Cells Chapter 1 and 2

Question 1

Organisms - living things

Answer 1

Energy source
Liquid water
Chemical building blocks – C, H, 0, N required for cellular repair, growth and reproduction
Stable environmental conditions

Question 2

Cells

Answer 2

Are the basic structural and functional units of life, all living organisms are built of one or more cells
They are microscopic 1µm = 0.001mm
They arise from pre-existing cells by cellular reproduction

Question 3

Cell variety

Answer 3

Cells vary in size and shape
The variety in shape and structure is related to their function
Microbial cells are 10x smaller than plant and animal cells

Question 4

CELLS: WHY SO SMALL?

Answer 4

Cells must always carry out variety of functions that are essential for life
Trapping a source of energy
Obtain building blocks required for cellular repair, growth and reproduction, taking up water and nutrients, removing wastes

Question 5

Surface area: volume ratio

Answer 5

L = Length of one side of the cube
SA = 〖6𝐿〗^2
V = 𝐿^3
As the cubes increase in size, volumes enlarge faster than SA
SA:V decreases as cube gets bigger
Higher the ratio = greater efficiency of 2-way exchange of materials across membranes

Question 6

what is an organism

Answer 6

An organism is defined as something that is living
Biotic (living) and abiotic (non-living)
Cells of plants, animals, bacteria and amoebas have the following four common factors
Genetic material
Cytosol
Ribosomes
Plasma membrane

Question 7

What are prokaryotes?

Answer 7

Smallest living cells (2µm in diameter)
Unicellular
Bacteria cells
Have simple internal structure
No membrane bound nucleus
No membrane bound organelles
No cytoskeleton

Question 8

Eukaryotic cells

Answer 8

Much bigger 10µm - 100µm
Multicellular
Complex internal structure
Membrane bound organelles
Nuclear envelope
Cytoskeleton
Cell wall present in some

Question 9

Organelles

Answer 9

the ultrastructure of plant and animal cells in terms of their organelles and identification of these organelles using the light microscope and electron micrographs (chapter 2)

Cells are made of different structures known as organelles that work together to increase the efficiently of the cell.

Question 10

what does membrane-bound mean

Answer 10

When organelles are membrane-bound, this means they have a membrane around them that controls what enters and exits that organelle.

Question 11

membrane-bound organelles factors

Answer 11

nucleus
rough er
smooth er
Golgi body
lysosomes
mitochondria
chloroplasts
vacuoles
vesicles

Question 12

non-membrane-bound organelles factors

Answer 12

ribosomes
cell wall
cytoskeleton
plasma membrane

Question 13

Cytoplasm

Answer 13

Found in eukaryotic and prokaryotic cells
All organelles (except nucleus) and the cytosol in which they float in make up the cytoplasm.
Structure:
Contents of the cell
Contains water, soluble materials and organelles
Function:
Site of cellular activities

Question 14

Cytosol

Answer 14

Found in eukaryotic and prokaryotic cells
Structure:
Fluid component of the cytoplasm
Function:
Site of cellular activities

Question 15

Cytoskeleton

Answer 15

Found in eukaryotic and prokaryotic cells
Structure:
Network of fibres that makes up the infrastructure of the cell
Made up of actin filaments, intermediate filaments and microtubules
Function:
Structural support
Movement of materials

Question 16

Ribosomes

Answer 16

Found in both eukaryotic and prokaryotic cells
Structure:
No membrane
Made up of rRNA (ribosomal RNA) and protein
Function:
The site of protein synthesis

Question 17

Nucleus

Answer 17

Found in eukaryotic cells
Structure:
Surrounded by a double membrane (phospholipid bilayer) called the nuclear envelope’ which has openings called nuclear pores
Contains chromosomes (DNA) and the nucleolus (where ribosomes are made)
Function:
Contains genetic information

Question 18

Endoplasmic reticulum

Answer 18

Found in eukaryotic cells only
Structure:
The Endoplasmic reticulum has a single membrane
Network of branching sacs
Rough E.R: contains ribosomes
Smooth E.R: contains enzymes for synthesising lipids
Function:
Rough E.R: protein synthesis
Smooth E.R: lipid synthesis

Question 19

Golgi apparatus

Answer 19

Found only in eukaryotic cells
Structure:
Single membrane
Contains receptors for the products of the rough endoplasmic reticulum
Stack of membrane bound sacs
Made up of a phospholipid bilayer
Function:
Packaging vesicles to transport proteins out of the cell

Question 20

Mitochondria

Answer 20

Found in eukaryotic cells
Structure:
Has a double membrane: an inner and an outer membrane
The folds of the inner membrane are called cristae
The fluid contained within the inner membrane is contained in the matrix
Function:
The site of aerobic cellular respiration (production of useable energy in the cell)

