgidity of cells.
Temporarily stores waste products and food reserves.

Question 14

State 4 features of chloroplast.

Answer 14

Bounded by double membrane and visible with a light microscope (3.0-10.0 um in diameter)
Chloroplast are found in green parts of plants and in algae
Chlorophyll is located in a series of membranes called thylakoids running through a matrix called stroma. In some parts, thylakoids may be stacked up to form granum.
May contain starch grains which are converted from glucose made during photosynthesis.

Question 15

State the function of chloroplast.

Answer 15

Contains pigment chlorophyll to trap/absorb sunlight during photosynthesis producing glucose.

Question 16

State 3 features of cell wall.

Answer 16

Made up of mainly cellulose.
Inelastic, inflexible and totally permeable.
May go through extensive lignification like xylem vessels.

Question 17

State 2 functions of cell wall.

Answer 17

Provide mechanical support.

Protects cells from overexpansions when water enters cell by osmosis , giving turgor pressure.

Question 18

State 3 features of ribosomes.

Answer 18

Made up of ribosomal RNA (ribonucleic acid) and proteins.
Can be found either in the cytoplasm or attached to the endoplasmic reticulum , forming rough ER.
Ribosomes on RER largely responsible for the synthesis of secretory protein as compared to free ribosomes synthesising intracellular proteins.

Question 19

State 2 features of ER.

Answer 19

A network of folded membrane forming sheets, tubes or flattened sacs called cisternae in cytoplasm.
Originates from outer membrane of nuclear membrane.

Question 20

State 2 features of rough ER.

Answer 20

Covered with ribosomes on the outer surface of the membrane.

Granular appearance due to ribosomes and more sheet-like.

Question 21

State the function of rough ER.

Answer 21

Transport proteins which are manufactured by ribosomes on its surface. These proteins are then exported out of the cell.

Question 22

State a feature of smooth ER.

Answer 22

Lacks ribosomes on its membrane and more tubular.

Question 23

State 3 function of smooth ER.

Answer 23

Synthesis of fats and steroids. Sex hormones in mammals are steroids.
Detoxification of harmful substances into harmless material.
Give rise to Golgi body.

Question 24

Where are rough ER commonly found?

Answer 24

enzyme secreting cell such as in the pancreas

Question 25

Where are smooth ER commonly found?

Answer 25

liver and skin oil glands

Question 26

State 4 features of Golgi apparatus.

Answer 26

Compact stack of membrane-bound sacs and associated vesicles called Golgi vesicles.
The sacs are fluid-filled and pinch off into smaller sacs called Golgi vesicles at their end.
Has a convex face formed by fusion of vesicles derived from ER and a concave face where vesicles are budded off.
Normally only one Golgi apparatus is found in each animal cell but many may be found in plant cells.

Question 27

State 2 function of Golgi apparatus.

Answer 27

Chemically modifies substances made by the ER.

Stores and packages these substances In vesicles for secretion out of the cell.

Question 28

State 2 features of lysosomes.

Answer 28

Spherical bodies bounded by a single membrane.

Contains hydrolytic enzymes and are abundant in secretory cell and phagocytes.

Question 29

State 3 functions of lysosomes.

Answer 29

Digestion of food and foreign particles such as bacteria.
Autophagy eg removal of unwanted structures worn-out organelles within the cell.
Autolysis eg self-destruction of a cell during metamorphosis.

Question 30

State the adaptation of root hair cell.

Answer 30

Has a long and narrow tail to increase surface area to volume ratio for absorption of water and mineral salts.

Question 31

State the 4 adaptation of human red blood cell.

Answer 31

Biconcave shape to increase surface area to volume ratio to increase the rate of oxygen transport.
Contain red pigment haemoglobin which binds to oxygen.
Lack nucleus so as to allow more haemoglobin to be packed in.
Flexible cell membrane to allow it to squeeze through tiny capillaries in order to supply oxygen to the tissue.

Question 32

State and describe the 3 ways xylem vessels can be lignified.

Answer 32

Annula -lignin deposited in rings
Spiral -spiral bands of lignin
pitted -with unlignitied pit while the rest are lignified.

Question 33

State 3 adaptation of xylem vessel.

Answer 33

Absence of cross walls and protoplasm to conduct water and mineral salts through the lumen easily without hindrance.
Lignified cell wall to strengthened wall and prevent collapse of individual xylem vessel.
Lignified xylem vessels when bundled together provide mechanical support to the plant.