Chapter 2- Membranes and Cell Organelles Flashcards
Cell theory
All cells arise from pre-existing cells
Cells are the basic functional unit of life
All living things are composed of cells and the products of cells
o Cells –> tissue –> organ –> organ system –> organism
Cell
- Largely filled with water
- Separated from external water by an insoluble membrane
- Need to:
o Remove wastes
o Produce energy for chemical reactions
o Take in nutrients for REACTIONS
o Export useful items
o Grow + reproduce - Cells are limited by their size, and they divide when too big
o They need to be small to maintain large SA:V
o Increasing SA:V- staying small, highly folded inner membrane - All cells have cytosol, DNA, ribosomes, and a plasma membrane
Prokaryotes
- No membrane bound organelles BC cell is too small
- Have one chromosome which is circular
- Do have a cell wall
Eukaryotes
- Have many chromosomes which are linear
Plasmids
- Small rings of double stranded DNA
- They have much less DNA chromosomes
Apoptosis
Programmed cell death
Generally balanced by cell reproduction (in fully formed tissue)
Unbalance leads to:
o An increase in cells –> tumour develops –> cancer
o A decrease in cells –> degeneration
Caused by:
o Mitochondrial pathway (inside the cell)
When: serious damage occurs inside the cells or a virus
What: proteins break down mitochondrial membrane, which then causes apoptosis
o Death receptor pathway (outside the cell)
When: not fully developed, excess cells, no longer needed
What: cell shrinks, gets broken down whilst parts are preserved, and then broken down or recycled
Staining
Helps identify positions of regulator proteins within cells
o These proteins determines whether a cell lives or dies
Necrosis
Uncontrolled cell death
Occurs if cell has suffered chemical or mechanical trauma, which results in damage to the plasma membrane
Death is messy and affects surrounding cells
Cytoplasm
Cytoplasm = cytosol + all organelles except the nucleus
Protoplasm
Protoplasm = cytosol + all organelles
Plasma membrane
Present: all cells
Function: controls the entry of dissolved substances into and out of the cell
Structure:
o Pliable
o Phospholipid bilayer with protruding proteins + glycoproteins
Some of these proteins form channels that allow for passive and active transport (fluid mosaic model)
Is a bilayer because the hydrophobic lipid must associate with a lipid, and can’t associate with water
The phospholipids are not bound (not a polymer)
o Semipermeable/partially permeable/differentially or selectively permeable
o Has cholesterol throughout it, which adds flexibility
Glycoprotein
Any naturally occurring compound where carbohydrate side chains are bonded to protein
E.g. certain enzymes and hormones, and various antigens (on plasma membrane)
Antigens
Location: outer surface of plasma membrane
Function:
o Recognises ‘self’ and ‘non-self’/’foreign’ cells
o Important defence mechanism against bacterial infection
Structure:
o Protein combined with carbohydrate
o Differs between organisms (even of the same species)
Diffusion
Definition: The passive net movement of a substance from and area of high concentration to an area of low concentration
Substances: small hydrophobic molecules (e.g. O2, CO2, steroids) + small uncharged hydrophilic molecules (alcohol, urea)
Involves: phospholipid bilayer
Hydrophilic
Polar = water soluble = lipid insoluble = associates with water
Hydrophobic/lipophilic
Non-polar = water insoluble = lipid soluble = associates with lipids
Can cross plasma membrane easily
Facilitated diffusion
Definition: The passive net movement of a substance from and area of high concentration to an area of low concentration. Occurs only through specific protein channels embedded in the membrane
Substances: large, uncharged, hydrophilic molecules (e.g. glucose) + ions (e.g. salts)
Involves: specific protein channels
Osmosis
- Definition: When water moves through a semipermeable membrane from a low solute solution (high concentration of water) to a high solute solution (low concentration of water). No energy is required.
