Chapter 1: Cells

Question 1

What is a cell?

Answer 1

A cell is a unit of life. It consists of a mass of living matter called protoplasm

Question 2

Protoplasm

Answer 2

• a complex jelly-like substance
• made up of cell surface membrane, cytoplasm and nucleus
• where many chemical activities that ensure survival and growth of cell take place

Question 3

Cell surface membrane

Answer 3

• surrounds cytoplasm of cell
• made out of lipids and proteins
• a partially permeable membrane : only allowing some substances to pass through
• controls movement of substances in & out of the cell

Question 4

Cell Wall

Answer 4

• only present in plant cells (may be present in a few animal cells like bacteria)
• made out of cellulose
• protects the cell from injury and gives the plant cell a fixed shape
• fully permeable (does not control the type of substances that entre/leave the cell)

Question 5

Cytoplasm

Answer 5

• jelly-like substance that fills the inside of the cell and is enclose by cell surface membrane
• part of protoplasm between cell membrane and nucleus
• where most cell activities occur
• contains organelles which are cellular structures that performs a specific job within cell

Question 6

Parts of cytoplasm

Answer 6

1. Cell membrane
2. Smooth Endoplasmic Reticulum (SER)
3. Mitochondrion
4. Nucleus
5. Vacuole
6. Golgi Body
7. Vesicle
8. Rough Endoplasmic Reticulum (RER)
9. Ribosomes
10. Cytoplasm

Question 7

Nucleus

Answer 7

• surrounded by nuclear membrane
• contains genetic information in the form of chromosomes
• controls cell activities such as cell growth and the repair of worn-out parts
• essential for cell division
• w/o nucleus, cell are unable to divide

Question 8

Chromosomes

Answer 8

• long thread-like structure found in nucleus
• made up of proteins and deoxyribonucleic acid (DNA)
• DNA carries instructions that a cell needs for carrying our its activities
• when cell is dividing, chromosomes condense and shorten to become thick, rod-shaped structures

Question 9

Rough Endoplasmic Reticulum (RER)

Answer 9

• consist of a network of flattened spaces lined with a membrane
• surface is rough because of ribosomes that is attached to its surface
• outer surface of RER is continuous with nucleus membrane
• transports proteins made by ribosomes to the Golgi body for secretion out of the cell

Question 10

Ribosomes

Answer 10

• small round structures
• attached to RER or lie freely in cytoplasm
• needed to synthesise proteins in the cell
• ribosomes attached to the RER make proteins that are actually transported out of the cell
• ribosomes lying freely in the cytoplasm make proteins that are used within the cytoplasm of that cell

Question 11

Smooth Endoplasmic Reticulum (SER)

Answer 11

• does not have ribosomes attached to it
• more tubular than RER
• connected to RER
• synthesises substances such as fats and steroids
• converts harmful substances into harmless substances through detoxification

Question 12

Golgi Body (Golgi Apparatus)

Answer 12

• shaped like a disc
• consists of a stack of flattened spaces surrounded by membranes
• vesicles can be seen fusing with one side of the Golgi body and pinching off from the opposite side
• it chemically modifies substance made by the ER
• it stores and packages these substances in vesicles for secretion out of the cell

Question 13

How substances made by ER are moved out of the cell

Answer 13

1. Vesicles transports substances within the cell. Small vesicles containing substances made by ER are pinched off from ER
2. Vesicles then fuse with the Golgi body and release their contents in Golgi Body. The substances made by ER may be modified inside Golgi Body
3. Secretory vesicles containing these modified substances are pinched off from the golgi body. They then move to the cell membrane
4. Secretory vesicles fuse with the cell membrane and their contents are released out of cell

Question 14

Mitochondria

Answer 14

• small oval/ sausage-shaped organelles
• where aerobic respiration occurs, which releases energy

Question 15

Chloroplasts

Answer 15

• oval structures found in plant cells
• contains green pigment called chlorophyll
• chlorophyll is essential for photosynthesis

Question 16

Vacuoles

Answer 16

• fluid-filled space enclosed by a partially permeable membrane
• stores substances within cell
• plants cells have 1 large vacuole containing cell sap
• animal cells have many small temporary vacuoles that contain water and food substances

Question 17

Differnciation

Answer 17

• process by which a cell becomes specialised for specific function

Question 18

How a rbc is adapted to its function

Answer 18

• contain haemoglobin which bind reversibly with oxygen to form oxyhemoglobin and transports it all over the body
• has a circular biconcave shape which increases surface area-to-volume ratio, increasing rate of diffusion
• lacks a nucleus, enabling rbc to store more haemoglobin to transport more oxygen
• is flexible and therefore can squeeze through capillaries easily

Question 19

How muscle cell is adapted to its function

Answer 19

• is elongated and cylindrical in shape, containing many nuclei and mitochondria
• has mitochondria to provide energy for contraction of muscle cells

Question 20

How root hair cell is adapted to its function

Answer 20

• has a long and narrow root hair to increase surface area-to-volume ratio to absorb water and mineral salts at a higher rate

Question 21

When to use surface area to volume ratio

Answer 21

1. Red blood cells
2. Root hair cells
3. Emulsification
4. Dialysis Machine Tubing