C3 Cell Structure Flashcards
Eukaryotes
These are (mostly) multicellular organisms made up of eukaryotic cells like animals, plants, fungi, and protists.
Prokaryotes
These are single-celled organisms made up of prokaryotic cells like bacteria.
Organelles found in a typical animal cell
- Cell Membrane
- Nucleus
- Mitochondria
- Endoplasmic Rectilium(smooth and rough)
- Golgi Apparatus
- Lysosome
- Ribosome
Nucleus Structure
Controlling the cell’s activities - The DNA contains instructions to produce proteins
1. Nuclear Envelope - Double membrane; outer membrane has ribosomes on its surface; controls entry and exit of substances out of the nucleus
2. Nuclear Pores - allows the passage of larger molecules
3. Nucleoplasm - makes up bulk of nucleus (the inside)
4. Chromatin, which is the form chromosomes take when not dividing, and these contain DNA - protein bound, linear DNA
5. Nucleolus - spherical region within the nucleus, makes ribosomal DNA and assembles them (can be more than one)
Cell Membrane
Found on the surface of animal cells - controls what enters and leaves the cell.
Fluid - phospholipids can move
Cell signalling - Receptors can detect signals from other cells
Phospholipid Bilayer
Mitochondria
Site of aerobic respiration
Has a Double Membrane; the inner membrane is folded to make extensions called cristae - provides large surface area for enzymes and proteins involved in respiration to attach
The matrix makes up the remainder of the mitochondrion, containing ribosomes and DNA; allows the mitochondria to manufacture their own proteins, also many enzymes used in respiration are found in the matrix.
Ribosomes
- Site of protein synthesis
- Involved in the process of translation Two sizes: 80s (eukaryotic) 70s (prokaryotic + smaller)
- Made of two sub units, one large and one small.
Golgi Apparatus
Stack of membranes that make up flattened sacs (cisternae) with hollow structures.
Proteins are passed through to be modified and added to other molecules.
Labels proteins to be transported to their correct destination (transported in Golgi Vesicles to the cell surface to fuse with the membrane to release contents to the outside).
Stores lipids and proteins
Lysosomes
- Lysosomes are vesicles produced by the Golgi apparatus that contain hydrolytic enzymes.
- Digests worn-out organelles so useful chemicals can be reused.
- Breaks down dead cells (autolysis).
- Releases to the outside of the cell (exocytosis) to destroy material around the cell
Endoplasmic Reticulum
- Contains a system of membranes enclosing a fluid-filled space, known as cisternae.
- R(rough)ER
1. Provide large surface area for the synthesis of proteins and glycoproteins [the proteins are made using the ribosomes (that are on the outer surface of the cisternae)]
2. Provides a pathway for materials throughout the
cell i.e. proteins - S(smooth)ES
1. Synthesis, storage, and transport of lipids and carbohydrates.
Cell Wall Properties
- Supports the cell - The contents of the cell press against the cell wall to make it rigid.
- Prevents the cell from bursting - The cell wall can withstand high osmotic pressure.
- Allows exchange of substances between cells.
- Made up of cellulose.
- Contains channels (gaps) known as plasmodesmata (or plasmodesma if just one).
Chloroplasts
Site of photosynthesis - These reactions take place in the grana and stroma.
- Thylakoid - fluid-filled sacs that contain chlorophyll; where 1st stage of photosynthesis takes place.
- Grana - 100 thylakoid; ech thylakoid contins chlorophyll
- Stroma - fluid-like matrix where the 2nd stage of photosynthesis takes place.
- DOUBLE MEMBRANE
Vacuole
- Helps to maintain pressure within the cell, which keeps the cell rigid and stops the plant from wilting.
- tonoplast - the membrane around the organelle
- Contains cell sap (solution of salt and sugars).
Algae
- Contain the same organelles as plant cells.
- Contain chloroplasts with different shapes to those found in plant cells.
- CELL WALL made of cellulose and/or glycoprotein
Fungi
Contain most of the organelles found in plant cells. Do not contain chloroplasts. Cell walls made up of chitin rather than cellulose.
Specialised cells
These are cells with certain features that allow them to carry out a particular function.
Tissue
This is a group of similar cells working together to carry out a particular function.
Organ
This is a group of tissues working together to carry out a particular function.
Organ system
This is a group of organs working together to carry out a particular function.
Examples of animal tissues
- SQUAMOUS Epithelial tissue - sheets of cells; that line organs and have protective functions.
- CILIATED epithelium - lines organs such as the trachea where it can sweep mucus away from the lungs; made up of ciliated epithelial cells and goblet cells. The goblet cells release mucus to trap pathogens, whilst the ciliated epithelial cells use cilia to sweep the mucus away.
Examples of plant tissues
- Xylem - transports water, and mineral ions through the plant; made up of dead xylem vessel cells which have no end walls and no organelles.
