Cell structure Flashcards
Cell theory
- All living things are made of cells
- Cells are the basic unit of life
- All cells come from pre-existing cells
Prokaryote vs Eukaryote (In terms of nucleus, organelles and number of cells)
Prokaryote - no cell nucleus, always unicellular, does not contain membrane bound organelles
Eukaryote - has a cell nucleus, can be uni or multi cellular, contains membrane bound organelles
Typical components of prokaryotes (6 things)
- Cell wall
- Plasma membrane
- 70S ribosomes
- Cytoplasm
- Plasmids
- Naked DNA in a loop (In nucleoid)
70S vs 80S ribosomes
70S - found in prokaryotes, smaller, lighter
80S - found in eukaryotes, larger, higher mass
Function of cell wall (3 points)
1) Maintain cellular structure
2) Prevent cell from bursting when osmotic pressure is higher inside cell
3) Protects against toxins
Function of plasma membrane (2 points)
1) Controls what enters and exits the cell
2) Separates cells interior from external environment - maintains internal chemistry
Function of cytoplasm (2 points)
1) Suspends contents of cell (e.g. ribosomes, ions, organic molecules)
2) Acts as a site for metabollic reactions
Function of ribosomes (1 point)
1) Synthesising proteins through translation
Function of Naked DNA in prokaryotes (2 points)
1) Contains information for protein synthesis
2) Expressing genes in replication
Funtion of plasmids in prokaryotes (1 point)
1) Contains pieces of DNA which can be transfered to other prokaryotic cells through horizontal gene transfer
Typical components of Eukaryotes (12 things)
1) Plasma membrane
2) Cytoplasm
3) Nucleus
4) Mitochondria
5) Golgi apparatus
6) 80S ribosomes
7) Smooth endoplasmic reticulum
8) Rough endoplasmic reticulum
9) Vacuole
10) Cytoskeleton
11) Vesicle
12) Lysosomes
Function of mitochondria (1 point)
1) Double membrane bound organelles which convert glucose to ATP through respiration
Function and structure of Nucleus (3 points)
1) Contains DNA associated with histone proteins and is organised into chromosomes
2) Contains nucleolus, which produces ribosomes
3) Has a double membrane which contains nuclear pores - allows small molecules like RNA, glucose and ions to pass through
Function of SER (1 point)
1) Produces and stores lipids, including steroids
Function of RER (1 point)
1) Has ribosomes attached to surface which produce proteins
Function of Golgi apparatus (1 point)
1) Process and package proteins, which are released in golgi vesicles
Function of vesicles (1 point)
1) Small sac which transports and releases substances made in the cell by fusing with cell membrane
Function of vacuole (2 points)
1) Acts as a store for substances
2) Maintains osmotic balance in cell
What is cytoskeleton composed of and what is its function?
1) A system of protein fibres called microtubles and microfilaments
2) Help to hold organelles in place and maintain structure of cell
Compartmentalisation
The process by which organelles are packaged into membranes to allow interiors to have different conditions to rest of cytoplasm
Advantages of compartmentalisation (4 points)
- Metabolites (substances involved in metabolism) and enzymes are closer so higher chances of successful collision
- Damaging substances e.g. toxins can be isolated and expelled so they don’t spread
- Areas of membranes can be dense in certain proteins to increase efficiency of specific proccess
- Can maintain conditions e.g. temp and pH for a specific reaction and enzyme
Structure of phospholipids (found in membranes)
- Two layers of phospholipids
- Outer layer = hydrophilic head face outwards and hydrophobic tails face inwards
- Inner layer = hydrophobic tails face inward towards other tails and hydrophobic heads face towards interior of cell
2 examples of unicellular organisms where processes of life can be studied
Parecium - eukaryote
Chlamydomonas - eukaryote
How do parecium and chlamydomonas exchange matter with environment?
Parecium - waste products excreted through anal pore
Chlamydomonas - oxygen from photosynthesis diffuses out of cell membrane
How do parecium and chlamydomonas obtain energy and matter?
Parecium - eats small unicellular organisms
Chlamydomonas - is an autotroph so uses photosynthesis to obtain energy
How do parecium and chlamydomonas carry out metabolic reactions?
Cells contain enzymes to catalyse reactions - in cytoplasm for both and also chloroplasts only in chlamydomonas
How do parecium and chlamydomonas grow?
Both grow until maximum surface area to volume ratio, then they divide
How do parecium and chlamydomonas respond to their environments?
