[bio] cells

Question 1

what is a cell?

Answer 1

a basic unit of structure and function. it is the simplest unit with all characteristics of life

Question 2

what are phospholipids?

Answer 2

a major component of biological membranes

Question 3

special thing about phospholipids in cell membranes?

Answer 3

made up of two layers of phospholipids - phospholipid bilayer

Question 4

why is phospholipid bilayer?

Answer 4

phospholipid tail is hydrophobic, needs the hydrophilic head to be facing outwards in contact with the extra cellular fluid outside the phospholipid bilayer

Question 5

why is the cell membrane fluid

Answer 5

phospholipids and proteins are not stationary but can move rapidly across the surface of the membrane

Question 6

why is the cell membrane mosaic

Answer 6

many different protein molecules are randomly scattered and embedded throughout the phospholipid bilayer

Question 7

why are cell membranes partially permeable?

Answer 7

due to the nature of the phospholipids, only small hydrophobic molecules can pass through the phospholipid bilayer. as such, for hydrophilic or water-soluble molecules are unable to pass through the cell membrane, transport proteins are required.

Question 8

what do you mean by partially permeable?

Answer 8

cell membrane only allows certain substances to pass through it

Question 9

functions of partially permeable cell membrane

Answer 9

it functions to separate and protects a cell from its surrounding environment and controls how substances move in and out of the cell

Question 10

what does cytoplasm contain

Answer 10

• cytosol
• cytoskeleton
• organelles

Question 11

what is cytosol?

Answer 11

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

Question 12

what is cytoskeleton?

Answer 12

network of protein fibres that give support, motility and regulation to the cell

Question 13

what is organelles?

Answer 13

structures with specialised functions, suspended in the cytosol

Question 14

what is cytoplasmic streaming

Answer 14

the movement of the fluid substance within a plant or animal cell

Question 15

how does cytoplasmic streaming help?

Answer 15

aids in the transport of materials and organelles around the cell

Question 16

structure of nucleus

Answer 16

largest organelle within the eukaryotic cell, usually spherical

Question 17

what does the nucleus contains

Answer 17

• nuclear envelope
• nucleolus
• dna

Question 18

what does nuclear envelope do

Answer 18

separates nucleus from the cytoplasm

Question 19

what does nucleolus do

Answer 19

synthesise ribosomes

Question 20

where are nucleus found

Answer 20

in almost all eukaryotic cells, except matured red blood cells

Question 21

function of nucleus

Answer 21

• contains the hereditary material (dna)
• controls activities of the cell

Question 22

structure of rough endoplasmic reticulum

Answer 22

a system of flattened membrane-bound sacs

Question 23

how does it look under the microscope

Answer 23

appears “rough” under electron microscope because of the presence of ribosomes on its surface

Question 24

functions of rer

Answer 24

protein synthesis - polypeptide chain synthesised by the ribosomes will be folded in the rer

Question 25

structure of ser

Answer 25

consists of fine tubules

Question 26

function of ser

Answer 26

- lipid synthesis - detoxification of drugs and poisons - storage and release of calcium ions

Question 27

structure of Golgi apparatus

Answer 27

consist of stacks of flattened membrane-bound sacs

Question 28

function of Golgi apparatus

Answer 28

chemically modifies products receive from the er and packages them, before sending them to destinations inside or out of the cell using vesicles

Question 29

structure of lysosomes

Answer 29

small, spherical vesicles surrounded by a single membrane

Question 30

what does lysosomes contain

Answer 30

hydrolysis enzymes such as lipases, proteases and nucleases

Question 31

functions of lysosomes

Answer 31

- to digest materials made in the cell or take in from outside by phagocytosis (e.g. food vacuoles in Amoeba) - to digest worn-out organelles in the cell, a process known as autophagy

Question 32

structure of animal vacuoles

Answer 32

fluid-filled sac bound by a single membrane

Question 33

how are animal vacuoles formed?

Answer 33

either by the pinching-off part of the cell membrane or by enlargement of a vesicle from the Golgi apparatus

Question 34

shape and size of animal vacuole?

Answer 34

usually relatively smaller and exists temporarily

Question 35

function of animal vacuoles?

Answer 35

food vacuoles: formed by phagocytosis. in the case of intracellular digestion by macrophages

Question 36

structure of plant vacuoles

Answer 36

enclosed by single, partially permeable membrane called the tonoplast

Question 37

where is plant vacuoles found?

Answer 37

in mature plant cells, the large central vacuole is permanent and occupy over 80% of the cell volume

Question 38

what is in the plant vacuole?

Answer 38

filled with cell sap, a solution of dissolved such as sugars, ions, waste products, and pigments

Question 39

function of plant vacuole

Answer 39

- storage of nutrients such as protein storage in seeds and inorganic ions, e.g. K+ and Cl- - disposal sites for metabolic by-products that would endanger the cell if they accumulated in the cytosol - may contain pigment that colour the cell, e.g. red and blue pigments of petals to attract pollinators

Question 40

structure of mitochondria

Answer 40

rod-shaped or cylindrical, bounded by double membrane

Question 41

where is mitochondria found?

Answer 41

in plant and animal cells

Question 42

function of mtiochondria

Answer 42

- involved in aerobic respiration - contains DNA - ATP is the "energy molecule" in living organisms

Question 43

where is mitochondria found abundant in?

Answer 43

metabolically active cells - e.g. muscle and liver cells

Question 44

structure of chloroplast

Answer 44

bounded by a double membrane

Question 45

what does chloroplast contain?

Answer 45

- chlorophyll - thylakoids and stroma

Question 46

function of chloroplast

Answer 46

site of photosynthesis

Question 47

structure of ribosomes

Answer 47

small, round structures found in all cells

Question 48

special thing about ribosomes?

Answer 48

may occur as free ribosomes suspended in the cytosol or bound to rough er

Question 49

functions of ribosome?

Answer 49

- site of polypeptide synthesis - free ribosomes generally make proteins that will function within the cytosol - bound ribosomes generally make protein that are destined for insertion into membranes, for packaging within certain organelles such as lysosomes, or for export from the cell

Question 50

strucute of centrioles

Answer 50

small, hollow cylinders that occur in pairs

Question 51

where are centrioles found?

Answer 51

in animals cells only, not in plant cells

Question 52

function of centrioles

Answer 52

play a role in cell division in animal cells

Question 53

similarities of animal and plant cells

Answer 53

both contain: - cell membrane - mtiochondria - nucleus - cytoplasm

Question 54

differences between plant and animal cell

Answer 54

chloroplast: - plant: chloroplasts are present in large number of photosynthetic cells - animals: chloroplast are absent centrioles: - plant: centrioples are absent - animals: centrioles are present vacuole: - plant: present as a single, large and central vacuole - animal: vacuoles are small and numerous