1 — cells

Question 1

Characteristics of cell membrane

Answer 1

• Partially permeable
• Controls movement of substances entering/leaving the cell
• Made up of lipids&proteins

Question 2

Characteristics of Cytoplasm

Answer 2

• Site for chemical activities in cell to occur
• Contains specialised structures that perform a specific job within the cell: organelles
  
  • Endoplasmic reticulum
  • Golgi body
  • Ribosomes
  • Mitochondria

Question 3

Characteristics of nucleus

Answer 3

• May contain >/1 nucleoli & chromatin, which contains genetic information, DNA
• Controls cell activities, essential for cell division

Question 4

Characteristics of cell wall

Answer 4

• Made of cellulose
• Protects cell from injury
• Gives the cell a fixed shape
• Fully permeable

Question 5

Characteristics of chromatin

Answer 5

• Made up of proteins and DNA (deoxyribonucleic acid)
  
  • stores hereditary info
  • Carries instructions that a cell needs for carrying out its activities
  • condense and shortens to become chromosomes
    
    • Only present during mitosis (cell division)

Question 6

Endoplasmic reticulum (smooth vs rough comparison)

Answer 6

Appearance:
RER: Appears rough cus of ribosomes attached to membrane
SER: Appears smooth cus absence of ribosomes attached to membrane

Shape:
RER: A network of flattened spaces lined with a membrane (filled with fluid)
SER: More tubular than RER

Connections:
RER: Continuous with nucleus membrane
SER: Continuous with RER

Functions:
RER: Transport proteins made by ribosomes to Golgi Apparatus for excretion out of cell
SER: - Synthesise fats & steroids (sex hormones in mammals)
- Carries out detoxification: Converts harmful substances -> harmless substances

Question 7

Ribosomes

Answer 7

Sites to synthesise proteins
- Attached to RER membrane
- Proteins made transported out of cell (usually)
- Lie freely in cytoplasm
- Proteins made used within cell

Question 8

Golgi Body/Apparatus (GB/A)

Answer 8

• Consists of stack of flattened spaces surrounded by membranes
• Chemically modifies, stores & packages substances made by ER in vesicles for secretion out of cell

Question 9

Vesicles

Answer 9

• Transport substances within cell
• Contains substances made by ER, pinched off from ER -> fuse with GB, release contents into GB to be modified-> secretory vesicles (becomes secretory now) containing modified substances pinched off from GB -> move to cell membrane -> fuse with cell membrane -> contents released out of cell

Question 10

Mitochondria

Answer 10

• Singular: mitochondrion
• Site for aerobic respiration where glucose is oxidised to release energy [1] for cellular activities [1] (such as) Growth and Reproduction
• Glucose + oxygen -> CO2 + H2O + large amt of energy

Question 11

Chloroplasts

Answer 11

Contains a green pigment chlorophyll required for photosynthesis to occur

Question 12

Vacuoles

Answer 12

• A fluid-filled space enclosed by a partially permeable membrane
• Store substances within a cell
• Plant: large & central; contains cell sap
  
  • Contains dissolved substances like sugars
  • Mineral salts
  • & amino acids
• Animal: many & small; contain water & food substances; usually exists temporarily

Question 13

Differences betw plant cell n animal cells

Answer 13

Presence of cell wall:
PC: P (present)
AC: A (absent)

Vacuoles:
PC: Large, central, contains cell sap
AC: Many, small, contains water & food substances

Presence of chloroplasts
PC: P
AC: A

Presence of centrioles:
PC: A
AC: P

Question 14

Similarities betw a typical plant cell n an animal cell

Answer 14

Both has presence of protoplasm and presence of RER+SER

Question 15

Movement of proteins in cells

Answer 15

• Proteins made / synthesised by the ribosomes on the rough endoplasmic reticulum (RER) enter into RER. [1]
• The manufactured proteins are transported in vesicles that are pinched off from the RER and are transported to the Golgi apparatus. [1]
• The Golgi apparatus stores and chemically modifies the proteins made by RER and packages them into vesicles. [1]
• The secretory vesicles containing the modified proteins are pinched off from the Golgi apparatus. The vesicles then move to the cell membrane and fuse with the membrane. This releases the contents in the vesicles into the outside of the cell. [1]

Question 16

Differentiation Definition

Answer 16

Process by which a cell becomes specialised for a specific function

Question 17

RBCs characteristics

Answer 17

• Contains haemoglobin (red pigment) that binds to oxygen & transports it around body
• Has circular, biconcave shape -> ^ surface area-to-volume ratio -> oxygen can diffuse in & out faster
• Lacks nucleus -> more space -> Store more haemoglobin for transport of O2
• Flexible -> squeeze thru capillaries easily

Question 18

Muscle cell characteristics

Answer 18

• Elongated, cylindrical in shape
• Contains many nuclei + mitochondria to release energy for contraction of muscle cell
• ^ mitochondria -> ^ aerobic respiration -> faster release of energy for contraction of muscle cells

