Cells, tissues, organs

Question 1

Why can’t cells grow too large?

Answer 1

As a cell grows, its volume increases faster than surface area.

This makes exchange of substances inefficient.

Large cells may also struggle to be controlled by a single nucleus.

Question 2

What are multinucleated cells?

Answer 2

Cells with more than one nucleus.

This helps control larger volumes of cytoplasm.

Example: Muscle cells.

Question 3

Why is cell specialization important in multicellular organisms?

Answer 3

Allows cells to perform specific functions (e.g., feeding, defense).

Increases efficiency.

Example: Red blood cells carry oxygen but can’t divide (no nucleus).

Question 4

What is a tissue?

Answer 4

A group of similar cells working together to perform a specific function.

Examples: Muscle tissue, connective tissue.

Question 5

What is an organ?

Answer 5

A structure made of two or more tissues working together.

Performs a specialized function (e.g., heart, leaf).

Question 6

Types of Human (Animal) Tissues

Answer 6

Connective – bones, cartilage, tendons

Epithelial – skin, lining of organs

Muscle – skeletal, smooth, cardiac

Nerve – brain, spinal cord, nerves

Reproductive – ovaries, testes

Question 7

Main Plant Tissue Types

Answer 7

Meristematic tissue – dividing cells (growth)

Permanent tissue – mature, non-dividing cells

Simple: parenchyma, collenchyma, sclerenchyma

Complex: xylem, phloem

Question 8

Meristematic Tissue

Answer 8

Made of actively dividing cells.

Totipotent – can become any cell type.

Types:
Apical – tips of roots and shoots
Lateral – thickness (cambium)
Intercalary – base of leaves/internodes

Question 9

Types of Simple Permanent Tissue

Answer 9

Parenchyma – soft parts; storage, photosynthesis

Collenchyma – support in young parts; thick corners

Sclerenchyma – dead, thick walls; support (e.g., nut shells)

Question 10

What is the Epidermis? What it includes?

Answer 10

Outer protective layer of plant cells

May have cuticle (waxy coating) to prevent water loss

Includes:
Stomata – gas exchange
Guard cells – control stomata
Trichomes – hair-like, reduce water loss and defend plant

Question 11

Complex Permanent Tissue: Xylem and Phloem

Answer 11

Xylem:
Conducts water and minerals upward

Made of: tracheids, vessels, xylem parenchyma, fibres

Phloem:
Transports food both directions

Made of: sieve tubes, companion cells, phloem fibres, parenchyma