Cells

Question 1

Describe the fluid mosaic model of cell membrane

Answer 1

Cell membrane is fluid in that phospholipids and proteins are not stationary but can move rapidly across the surface of the membrane
Cell membrane is mosaic in that many different protein molecules are randomly scattered and embedded throughout phospholipid bilayer

Question 2

What is the function of cell membrane

Answer 2

It is partially permeable, functions to separate and protect cell from surrounding environment and control how substances move in and out of the cell

Question 3

What does cytoplasm contain

Answer 3

Cytosol, cytoskeleton and organelles

Question 4

Define cytosol

Answer 4

Aqueous solution of essential ions, soluble proteins and soluble organic compounds such as sugars and amino acids

Question 5

Define cytoskeleton

Answer 5

Network of protein fibres that give support, mobility and regulation to the cell

Question 6

Define cytoplasmic streaming

Answer 6

The movement of the fluid substance withiin a plant or animal cell and aids in transport of materials and organelles around the cell

Question 7

Describe the structure of the nucleus

Answer 7

Largest organelle within the eukaryotic cell, usually spherical. Consists of nuclear envelope which separates nucleus from the cytoplasm. Contains nucleolus which synthesises ribosomes. Contains DNA. Found in all eukaryotic cells except matured red blood cells

Question 8

What is the function of the nucleus

Answer 8

Contains hereditary material and controls activities of the cell. Cells normally contain one nucleus (uninucleated) but may be binucleated or multinucleated

Question 9

Describe structure of RER

Answer 9

A system of flattened membrane-bound sacs. Appears “rough” under electron microscope because of presence of ribosomes on its surface

Question 10

Describe function of RER

Answer 10

Protein synthesis, polypeptide chain synthesised by ribosomes will be folded in RER

Question 11

Describe structure of SER

Answer 11

Consists of fine tubules

Question 12

What are the functions of SER

Answer 12

Lipid synthesis, detoxification of drugs and poisons, storage and release of calcium ions

Question 13

Describe structure of Golgi apparatus

Answer 13

Consists of stacks of flattened membrane-bound sacs

Question 14

Describe function of Golgi apparatus

Answer 14

Chemically modifies products received from the ER and packages them, before sending them to destinations inside or out of the cell using vesicles

Question 15

Describe structure of lysosomes

Answer 15

Small spherical vesicles surrounded by single membrane. Contains hydrolytic enzymes such as lipases, proteases and nucleases.

Question 16

Describe function of lysosomes

Answer 16

To digest materials made in the cell or taken in from outside by phagocytosis
To digest worn-out organelles in the cell, process known as autophagy

Question 17

Describe structure of animal vacuoles

Answer 17

Fluid-filled sac bounded by single membrane. Formed either by pinching-off part of cell membrane or enlargement of vesicle from Golgi apparatus. Usually relatively smaller and exists temporarily

Question 18

Describe function of animal vacuoles

Answer 18

Can be food vacuoles formed by phagocytosis

Question 19

Describe structure of plant vacuoles

Answer 19

Mature plant cells have permanent large central vacuole and occupies over 80% of cell volume. Enclosed by single, partially permeable membrane called tonoplast. Filled with cell sap, solution of dissolved substances such as sugars, ions, waste products and pigments

Question 20

Describe function of plant vacuoles

Answer 20

Storage of nutrients such as protein storage in seeds and inorganic ions. Disposal sites for metabolic byproducts that would endanger cell if they accumulated in the cytosol. May contain pigments that colour cells(e.g. coloured petals to attract pollinators)

Question 21

Describe structure of mitochondria

Answer 21

Rod-shaped or spherical, bounded by double membrane

Question 22

Describe function of mitochondria

Answer 22

Involved in aerobic respiration. ATP is “energy molecule” living organisms. Mitochondria is abundant in metabolically active cells (e.g. muscle and liver cells)

Question 23

Describe structure of chloroplasts

Answer 23

Bounded by double membrane, contains chlorophyll, contains thylakoids and stroma

Question 24

Describe function of chloroplasts

Answer 24

Site of photosynthesis

Question 25

Describe structure of ribosomes

Answer 25

Small, round structure found in all cells May occur as free ribosomes suspended in the cytosol or bound to rough ER

Question 26

Describe function of ribosomes

Answer 26

Sites of polypeptide synthesis. Free ribosomes make proteins that function within the cytosol. Bound ribosomes generally make proteins destined for insertion into membranes, for packaging within certain organelles such as lysosomes, or for export from the cell

Question 27

Describe structure and function of centrioles

Answer 27

Small, hollow cylinders that occur in pairs, found in animal cells but absent in plant cells They play a role in cell division in animal cells

Question 28

Describe protein synthesis and secretion in a cell

Answer 28

Polypeptide chains are synthesised at the ribosomes and folded at RER. Transport vesicles containing substances made by ER pinched off from ER. Transport vesicles fuse and release substances into the Golgi apparatus. Secretory vesicles containing modified substances are pinched off from Golgi apparatus. Secretory vesicles move towards and fuse with cell membrane, releasing substances outside the cell by exocytosis

Question 29

Describe formation of lysosome

Answer 29

Enzyme contents are synthesised on rough ER and transported via transport vesicle to the Golgi apparatus for further processing. Vesicle containing processed enzymes buds off from Golgi apparatus, forming a lysosome. Enzymes have to be kept apart from rest of cell or they will destroy the cell

Question 30

What are similarities between animal and plant cells

Answer 30

Both cells contain cell membrane, mitochondria, nucleus and cytoplasm (and others)

Question 31

Compare differences between animal and plant cell

Answer 31

Chloroplasts present in large numbers in photosynthetic cells(plant cell), absent(animal) Centrioles present(animal), absent(plant) Plant vacuole is present as single, large and central, animal vacuoles are small and numerous Plant cell surrounded by cell wall in addition to cell membrane, cell wall absent and animal cell only surrounded by cell membrane

Question 32

Define cell specialisation

Answer 32

Multicellular organisms are composed of different types of cells and structure of cells is differently adapted to perform specific function. Cells differ in size and shape and they perform specific functions.

Question 33

Describe adaptation of root hair cell and how it helps function

Answer 33

Adaptation: Presence of long narrow extension Function: Absorption of water and mineral salts Use: Increased surface area to volume ratio due to presence of long narrow extension, increases rate of diffusion of mineral salts and osmosis

Question 34

What are three adaptations of red blood cell and how do they help RBC in function

Answer 34

Presence of haemoglobin: Haemoglobin can combine with oxygen Absence of nucleus: Allows more haemoglobin to be packed in the cell Biconcave shape: Increases surface area to volume ratio to increase rate of diffusion of oxygen and carbon dioxide

Question 35

What are adaptations of muscle cell and how does it help function

Answer 35

Elongated and cylindrical in shape, contains nuclei and mitochondria. Has mitochondria to provide energy for contraction of muscle cell

Question 36

What is level of complexity of biological molecules in increasing order (e.g. macromolecule)

Answer 36

Macromolecule, organelle, cell, tissue, organ, organ system

Question 37

Define organelle

Answer 37

Differentiated structure within cell which performs specific function

Question 38

Define cell

Answer 38

The building blocks of life, simplest units that have all characteristics of life

Question 39

Define organ

Answer 39

Structure made up of different tissues working together to perform specific function

Question 40

Define tissue

Answer 40

A group of similar cells which work together to perform specific function