Cells Chapter 1 and 2 Flashcards
Organisms - living things
Energy source
Liquid water
Chemical building blocks – C, H, 0, N required for cellular repair, growth and reproduction
Stable environmental conditions
Cells
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
Cell variety
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
CELLS: WHY SO SMALL?
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
Surface area: volume ratio
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
what is an organism
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
What are prokaryotes?
Smallest living cells (2µm in diameter)
Unicellular
Bacteria cells
Have simple internal structure
No membrane bound nucleus
No membrane bound organelles
No cytoskeleton
Eukaryotic cells
Much bigger 10µm - 100µm
Multicellular
Complex internal structure
Membrane bound organelles
Nuclear envelope
Cytoskeleton
Cell wall present in some
Organelles
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.
what does membrane-bound mean
When organelles are membrane-bound, this means they have a membrane around them that controls what enters and exits that organelle.
membrane-bound organelles factors
nucleus
rough er
smooth er
Golgi body
lysosomes
mitochondria
chloroplasts
vacuoles
vesicles
non-membrane-bound organelles factors
ribosomes
cell wall
cytoskeleton
plasma membrane
Cytoplasm
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
Cytosol
Found in eukaryotic and prokaryotic cells
Structure:
Fluid component of the cytoplasm
Function:
Site of cellular activities
Cytoskeleton
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
Ribosomes
Found in both eukaryotic and prokaryotic cells
Structure:
No membrane
Made up of rRNA (ribosomal RNA) and protein
Function:
The site of protein synthesis
Nucleus
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
Endoplasmic reticulum
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
Golgi apparatus
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
Mitochondria
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)
Chloroplasts
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
Vacuole
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
Lysosomes
Found in eukaryotic cells
Structure:
Single membrane
Function:
Digesting, recycling and breaking down old organelles, cells and food molecules
Cell walle
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
Comparison of plant and animal cells
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
Why do we have membranes around cells?
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
Structure of plasma membrane
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
Cell wall in comparison
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
PHOSPHOLIPID
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
Movement of substances
There are 4 main types of transport
Some are passive and some are active
Simple diffusion
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
Concentration gradient
Going down the concentration gradient means substances will move from higher concentration to lower
It will stop moving until both sides are equal
Facilitated diffuson
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
Active transport
Moves dissolved substances from a region of LOW concentration to HIGH (against the concentration gradient)
REQUIRE ENERGY (ATP)
Endocytosis/exocytosis
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
Function of plasma membrane
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
Osmosis
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
Tonicity
That the concentration of solutes dissolved in an extracellular solution can determine the direction and rate of osmosis