- Other terms relating to osmosis:
o Isotonic: two solutions of the same concentration of solutes t/f no overall/net movement of water (water will still move, but at an even rate)
o Hypotonic: lower solute solution t/f has a high concentration of water molecules. The cell would burst if it was an animal cell, or become turgid if it was a plant cell (vacuole is full) as they have cell walls preventing the bursting
o Hypertonic: higher solute solution t/f lower concentration of water molecules. An animal cell would shrink or crenate. A plant cell would be plasmolysed or flaccid. - Substances: water
- Involves: phospholipid bilayer
Active transport
Definition: The net movement of substances from an area of low concentration to an area of high concentration. Requires energy in the form of ATP and specific protein channels
Substances: large, uncharged, hydrophilic molecules (e.g. glucose) + ions (e.g. salts)
Involves: specific protein channels
Bulk transport
Definition: For the movement of very large materials in bulk
Endocytosis:
o Bulk transport of material into a cell
Phagocytosis: solid material
Pinocytosis: liquid material
o Part of plasma membrane engulfs particles, forming a vesicle, which is then carried into cell
Exocytosis:
o Bulk transport of material out of a cell
o Vesicle within cytosol fuses with the plasma membrane, and vesicle contents are released out of the cell
Substances: protein hormones being released from a cell
Cell wall
Present: plants, fungi, and bacteria
Function:
o Gives strength and rigidity
o Maintains shape of cell
Structure:
o Primary cell wall: made of cellulose (plants), chitin (fungi)
o Secondary cell wall: made with the addition of lignin in some flowering plants, and adds elastic strength + support
Nucleus
Present: all eukaryotic cells
Function:
o Control centre
o Contains the genetic instructions for the production of proteins
Structure:
o Enclosed within the nuclear envelope (double membrane with pores)
o Has DNA dispersed throughout, which then become visible chromosomes during cell reproduction
Nucleolus
Location: within the nucleus
Synthesises + contains RNA
Adenosine triphosphate (ATP)
Compound in which useable energy (for cells) is chemically present
Is constantly being used up and must be replaced
Produced during cellular respiration
Mitochondria
Present: all eukaryotic cells Function: o To produce ATP by aerobic respiration o Powerhouse of the cell Structure: outer membrane + highly folded inner membrane (where ATP is produced)
Ribosomes
Present: all cells
Function:
o Site of protein synthesis
o Examples of protein synthesis:
Human red blood cells- make haemoglobin (oxygen-transporting protein)
Pancreas cells- make insulin (hormone, small protein)
Muscle cells- make actin + myosin (contractile proteins)
Structure:
o Not membrane-bound
o Can be attached to rough endoplasmic reticulum or free in cytosol
o Composed of rRNA and protein
Endoplasmic reticulum
Present: eukaryotes Function: o Synthesise proteins o Transport materials within the cell Structure: o System of channels (channel walls are formed by membranes)
Golgi apparatus
Present: eukaryotes (prominent in cells that export proteins)
Function:
o Package + modify proteins for export
Lysosomes
Present: animal cells
Function:
o Destroy unwanted cell parts or damaged molecules inside or outside the cell by producing digestive enzymes
o Can be involved in apoptosis (e.g. removing zones of cells of embryonic human hands)
Structure:
o Sac-like structures
o Filled with fluid containing dissolved digestive enzymes
o Part of the cytoplasm
Peroxisomes
Present: animal and plant cells
Function:
o Prevent the accumulation of hydrogen peroxide (poisonous in excess)
o Detoxify various toxic materials in the bloodstream
Structure: contain the enzymes catalase and oxidase
Endosomes
Present: animal cells
Function: pass material (that has entered the cell through endocytosis) to lysosomes for digestion
Structure: membrane-bound
Chloroplasts
Present: plants, protists
Function:
o Convert light energy –> chemical energy
o Anabolic
o Site of photosynthesis
Structure:
o Double membrane (inner + outer)
o Inner membrane contains:
Thylakoid/lamella membranous sacs, and several of these form grana, which is where chlorophyll is located. Light dependant stage
Stroma, semi-fluid substance between grana, contains enzymes needed for light independent stage
Cytoskeleton
Present: all cells
Function:
o Maintaining the shape of a cell
o Used as a support structure for the organelles within a cell
o Movement of materials within a cell
o If needed, movement of the actual cell
Comprised of:
o Microtubules: hollow; made of sub-units of tubulin protein
o Microfilaments: solid, thinner, more flexible than above; made of actin
o Intermediate filaments: very tough; made of variety of proteins; tie into cytoskeleton of other cells
Occluding junctions/tight junctions
Present: animal cells
Function:
o TOF: Tight/Occluding prevention of Fluid transfer
o E.g. preventing fluid moving from your digestive system into your body
Not in plants because plants have pectin (sticky) to keep cells together
Anchoring junctions/desmosomes
Present: animal cells Function: o Keep cells together o E.g. heart muscle cells, skin cells Not in plants because plants have pectin (sticky) to keep cells together
Gap junctions/communicating junctions
Present: animal cells
Function:
o Allows cells to communicate without having to go through proteins (through channels)
o Allows substances through
o Allows molecules + ions to pass through
Scientific method
- Hypothesis:
o A cause (independent variable) + effect (dependent variable)
o Use: “That/if ‘x’ is increased/decreased, then ‘y’ will happen/increase/decrease”
o E.g. That light exposure will increase the rate of O2 bubbles produced (indicating increased rate of photosynthesis) - Aim:
o Use: “To investigate the effect of…” OR “To investigate whether…” - Control + experimental group: one without IV, one with. Needed for comparison to measure effect of IV
- Sample size: 20-100 individuals in each group
- Controlled variables:
o Use: at least 2 factors that must be kept the same that are specific and different to those used in the questions
o E.g. same species, temperature, amount of water, same age, etc. - State DV
- Expected results:
o Can include diagrams
o Use: “Hypothesis would be supported/rejected if…” - Experiments should be REPEATED to increase amount of data + increase validity of conclusions
- In questions do: IV, SS, CV, DV, Repeat experiment
How are organelles beneficial?
- Large SA:V (highly folded inner membranes) t/f adequate quantities of substances can enter + leave cell
- Different chemical reactions can happen at the same time without interference
What is the order of cell structures of their use in protein synthesis?
- Nucleus –> rough endoplasmic reticulum –> Golgi body –> vesicles
Chromatin
- Unwound chromosomes
- Loose DNA with protein
