biology chpt 1.

Question 1

What is the basic features of a cell?

Answer 1

1. Cell Surface Membrane
2. Cytoplasm
3. Genetic Material (Nucleus)

Question 2

What is an organelles ?

Answer 2

Specialised units found in a cell.

Question 3

What are the two microscopes that can be used to study parts of the cell?

Answer 3

Light and Electron Microscope

Question 4

What are the structures that are visible under both light and electron microscopes?

Answer 4

1. Nucleus
2. Cell surface membrane
3. Cell Wall
4. Cytoplasm
5. Vacuole
6. Chloroplast

Question 5

What are the structures visible only under the electron microscope ?

Answer 5

1. Mitochondria
2. Ribosomes

Question 6

What is the structure and function of a Cell Surface Membrane ?

Answer 6

Structure:
~The membrane is partially permeable.
~The membranes ae fluid in nature ( not rigid )
~ It is made up of proteins, lipids and carbohydrates

Functions:
~Separates the cell from its external environment
~Controls the movement of substances into and out of the cell

Question 7

What is the structure and function of a Cytoplasm?

Answer 7

Structure:
- A solution that is composed of mainly water and dissolved substances
- It exists in sol (liquid) or gel (semi-solid) states.
- Cytoplasmic streaming/movement of liquid can sometimes be observed

Function:
- Medium where most cellular functions and chemical reactions take place.
- Substances are transported through the cytoplasm

Question 8

What is the structure and function of a nucleus?

Answer 8

Structure:
- Contains DNA (Genetic material)
May appear as;
+ Chromatin (Non-dividing cell) - unwound DNA, highly elongated threads.
+ Chromosome - condensed DNA (dividing cell)

Function:
- Contains genetic material (DNA) that controls cell activities like growth and repair
- Plays a role in cell division

Question 9

What is the structure and function of a Ribosome?

Answer 9

Structure:
- Made up of RNA (ribronucleic acids) and proteins
- Free ribosomes are found in the cytoplasm
- Some ribosomes are attached to the rough endoplasmic reticulum

Function:
- Proteins synthesis
+ Free ribosomes synthesise proteins for use inside the cell
+ Ribosomes attached to RER synthesise proteins to be exported out of the cell.

Question 10

What is the structure and function of a Mitochondrion(1)? [Plural: Mitochondria]

Answer 10

Structure:
- Ovoid (not avoid) in shape
- Posesses a double membrane. The inner membrane is highly folded

Function:
- Site of cellular respiration which releases energy for cellular activities

Question 11

What is the structure and function of a Vacuole?

Answer 11

Structure:
- Fluid-filled space enclosed by a membrane
- In plant cells, vacuoles are usually large and central, enclosed by a membrane called tonoplast.
- Animal vacuole are smaller

Functions:
Plant vacuole:
cell sap inside the vacuole contains dissolved sugars, mineral salts, amino acids and waste products

Animal vacuoles:
Hold water and food substances ( temporarily )

Question 12

What are the structures found only in the plant cell?

Answer 12

1. Cell Wall
2. Chloroplast

Question 13

What is the structure and function of Cell Wall?

Answer 13

Structure:
- Outermost part of the plant cell next to the cell surface membrane
- Freely permeable to molecules entering/leaving the cell
- The cell wall is a rigid layer made of cellulose ( a type of carbohydrate )

Functions:
- Provides protection, shape and mechanical support to the cell
- Prevents the cell from bursting when cell is placed in a medium of high water potential

Question 14

What is the structure and function of a Chloroplast?

Answer 14

Structure:
- Oval structure which consists of double membrane
- Contains a green pigment called chlorophyll (molecule)

Functions:
- Chloroplast are sites of photosynthesis
- Not all plant cells contains chloroplast, as not all plant cells are adapted for photosynthesis ( e.g. root hair cells )

Question 15

What are the specialised cells ?

Answer 15

1. Red Blood Cell
2. Root Hair Cell
3. Muscle Cell

Question 16

What is the structure and function of Red Blood Cell ?

Answer 16

Structure:
- Biconcave in shape
- Absence of nucleus
- Flexible cell surface membrane
- Contains haemoglobin

Function:
- Increase surface area to volume ratio to increase rate of diffusion of oxygen molecules into and out of the cell so as to increase rate of transportation of oxygen molecules
- Increase the amount of haemoglobin that can be packed to increase the carrying capacity of oxygen molecules
- Allow the cell to alter its shape when travelling along narrow blood vessels ( capillaries )
- Binds reversible to oxygen and transprts it to the body

Question 17

What is the structure and function of Root Hair Cell?

Answer 17

Structure:
- Long, narrow protrusion
- Water potential lower in cell sap compared to surrounding soil solution
- Numerous mitochondria
- Uniformly thin cell wall

Function:
- Increases surface area to volume ratio to increase the rate of absorption of water molecules and mineral ions
- Maintains a steep water potential gradient to allow water moleculest continuosly enter the cell by osmosis
-Release more energy via respiration to increase rate of absorption of mineral ions
- Reduces distance for diffusion to increase rate of absorption of wter molecules and mineral ions

Question 18

What is the structure and function of Muscle Cell?

Answer 18

Structure:
-Numerous mitochondria
- Has contractile protein fibres
- Elongated and cylindrical in shape
- Numerous nuclei

Function:
- Reduces distances for diffusion to increase rate of absorption of water molecules and mineral ions
- Release more energy via respiration for contraction of the muscle cell
- Contract and relax to bring about good movement
-Allows for easy arrangement into pralel arrays which increasese the strength of the muscles
- To allow for more synthesis and secretion of skeletal muscle proteins to support increased rate of muscle contraction + cell dvision for cell replacement

Question 19

What is the structure and function of Muscle Cell?

Answer 19

Structure:
-Numerous mitochondria
- Has contractile protein fibres
- Elongated and cylindrical in shape
- Numerous nuclei

Function:
- Reduces distances for diffusion to increase rate of absorption of water molecules and mineral ions
- Release more energy via respiration for contraction of the muscle cell
- Contract and relax to bring about good movement
-Allows for easy arrangement into pralel arrays which increasese the strength of the muscles
- To allow for more synthesis and secretion of skeletal muscle proteins to support increased rate of muscle contraction + cell dvision for cell replacement