Cell Structure & Organization

Question 1

Plant cell exclusive characteristics:

Answer 1

• vacuole (stores food+water, helps maintain shape of cell)
• cell wall (rigid wall to maintain shape of cell)
• chloroplasts (contains chlorophyll to absorb light energy

Question 2

Specialised cells:

Answer 2

• red blood cell
• muscle cell
• ciliated cell
• root hair cell
• xylem vessel
• palisade cell

Question 3

Red blood cell:

Answer 3

Function:
- O2/CO2 transport

Adaptation:

• bi-concave shape (large surface area)
• anucleate (no nucleus; to accommodate more O2/CO2)
• flexible (to fit through blood vessel lumen)
• contains haemoglobin (to bind O2/CO2)

Question 4

Muscle cell:

Answer 4

Function:
- contracts to get structures closer together

Adaptation:

• long
• contains lots of mitochondria (more energy!!)
• lots of protein fibers for contraction

Question 5

Ciliated cell:

Answer 5

Function:
- move mucus up the trachea

Adaptation:
- has cilia (to sweep mucus upwards)

Question 6

Root hair cell:

Answer 6

Function:
- absorb minerals and water

Adaptation:

• elongated shape (large surface area)
• lots of mitochondria (supplies energy for active transport)
• concentrated vacuole (helps absorb water via osmosis)

Question 7

Xylem vessel:

Answer 7

Function:

• transport water
• support plant

Adaptation:

• no cytoplasm (so water passes freely)
• no cross walls (cells connect to form hollow tube)
• lignin (strong + waterproof)

Question 8

Function of cell membrane:

Answer 8

To control movement of substances in and out of the cell

Question 9

Function of cell wall:

Answer 9

To withstand the inner pressure of the cell

Question 10

Define organelle

Answer 10

A specialised part of a cell (e.g. nucleus, chloroplast, mitochondria)

Question 11

Define cell

Answer 11

Smallest part of a living biological organism that can operate independently as a unit (e.g. RBC)

Question 12

Define tissue

Answer 12

A group of cells with similar structures and common functions (e.g. muscles)

Question 13

Define organ

Answer 13

A structure made up of a group of tissues to perform specific functions (e.g. heart)

Question 14

Define organ system

Answer 14

A group of organs with related functions, working together to perform various body functions (e.g. respiratory system)

Question 15

Define organism

Answer 15

An individual made up of organ systems that work to keep that individual alive

Question 16

Phloem vessel:

Answer 16

Function:
- transport of materials in translocation processes

Structure:

• long, continuous strands called vascular bundles
• unlike xylem, it is living
• is made up of: sieve elements; companion cells; and supportive cells

Question 17

What are sieve elements?

Answer 17

• group of cells in phloem
• responsible for moving sugary fluids
• no nucleus and few organelles when mature (prior to maturing, sieve tube cells do contain vacuoles and other organelles, though)
• rely on companion cells for energy
• have sieve areas: clusters of pores reinforced by platelets of callose (a polysaccharide)

Question 18

What are sieve cells?

Answer 18

Out of the 2 main conducting cells in the phloem, the sieve cell is more primitive, and is generally found in seedless vascular plants.

Question 19

Define vascular plant:

Answer 19

A plant with a specialised transportation system (the phloem).

Question 20

What are sieve-tube cells?

Answer 20

• more advanced type of conducting cell
• elongated individual cells arranged end-to-end
• conducts food materials throughout the plant
• sieve areas in these cells are called sieve plates

Question 21

What are companion cells?

Answer 21

• specialised parenchyma cells
• carries out basic cellular functions of sieve elements
• has more ribosomes and mitochondria than normal cells, so is more metabolically active than normal cells
• the cytoplasm of a companion cell is connected to sieve-tube elements via plasmodesmata

Question 22

Define plasmodesmata

Answer 22

A narrow thread of cytoplasm passing through the cell walls of adjacent plant cells

Question 23

What are parenchyma?

Answer 23

The most abundant cell type in plants, and are usually unspecialised. Characteristics:

• thin cell wall
• large vacuole for storage
• spherical
• regular shape
• elastic
• lots of intracellular space

Functions include photosynthesis, storage, and secretion.

Question 24

What are collenchyma?

Answer 24

They can be found just below the epidermis in petiole, leaves, and stems, and are usually specialised. Characteristics:

• irregularly thickened walls (with cellulose)
• prism shape
• plastic deformation (is elastic, but remains deformed when structure is altered)

Functions include support and transport of nutrients.

Question 25

What are sclerenchyma?

Answer 25

Can be found in mature parts of a plant, especially in woody or herbaceous plants. They are generally specialised.
Characteristics:
- die upon maturing
- very thick, lignified cell wall
- impermeable
- in transport-specialised sclerenchyma, the cell wall will contain holes called pits

Functions include support, protection, and transport of water/nutrients.

Question 26

Common organelles:

Answer 26

• cell membrane
• mitochondria
• nucleus
• cytoplasm

Question 27

Function of cell membrane

Answer 27

• forms a barrier
• controls movement of substances in and out of the cell
• keeps contents of cell inside

Question 28

Function of nucleus

Answer 28

• controls activities in the cell
• contains genetic information
• controls how cells develop/divide/reproduce/grow