A2.2 cell structure (SL) Flashcards
What are the 3 basic principles of cell theory?
1) All living things are made of cells
2) Cells are the smallest unit of life
3) Cells come only from other cells
Define “magnification”
how much larger an object appears compared to its real size
Define “Resolution”
the smallest interval distinguishable by the microscope, which then corresponds to the degree of detail visible in an image created by the instrument
Define “Membrane”
a bilayer formed from phospholipids as a consequence of their hydrophobic and hydrophilic regions
Explain what a plasma membrane is
Every cell has a membrane barrier separating the interior from its surroundings
Define “cytosol”
the liquid part of the cytoplasm
Define “cytoplasm”
Gel-like fluid substance made of water and many dissolved solutes such as salts, fatty acids, sugars, amino acids and proteins e.g. enzymes (needed to carry out the metabolic processes required to keep the cell alive; if these molecules not dissolved in water → not able to perform their function)
What is the relationship between solutes, solvents and solutions? Give examples for each.
Solute + Solvent = Solution
- solute e.g. glucose, oxygen
- solvent e.g. water
- solution e.g. glucose solution
What is evidence of universal common ancestry?
The use of the DNA code across all forms of life (today all living organisms use DNA as the genetic material)
Differences between prokaryotic and eukaryotic DNA?
Prokaryotic DNA is not in a nucleus and does not wrap around histone proteins
- if taken out, its a loop
Eukaryotic DNA is found in the cell nucleus and wraps around histone proteins
- if taken out, can be stretched until it becomes linear (straight line)
Nucleosome is DNA wrapped around how many histone proteins
8
Nucleosome is DNA wrapped around 8 histone proteins
only eukaryotes have histones because their DNA is longer than prokaryotes
Why can’t prokaryotes carry out aerobic respiration?
Because they don’t have mitochondria
Explain what exocytosis is (not definition)
Export of things outside the cell
Using vesicles
Define “Organelles” + examples
membrane bound units that compartmentalised functions in the cell
e.g. nucleus, mitochondria
only eukaryotes have them, not prokaryotes
Why compartmentalise?
1) Control concentrations of chemicals that are needed or produced by the organelles in their metabolic reactions
2) mRNA can be modified after transcription before it leaves the nucleus
3) Avoid enzymes (e.g. lysozymes in lysosomes from destroying the cell. It also allows phagocytic vesicles to be formed.)
Why does lysosome need to be bounded by a cell membrane?
- because it contains enzymes
- will digest organelles e.g. ribosomes, mitochondria
- killing cells from within :(
What is the function of Golgi Apparatus?
- The Golgi modifies polypeptides into their functional state
- The Golgi sorts, concentrates and packs proteins into vesicles
Vesicles of Golgi Apparatus are dispatched to?
- within the cell, to organelles called lysosomes
- the plasma membrane of the cell
- secretion to the outside of the cell via exocytosis
fuses with the plasma membrane & released out of the cell
Function of cytoskeleton
- Helps cells maintain their shape, organises cell parts and enables cells to move and divide
List the components that work together to form the cytoskeleton and their functional use
- Microtubules (movement)
- Actin filaments (movement)
- Intermediate filaments (structural)
What is the name of the polymers of a protein which forms part of the cytoskeleton
tubulin
polymers of a protein called tubulin and form part of the cytoskeleton
Function of microtubules
Used for intracellular transport of organelles and the separation of chromosomes during mitosis
Describe the structure of Centrioles (MTOC)
paired cylindrical-shaped organelles composed of nine groups of three microtubules organised with radial symmetry
What is the function of Centrioles/MTOC (microtubule organising centre)
- arrangement of the mitotic spindle during cell division
- serve as anchor points for microtubules in the cytoplasm and for cilia and flagella (when modifiied to become a basal body)
What is cilia?
- extensions from the cell surface which aid in cell movement
How are cilia formed?
formed from modified centrioles called a basal body
How does cilia work?
- Cilia beat in coordination with each other
- back and fourth beating
How do you tell apart cilia and flagella from their protrustions?
Flagella: If protrusions are longer and less numerous (usually only one or two)
Cilia: if the protrusions are short and numerous
How to flagella move?
flagella moves independently from each other
Describe the motion of sperm movement?
Sperm: propeller-like motion (spiral)
Give 3 examples of single membrane organelles
- lysosome
- ER
- golgi
Give 3 examples of double membrane organelles
- chloroplasts
- nucleus
- mitochondrion
What is chromatin?
