Cells

Question 1

What does a cell consist of?

Answer 1

• each cell contains a living material called protoplasm

- consist of cell surface membrane, nucleus, cytoplasm

Question 2

Cell surface membrane/plasma membrane

Answer 2

• surrounds cytoplasm of cell
• made up of lipids and proteins
• partially permeable, control substance entering and leaving cell

Question 3

Cytoplasm

Answer 3

• part of protoplasm, between cell surface membrane and nucleus
• where most cell activities occur
• contains organelles which are specialized structures which carry out many functions in cell

Question 4

Nucleus

Answer 4

• consists of small round mass of denser protoplasm called nucleoplasm
• surrounded by nuclear envelope (membrane)
• controls cell activities e.g. cell growth, repair worn-out parts
• essential for cell division (rbc cannot divide)
• contain one or more nucleoli and chromatin

Question 5

Cellulose Cell wall

Answer 5

• made of cellulose
• protects cell from injury, gives cell fixed shape
• fully permeable

Question 6

Nucleus: Nuclear envelope

Answer 6

separates contents of nucleus from rest of cytoplasm

Question 7

Nucleus: Nucleoplasm

Answer 7

dense material within nucleus

Question 8

Nucleus: Nucleolus

Answer 8

-plays a part in making proteins in cell

Question 9

Nucleus: Chromatin

Answer 9

• mass of long thread-like structures found within nucleus
• each chromatin thread made up of proteins and DNA (hereditary info stored in here)
• DNA carries instructions of cell needs for carrying out activities
• during cell division, chromatin threads condense, become highly coiled structures called chromosomes

Question 10

Cytoplasm: Rough endoplasmic reticulum

Answer 10

• network of flattened spaces lined with a membrane
• surface appears rough when viewed under electron microscope
• ribosomes attached to its membrane
• outer surface of RER continuous with nuclear envelope
• transports proteins made by ribosomes to Golgi Apparatus for secretion out of cell

Question 11

Cytoplasm: Ribosomes

Answer 11

• small round structures
• attached to membrane of ER or lie freely in cytoplasm
• essential in protein synthesis in cell
• those attached to ER usually transported out of cell
• those lying freely in cytoplasm make proteins that are used within cytoplasm in cell

Question 12

Cytoplasm: Smooth Endoplasmic Reticulum

Answer 12

• no ribosomes attached to membrane/surface
• more tubular than RER, connected to RER
• synthesis of fats, steroids (sex hormones in mammals)
• detoxification, convert harmful substances to harmless materials

Question 13

Golgi apparatus

Answer 13

• disc-like shape
• stack of flattened spaces surrounded by membranes
• vesicles(transport substances within cell) fuse from one side of GA, pinch off from opp side
• GA chemically modifies substances made by ER
• stores and packages these substances in vesicles for secretion out of cell

Question 14

How substances made by organelles in cell are released out of cell

Answer 14

1. Small vesicles containing substances made by ER, pinched off from ER
2. vesicles fuse with GA, release contents in it, substance made by ER may by modified in GA
3. Secretory vesicles containing modified substances pinched off from GA, move to cell surface membrane
4. Secretory vesicles fuse with cell surface membrane, contents released out of cell

Question 15

Mitochondria

Answer 15

• oval/sausage shaped
• aerobic respiration occurs here
• food substances oxidised, release energy
• used fro cell activities e.g. growth, reproduction

Question 16

Chloroplasts

Answer 16

• oval shaped

- contains green pigment chlorophyll (essential for photosynthesis to make food for plant)

Question 17

Vacuoles

Answer 17

• fluid-filled space enclosed by membrane , store substances within cells
• animal: small, numerous, contain food and water, exist temporarily
• plant: large central vacuole, contain cell sap (dissolved substances e.g. sugars, mineral salts, amino acids), enclosed by partially permeable membrane called tonoplast

Question 18

Centrioles

Answer 18

• play a part in cell division

- only in animal cells