Question 19

Root hair cell

Answer 19

Long & narrow root hair -> ^ surface-area-to-volume ratio -> absorbs water + dissolved mineral salts faster

Question 20

Compare the structures of a RBC&RHC in carrying out their functions efficiently

Answer 20

• Similarity: increases SA:V for faster rate of diffusion of substances
• Differences: RBC no nucleus, RHC got nucleus; RBC got haemoglobin, RHC no; RHC got many mitochondria, RBC not a lot of mitochondria

Question 21

Compare and contrast the similarities and differences between plant cells and animal cells. [6]

Answer 21

Similarities:
Both have nucleus [1]
Both have cell membrane / mitochondria/ RER/ SER [1]

Differences:
Plant cell have cell wall but animal do not have [1]
Plant cell have chloroplast but animal do not have [1]
Plant cell have a large central vacuole but animal cells have small and numerous vacuoles [1]

Question 22

Identify a named organelle that can only be seen under electron
microscope and state its functions. [2]

Answer 22

Golgi apparatus [1]:
stores, chemically modifies and packages manufactured proteins in
vesicles for secretion out [1] of the cell
OR
Mitochondria [1]:
site of aerobic respiration where glucose is oxidised to release energy [1]
for cellular activities
OR
Rough Endoplasmic Reticulum [1]:
To transport proteins synthesised by ribosomes to the Golgi apparatus
for secretion out of the cell [1]
OR
Smooth Endoplasmic Reticulum [1]:
synthesises fats and steroids / convert harmful substances into
harmless substances via detoxification [1]

Question 23

Use a named example, describe the relationship between cells, tissue
and organ. [4]

Answer 23

The heart consists of different tissues to perform a specific function [1]
such as the muscle tissue, connective tissue, blood tissues and nerve tissues. [1] *any 3 example

These tissues are a group of similar cells that work together to perform a specific function. [1] Eg. muscle tissue contains similar muscle cells with which synchronize their contractions to bring about the contraction of the
tissue. [1]

OR
The leaf consists of different tissues to perform a specific function [1]
such as the palisade tissue, spongy mesophyll tissue, xylem tissues and
phloem tissues. [1] *any 3 examples
These tissues are a group of similar cells that work together to perform a specific function. [1] Eg. palisade tissue contains similar palisade
mesophyll cells with chloroplasts to trap sunlight to make glucose by
photosynthesis [1]

Question 24

Describe how the protein is synthesised and transported in the cell for secretion. [4]

Answer 24

Proteins made / synthesised by the ribosomes on the rough endoplasmic reticulum (RER) enter into RER. [1]
The manufactured proteins are transported in vesicles that are pinched off from the RER and are transported to the Golgi apparatus. [1]

The Golgi apparatus stores and chemically modifies the proteins made by
RER and packages them into vesicles. [1]

The secretory vesicles containing the modified proteins are pinched off from the Golgi apparatus. The vesicles then move to the cell membrane and fuse with the membrane. This releases the contents in the vesicles into the
outside of the cell. [1]

Question 25

How does the cell wall help to maintain turgor of a plant cell?

Answer 25

It supports the cell membrane.

Question 26

What structures are involved in enzyme synthesis in a cell?

Answer 26

Ribosomes on RER Nucleus (contains genetic info that codes for enzyme) Mitochondria (provides energy to manufacture enzyme) Golgi apparatus (modifies, sorts and packages)

Question 27

Suggest why liver cells have many mitochondria. [2]

Answer 27

The mitochondrion is the site of aerobic respiration where chemical energy in the form of ATP is released. There are large numbers of mitochondria in liver cells to release the energy needed to carry out metabolic reactions, for example protein synthesis.

Question 28

Outline how the organelles and membrane systems in muscle cells use the mRNA to produce and secrete the ‘spike’ protein into the blood stream. [3]

Answer 28

Ribosomes use genetic code / information in mRNA to synthesise spike protein; Spike protein enters the rough endoplasmic reticulum and is transported to the Golgi body; Golgi body sorts, modifies and packages spike proteins into secretory vesicles; Secretory vesicles releases the spike protein out of the cell into the blood capillaries;

Question 29

Greatest and lowest density of mitochondria in plants [4]

Answer 29

Greater density of mitochondria Root hair cell / Companion cell [1] Cell needs more energy to be released from aerobic respiration for active transport of dissolved mineral salts/ dissolved sucrose and amino acids into the cell. [1] Lower density of mitochondria Sieve tube cell [1] The metabolic processes needed to keep the sieve tube cell alive take place in the companion cells, including aerobic respiration hence there are no mitochondria in the sieve tube cells. [1] OR Epidermal cell [1] The main function of epidermal cells is to protect the plant from mechanical damage, hence, these cells only require minimal metabolic processes and a lower density of mitochondria to stay alive and carry out their function. [1]