Form of chromosome before it divides
Function of nucleolus
makes ribosomes
What are nuclear pores?
nuclear pores can be open and shut → can control when mRNA goes out
mRNA copied from DNA to go out of ribosome
pores needed for mRNA to pass through
(on the surface of the nucleus)
Define “Plastids”
Plastids: A family of organelles with two outer membranes and internal membrane sacs
Define “Cell wall”
Cell wall: a rigid layer outside the plasma membrane to strengthen and protect the cell
Vacuole: A flexible fluid-filled compartment surrounded by a single membrane
Centrioles: Cylindrical organelles that organise the assembly of structures composed of microtubules
Undulipodia: Cilia and flagella used to generate movement of a cell or movement of fluid adjacent to a cell
Define “Vacuole”
Vacuole: A flexible fluid-filled compartment surrounded by a single membrane
Define “Centrioles”
Centrioles: Cylindrical organelles that organise the assembly of structures composed of microtubules
Define “Undulipodia”
Undulipodia: Cilia and flagella used to generate movement of a cell or movement of fluid adjacent to a cell
Explain the meaning of “septate” and an example of an organism with this feature
multinucleated (more than one nuclei in one cell)
example: Aseptate fungal hyphae
Explain the cell structure and function of RBCs
- No nucleus = more space to carry haemoglobin (for oxygen)
- Biconcave / flattened disc shape
- Diffusion: O2 in, CO2 out
What is an alternate name of RBCs?
Erythrocyte
Give examples of eukaryotes that have atypical cell structures
- Aseptate fungal hyphae
- Skeletal muscle (striated muscle)
- RBC
- Phloem sieve tube elements
What is the function of flagellum?
movement
Name the parts of a prokaryotic cell
Functions of prokaryotic cell parts
- Flagellum
- Ribosomes
- Pilli
- Cell wall
- Cytoplasm
- Nucleoid
- Plasma membrane
What is the function of ribosomes?
protein synthesis
What is the function of pilli?
attachment, DNA transfer
What is the function of cell wall?
protective coating, can be Gram-positive or Gram-negative
Peptidoglycan → chemical that is different in gram positive and gram negative cell wall of Bacteria
- gram positive
- thick layer of Peptidoglycan- gram negative
- thin layer of Peptidoglycan
- also has outer membrane beyond the Peptidoglycan
- gram negative
What is the function of cytoplasm?
contains enzymes for metabolism
What is the function of nucleoid?
region containing closed-loop DNA
What is the function of plasma membrane
controls entry and exit of substance
What don’t prokaryotes have mitochondria?
- prokaryote → no organelles
- also don’t need mitochondria bc use anaerobic respiration
Describe the shape of Bacillus (bacteria)
rod shaped
Define “homeostasis” and give an example
iving organisms keep their internal environments within a certain range (they maintain a stable internal condition), despite changes in their external environment
e.g. by keeping concentrations of water and minerals within certain levels
Define “metabolism”
the sum of all the chemical reactions in a cell
Why are viruses not considered self-sustaining life? (link to metabolism)
Viruses lack metabolism, a reason they are not considered to self-sustaining life
Define “anabolic reaction”
smaller molecules join to make larger ones → use energy, endergonic
Define “catabolic reaction”
large molecules are broken down into smaller ones → release energy, exergonic
Explain what a catalyst is
speeds up chemical reaction by reducing the activation energy and it does not get used up
Define “nutrition”
all life obtains energy and matter
Define “autotrophs”
use external energy sources (usually the sun) to synthesise carbon compounds from simple inorganic substances
Define “heterotrophs”
use carbon compounds obtained from other organisms to synthesise the carbon compounds that they require
Give an example of a phototroph
photoautotroph → plants
- photo = light
Give an example of a chemoautotroph
- chemo = chemical
- e.g. volcanos under the sea, bacteria who live down there use energy from deep vents
Define “movement”
adaptions for movement are a universal feature of living organisms
What do sessile organisms refer to?
organisms that stay in one place
What do motile organisms refer to?
organisms that are mobile
Define “excretion”
a process in which metabolic waste is eliminated from an organism
Give an example of excretion in humans
primarily occurs via lungs and kidneys
- co2 created by both aerobic & anaerobic respiration
- aerobic: oxygen + glucose → water + carbon dioxide
- anaerobic: glucose → lactic acid; lactic acid broken down by oxygen into water + carbon dioxide
Give an example of excretion in plants
- excretion occurs via leaves, roots and stem
- photosynthesis
Give an example of excretion in unicellular organisms
occurs through the cell membrane, which is one reason cells must have a large surface area to volume ratio
Explain what egestion is
removal of undigested food
Define “growth”
increase in the size and mass of an organism
Define “development”
is the transformation of the organism through its lifespan
What does “response to stimuli” mean
- all life can recognise and respond to changes in environmental conditions
- even single celled organisms can recognise what is going on around them, and respond to changes in the environment
State the types of receptors and what their stimuli is
chemoreceptors: chemical concentration of substances
baroreceptors: pressure
thermoreceptors: temperature
photoreceptor: light energy
How do sexual and asexual reproduction differ?
- Sexual reproduction: involves two parents and the fusion of haploid sex cells from each parent
- Asexual reproduction: involves only one parent (mitosis)