Question 21

Chloroplasts

Answer 21

Found in eukaryotic cells (plant cells only)
Structure:
Double membrane
Contains a pigment called chlorophyll which captures light energy from the Sun
Function:
Site of photosynthesis where the energy from the Sun is used to produce glucose which can be converted into energy

Question 22

Vacuole

Answer 22

Found in eukaryotic cells
Plant cells have a large vacuole
Animal cells have small vacuoles
Structure:
Single membrane
Components vary: pigments, oils, carbohydrates, water or toxins
Function:
Maintains cell structure (plant cells)
Act as temporary energy storage

Question 23

Lysosomes

Answer 23

Found in eukaryotic cells
Structure:
Single membrane
Function:
Digesting, recycling and breaking down old organelles, cells and food molecules

Question 24

Cell walle

Answer 24

Found in eukaryotic and prokaryotic cells (NOT in animal cells)
Structure:
Plant and algae cells: made up of cellulose
Fungi cells: made up of chitin
Prokaryotic cells: made up of peptidoglycan
Function:
Provides structure and mechanical strength

Question 25

Comparison of plant and animal cells

Answer 25

Plant and animal cells have common organelles
Plants have both mitochondria and chloroplasts and therefore can undergo cellular respiration and photosynthesis
Plants have a cell wall that aids with structural support but animal cells do not
Plant cells also have a permanent large vacuole for the storage of water, minerals and ions. Animal cells have small vacuoles that may not be permanent

Question 26

Why do we have membranes around cells?

Answer 26

Keep foreign molecules out
Exchange substances with the external environment
Without this boundary cells cannot survive and life wouldn’t exist
It selectively controls the entry and exit of materials – SEMIPERMEABLE

Question 27

Structure of plasma membrane

Answer 27

Phospholipid bilayer
Proteins embedded within and on surface
Hydrophilic – water-loving heads to the outside
Hydrophobic – water-hating tails on the inside
Having these properties allows the membrane to select what can enter and leave the cell

Question 28

Cell wall in comparison

Answer 28

Outermost layer in PLANTS, FUNGI and BACTERIA
Provides support and protection
Has no selective properties
Plants: Made of CELLULOSE (complex carbohydrate)
Fungi: Made of CHITIN (polysaccharide)
Bacteria: Made of long strands of POLYSACCHARIDES and AMINO ACIDS

Question 29

PHOSPHOLIPID

Answer 29

The hydrophilic heads are exposed at BOTH external environments
The hydrophobic tails face each other
Lipophilic/hydrophobic substances move freely through the phospholipid bilayer due to the hydrophobic nature of fatty acid tails
Water, gases and other small hydrophobic and polar molecules can diffuse directly
The plasma membrane is selective

Question 30

Movement of substances

Answer 30

There are 4 main types of transport
Some are passive and some are active

Question 31

Simple diffusion

Answer 31

Movement of substances across the phospholipid bilayer from a region of higher concentration to one of lower concentration
Going down the concentration gradient
NO ENERGY
When both sides are equal in concentration, diffusion stops
Small lipophilic substances move across easily

Question 32

Concentration gradient

Answer 32

Going down the concentration gradient means substances will move from higher concentration to lower
It will stop moving until both sides are equal

Question 33

Facilitated diffuson

Answer 33

Enables molecules that cannot diffuse across the phospholipid bilayer to move across it by transporter proteins
NO ENERGY
can be carrier proteins or channel proteins
Carrier proteins undergo structural changes when binding to a molecule and deliver it to the other side of the membrane

Question 34

Active transport

Answer 34

Moves dissolved substances from a region of LOW concentration to HIGH (against the concentration gradient)
REQUIRE ENERGY (ATP)

Question 35

Endocytosis/exocytosis

Answer 35

ENDO: solid particles taken INTO a cell
EXO: solid particles taken OUT of a cell
Bulk transport
A vesicle is formed using the membrane
PHAGOCYTOSIS: solid material
PINOCYTOSIS: fluid material

Question 36

Function of plasma membrane

Answer 36

1) Active and selective boundary
Separating cell from the external environment, allows passage of SOME substances
Active boundaries around organelles that help it maintain internal environments different from the cytosol
2) Denotes cell identity
Glycoproteins on the outside of the membrane act as cell markers
Each cell type has its own marker to help distinguish between self and foreign cells
3) Receives external signals
Can be a hormone
Receptors on the outside of the membrane allows signals to bind to it
The cell can then carry out a response
4) Transports material
Allows some substances to cross directly through the phospholipid bilayer
Some need to go through protein

Question 37

Osmosis

Answer 37

Net movement of water across a semipermeable membrane from a solution of high water concentration to one of lower concentration ‘

HYPOtonic: lower solute concentration
ISOTONIC: equal solute concentration
HYPERtonic: higher solute concentration

Question 38

Tonicity

Answer 38

That the concentration of solutes dissolved in an extracellular solution can determine the direction and rate of osmosis