- This forms a continuous column through which water can flow.
- The walls of these cells are strengthened by a waterproof material known as lignin.
Prokaryotic Cell Structure
- SLIME CAPSULE - protects bacterial cells from other cells & helps bacteria stick together for protection.
- PILI - used for attaching to other cells or surfaces.
- FLAGELLA - assist the cell in movement.
- PLASMID - extra genes tp aid in survival (eg for antibiotic resistance) found in smaller loops.
- MUREIN - makes up cell wall
Comparing prokaryotes and eukaryotes
- P; no nucleus E; contains nucleus
- P; circular DNA free in cytoplasm E; DNA enclosed in nucleus, linear
- P; DNA bound to proteins E; DNA not associated w/ histones/proteins
- P; no membrane-bound organelles E; contains membrane-bound organelles
- P; ribosomes size 70s E; ribosomes 80s
- P; MUREIN cell wall E; plants have cellulose, fungi have chitin cell wall
What do Prokaryotes, Mitochondria and Chloroplasts have in common?
- 2 circular strands of DNA
- 70S ribosomes
What do the similarities between Prokaryotes, Mitochondria and Chloroplasts mean?
mitochondria may have evolved from prokaryotes OR eukaryotes have engulfed a prokaryote forming an endosymbiotic relationship and evolving into mitochondria
Virus Structure
- Always present:
- Genetic material - Viral genomes may be DNA or RNA and single or double-stranded.
- Capsid - A layer of protein molecules that surrounds and protects the genetic material.
- Sometimes present:
- Lipid Envelope - An outer layer made up of phospholipids (only present in some viruses).
- Attachment proteins - Also known as surface, attachment, or envelope proteins, these help viruses bind to host cells.
- Enzymes - Some viruses carry enzymes, like reverse transcriptase, which allows them to convert RNA into DNA.
Resolution
measure of microscope’s ability to distinguish 2 points which are close together on an object
Transmission electron microcope
Uses electromagnets to transmit a beam of electrons through a specimen. The denser parts absorb more electrons, so appear darker in the image formed.
Scanning electron microscope
Scan a beam of electrons across the surface of a specimen. Reflected electrons are then used to form an image.
Artefacts
residue/ anything we are not viewing
Difference between microcopes
- S; no thin specimen (but still will be dead) T; thin specimen required (therefore specimen will be dead) O; specimen can be alive
- S; electron beams bounce off the surface of the specimen T; electron beam penetrates the specimen; allowing us to see internal structures
- S; 3D images T; 2D images
- S; less complex staining process T; complex staining process O; complex staining process
- S; image may contain artefacts T; no artefacts
- S+T; black + white images O; colour images
- S+T; higher resolution than O (light has longer wavelengths than electrons)
Why must the solution be ICE-COLD during ultracentrifugation?
To reduce enzyme activity that might digest organelles
Why must the solution be ISOTONIC during ultracentrifugation?
To prevent the organelles from bursting/ shrinking due to osmosis
Why must the solution be BUFFERED during ultracentrifugation?
To keep the pH constant and prevent the denaturing of enzymes
Cell Fractionation
The process of seperating cell organelles from each other
Homogenise
1st step of cell fractionation: Breaking up of cells - grinds up cells or vibrates; breaks plasma membrane
Filtration
2nd step of cell fractionation: filtering cell debris/ unbroken cells from the organelles
Ultracentrifugation
3rd step of cell fractionation: supernatant is centrifuged (spun) at high speeds so heavier organelles will collect at the bottom of the tube to be removed
Pellet
Thick sediment @ the bottom of the tube; contains heavier organelles
Supernatant
Rest of the lighter organelles that are suspended in the solution above the pellet
Weight order of organelles
- Nucleus
- Chloroplasts
- Mitochondria
- Lysosomes
- Endoplasmic Reticulum
- Ribosomes
Mitosis
Divison of a cell that results in each of the daughter cells having the same number of chromosomes as the parent cell and each other
G1 (First Gap Phase)
The cell grows larger, and copies organelles
S Phase
- Step 2 of Interphase
- Synthesises a copy of the DNA in it’s nucleus and duplicates centrosome
[Centrosome: pulls chromatids apart. The core structure us made up of two centrioles aligned perpendicularly. The rest of the structure is the spindle fibres]
G2 (Second Gap Phase)
Cell grows more, makes proteins and organelles, and begins to rearrange contents for mitosis again; G2 ends when mitosis begins
INTERPHASE
Occupies most of the cell cycle; sometimes known as resting phase due to no division taking place
NUCLEAR DIVISION
When the nucleus divides into two (mitosis) or four (meiosis)
CYTOKINESIS
After/ follows nuclear division and is the process by which the cytoplasm divides to produce 2/4 new cells; part of TELOPHASE
