A-Level生物学练习（第1章、细胞结构和组织 Cell Structure and Organisation）

本章封面：

Work Example:

Checkpoint:

Answer: B. Cell
Explanation: A cell is the basic unit of life as it is the simplest unit which makes up a living thing.

Answer(s): Chloroplast; Mitochondrion; Nucleus; Ribosome.
Explanation(s):
(1). Chloroplast is the site for photosynthesis (aka process by which plants make food).
(2). Mitochondrion provides energy for cell activities like growth and reproduction.
(3). Nucleus controls cell activities such as growth and repair, and is important for cell division.
(4). Ribosomes synthesize proteins in the cell.

Answer: Differences between plant cells and animal cells:

(1). Cell walls are absent in animal cells but present in plant cells;
(2). Chloroplasts are absent in animal cells but present in plant cells;
(3). Vacuoles in animal cells are small and many, but there is only one large and central vacuole in plant cells.

Reference:

Test Station:

Answer: A. Cell
Explanation: A cell is the basic unit of life as it is the simplest unit which makes up a living thing.

Answer: A. Tissue
Explanation: A group of similar cells working together to perform a specific function is called a tissue.

Answer(s):
( a ). First type of ribosomes exist freely throughout the cytoplasm; Second type of ribosomes are attached to organelles in the cell.
( b ). Both types of ribosomes synthesize proteins in the cell.
( c ). These cells certainly have many ribosomes, since the function of ribosomes is to synthesize protein.

Explanation(s):
( a ). Ribosomes are found freely throughout the cytoplasm or attached to organelles in the cell.

Answer(s):
( a ). 1st feature: this organism has a visible cell membrane; 2nd feature: this organism has green pigment attached to its inner organelles.
( b ). 1st reason: there is no visible vacuole in this organism; 2nd reason: there is no visible chloroplast in this organism.
( c ). Possible way of obtaining energy: the green pigment is chlorophyll and therefore it obtains energy via photosynthesis.

Explanation:
( c ). Chloroplast contains a green pigment called chlorophyll which is contained in stacks of membranes.

Answer(s):
( a ). Differentiation is the process where cells develop special structures or lose certain structures to enable them to carry out specific functions.
( b ). Root hair cells have a long and narrow root hair extension, which increases surface area-to-volume ratio of the cell which increases the rate of absorption of water and mineral salts.
( c ). Firstly, red blood cells have a circular and biconcave shape which increases the rate of oxygen diffusion; Secondly, nucleus is absent in red blood cells, which increases amount of haemoglobin carried.