Parecium - controls cilia beating to move according to enviroment
Chlamydomonas - Light sensitive eye spot allows them to sense light and move towards it using flagella
How do parecium and chlamydomonas reproduce?
Both - nucleus divides via mitosis to reproduce asexually. Two can also fuse before dividing to carry out sexual reproduction
How do parecium and chlamydomonas maintain homeostasis?
Both - excess water collected to a contractile vacuole and expelled to maintain osmotic pressure
Describe features of striated muscle fibers that make them an atypical cell.
Eukaryotic cell which contains more than one nucleus
Describe features of red blood cells that make them an atypical cell.
Eukaryotic cell which doesn’t have a nucleus (in adults)
Describe features of aseptate fungal hyphae that make them an atypical cell.
Has continuous cytoplasm and is not clearly divided into individual cells
Describe features of phloem sieve elements that make them an atypical cell.
- No nucleus
- Little cytoplasm
- Few organelles
What is the cell wall made of in fungi, plants and bacteria cells?
Fungi - chitin
Plants - cellulose
Bacteria - peptidoglycan
What are the advantages of compartmentalisation of nucleus?
- Post transcriptional modifications can occur (parts of mRNA are removed after transcription before it leaves nucleus)
- Allows cytoplasm to send ligands (i.e. hormones) to nucleus and tell it to produce more or less specific proteins depending on conditions
Which organelles have a double membrane in eukaryotic cells?
- Nuclei
- Mitochondria
- Chloroplasts
Which organelles have no membrane?
Ribosomes, centrioles, nucleolus
Which cell structures are not considered organelles?
Cytoplasm, cytoskeleton, cell wall
How were cell components first separated?
1) Cells disrupted with a homogeniser (blender)
2) Centrafuged step by step, removing the pellet between each centrafuge. The centrafugal force increases each time to separate less dense organelles
Lysosomes
Organelles which hydrolize biological polymers and contain high concentration of enzymes.
What is an example of compartmentalisation in eukaryotic cells and how it is beneficial?
Lysosomes contain acid hydrolases (enzymes which hydrolize molecules and work best in acidic pH) so interior is maintaned at 5 pH by actively producing H+ ions
Acidic interior protects against uncontrolled digestion of cytoplasm - even if membrane breaks down acid hydrolase would not work in neutral pH of cytoplasm
How does compartmentalisation benefit phagosome (phagocytic vacuole)?
- When a cell engulfs a particle, it encloses it in a phagosytic vacuole
- which fuses with a lysosome to form a phagolysosome
- it is then digested by hydrolitic enzymes
How are outer and inner membranes, cristae, IM space and matrix adapted to their functions within the mitochondria?
Outer membrane - has transport proteins to move key materials for respiration
Inner membrane - has ETC and ATP synthase
Cristae - folds increase SA:Vol ratio
IM space - small space maximises electrochemical gradient in ETC
Matrix - contains specific enzymes for Krebs
How are thylakoids, Grana, photosystems, stroma and lamellae adapted to their functions witin chloroplasts?
Thylakoids - small internal volume to maximise electrochemical gradient
Grana - thylakoid aranged into stacks to increase SA:Vol of membrane
Photosystems - pigments organised into photosystems in thylakoid to maximise light absorption
Stroma - central cavity contains appropriate enzymes and pH for Calvin cycle
Lamellae - connects grana to maximise photosynthesis efficiency
What are the components of the nucleus?
Nuclear envelope made of a double membrane with nuclear pores in it, Nucleoplasm, Chromatin (looks like a ball of hair made of DNA), nucleolus.
What are the two ways that substances can be released from the golgi apparatus?
Constitutive secretion - released immediately in a vesicle
Regulatory secretion - strored in secretory vesicles for a sustained release triggered by ligand binding to specific receptor
What are vesicles?
Membrane - wrapped containers which transport materials
How does clathrin aid in the formation of vesicles?
- Protein coat which forms a lattice around a part of the membrane with the substance to be transported
- Causes it to fold and wrap into a vesicle
- Once vesicle is formed, clathrin dissociates
What is receptor mediated endocytosis?
Substance which needs to be transported into cell acts as a ligand and activates adaptor proteins which cause clathrin to bind and vesicle formation to begin.
Function and structure of ligaments
Connects bone to bone - elastic to allow for movement
Function of synovial fluid
Fluid found between bones which acts as a shock absorber
What are joints?
Site of junction between two or more bones
Function and structure of tendons
Attaches muscle to bone and are inelastic
