Biology Cells chapter 1

Question 1

Characteristics of cells

Answer 1

• Basic building blocks of life
• They have all characteristics of life, needs food, water and air to survive
• Will eventually die, will grow, able to reproduce and respond to changes
• Many chemical reactions occur in the cell

Question 2

Light micrograph

Answer 2

Magnifies 1000x on a cellular level

Question 3

Electron micrograph

Answer 3

magnifies more than 200 000x able to see things on a molecular level

Question 4

What does a cell consist of?

Answer 4

Protoplasm- which is everything in the cell membrane, including cell membrane, excluding cell wall. Made of cell surface membrane, cytoplasm and nucleus

Question 5

Description of cell surface membrane

Answer 5

• Serves as a boundary (without it, everything in the cell would leak out and the cell would die)
• It is partially permeable
• Controls the substances entering or leaving the cell

Question 6

Description of cytoplasm

Answer 6

• Most cell activities occur there
• It contains specialised structures called organelles like nucleus, vacuole

Question 7

Description of nucleus and what it is made up of

Answer 7

-Contains genetic material
- controls all activities within the cell
- May contain one or more nucleoli and chromatin, which is a condensed form of DNA(genetic material)
Nucleoplasm- A small round denser protoplasm of the nucleus (all the fluid inside the nucleus)
Nuclear envelope- surrounds the nucleoplasm
Nucleolus- a protein that helps to replicate DNA

Question 8

Description of Chromatin

Answer 8

• Compacted form of DNA
• It is a network of threadlike structures that controls cell activities e.g. cell division
• It’s made up of deoxyribonucleic acid (DNA) which carries hereditary information
• Chromatin threads condense into chromosomes when the cell is dividing

Question 9

Cell wall

Answer 9

• Found in plant cells but absent in animals cells
• made of cellulose
• It protects the cell from injuries and gives the cell its shape
• It is fully permeable

Question 10

How to do a longitudinal cut

Answer 10

Longitudinal section- cutting along the long axis of the cell

Question 11

How to do a transverse cut

Answer 11

Transverse section- Cutting at right angles to the longitudinal plane

Question 12

How to examine the cell clearly

Answer 12

By staining the cell with either iodine or methylene blue, as cells are usually transparent and colourless

Question 13

What are the two types of endoplasmic reticulum(ER)?

Answer 13

Rough endoplasmic reticulum (RER)
Smooth endoplasmic reticulum (SER)

Question 14

Rough endoplasmic reticulum description

Answer 14

• Appears rough because ribosomes are attached to its surface
• The ribosomes are required to make proteins
• The RER transports proteins to the Golgi apparatus for secretion out of the cell
• Ribosome can be found freely in the cytoplasm, they synthesise proteins which are used within the cell

Question 15

Smooth endoplasmic reticulum description

Answer 15

• SER is more tubular and does not have ribosomes
• It synthesis’s substances such as fats and steroids (sex hormones)
• It is involved in detoxification
  Organs rich in SER are the testes and the ovaries as sex hormones are steroids that are synthesised

Question 16

Golgi apparatus description

Answer 16

• consists of flattened spaces surrounded by membranes
• It modifies substances made by the endoplasmic reticulum
• The Golgi apparatus chemically modifies, stores and packages the substances in vesicles for secretion out of the cell

Question 17

How the Golgi apparatus works

Answer 17

1. Vesicles containing substances made in the ER pinch off from the ER
2. Vesicles then fuse with the Golgi apparatus
3. The substances in the vesicles are released into the Golgi apparatus and are chemically modified
4. Secretory vesicles containing the modified substances pinch off from the Golgi apparatus and move towards the cell surface membrane
5. The secretory vesicles fuse with the cell surface membrane and release contents into exterior of cell

Question 18

Mitochondria

Answer 18

Site for aerobic respiration where glucose is oxidised to release energy for cellular activities (enzymes are involved)
Glucose+ Oxygen+ Carbon dioxide+ water + large amount of energy

Question 19

Chloroplasts

Answer 19

Oval structures containing pigment chlorophyll which is required for photosynthesis to occur

Question 20

Vacuoles

Answer 20

• Store substances within the cell
• Animal cells have many vacuoles containing water and food substances
• Plant cells have a large central vacuole containing cell sap ( The large central vacuole can store a lot of water, so the cell can swell up, maintaining its shape by the cell wall so the cell will not burst. This makes the cell firm, allowing the plant to stay upright)

Question 21

Differentiation

Answer 21

The process by which a cell becomes specialised for a specific function
Examples of specialised cells are red blood cells and root hair cells

Question 22

Muscle cells

Answer 22

• Elongated and cylindrical in shape
• has multiple cells fuse together to form a long fibre
• Rich in mitochondria and nuclei to release a lot of energy to compensate for the muscle’s constant contraction and expansion

Question 23

Red blood cell

Answer 23

Haemoglobin in the cytoplasm of red blood cells transports oxygen from lungs to all parts of the body
A red blood cell has no nucleus, thus enabling it to have more space in the cytoplasm to contain more haemoglobin and hence transports more oxygen when oxygen binds to form oxyhaemoglobin

It has a circular, biconcave shape, increasing the surface area to volume ratio. This increase the rate of diffusion of oxygen molecules into and out of the cell. It has a cave-in structure to have thinner central portion, to have a larger surface area but same volume, this is it to increase rate of absorption of oxygen