Cell Biology - Prokarytic and Eukaryotic cells

Week 1

What’s in a Plants cell? (Eukaryotic)

• Cell membrane

• Cytoplasm

• Nucleus (and internal structures)

• Mitochondria (and internal structures)

• Ribosomes

• Rough endoplasmic reticulum

• Smooth endoplasmic reticulum

• Golgi apparatus

• Lysosomes

• Small vacuoles (may be present)

• Centrosome and centrioles (in most animal cells)

What’s in a plant Cell? (Eukaryotic)

• Cell wall

• Cell membrane

• Cytoplasm

• Nucleus (and internal structures)

• Mitochondria (and internal structures)

• Chloroplasts (in photosynthetic cells, and their internal structures)

• Rough endoplasmic reticulum

• Ribosomes

• Smooth endoplasmic reticulum

• Golgi apparatus

• Large permanent vacuole

What’s in a Bacteria cell? (Prokaryotic)

Cell wall

Cell membrane

Cytoplasm

Ribosomes

Circular DNA (free in the cytoplasm)

Plasmids (small rings of DNA, in some bacteria)

Flagellum (in some bacteria, for movement)

Slime capsule (in some bacteria, for protection)

Cell membrane

Structure: A phospholipid bilayer containing proteins and cholesterol (in animal cells).

Function: Acts as a selectively permeable barrier, controlling the movement of substances into and out of the cell. Membrane proteins also enable cell signalling and transport.

Cytoplasm

Structure: Cytosol containing enzymes, dissolved substances and organelles.

Function: Provides an environment for metabolic reactions, such as glycolysis, the first stage of glucose breakdown during respiration.

Nucleus

Structure: A double-membraned organelle containing DNA and a nucleolus.

Function: Stores most of the cell's genetic information. DNA is transcribed into RNA, helping regulate gene expression and cellular activities.

Mitochondria

Structure: Double-membraned organelles with an inner membrane folded into cristae and a central matrix.

Function: Produce ATP through aerobic respiration. The electron transport chain creates a proton gradient that drives ATP synthase during oxidative phosphorylation.

Ribosomes

Structure: Complexes composed of ribosomal RNA (rRNA) and proteins.

Function: Synthesise proteins by translating messenger RNA (mRNA) into a sequence of amino acids.

Rough endoplasmic reticulum (RER)

Structure: A network of membrane-bound sacs with ribosomes attached to the surface.

Function: Synthesises and processes proteins destined for secretion, membranes or certain organelles. It also assists protein folding and quality control.

Smooth endoplasmic reticulum (SER)

Structure: A network of membrane-bound tubules without attached ribosomes.

Function: Synthesises lipids, helps detoxify certain compounds and stores calcium ions involved in cellular signalling.

Golgi apparatus

Structure: Stacks of flattened membrane-bound sacs called cisternae.

Function: Modifies, sorts and packages proteins and lipids into vesicles for transport to specific destinations.

Cell wall (Plant structure)

Structure: A rigid extracellular layer composed mainly of cellulose, hemicellulose and pectin.

Function: Provides mechanical strength, maintains cell shape and resists osmotic swelling when water enters the cell.

Chloroplast (Plants)

Structure: Double-membraned organelles containing chlorophyll, thylakoids and stroma.

Function: Carry out photosynthesis. Light energy is converted into chemical energy, which supports the production of carbohydrates from carbon dioxide.

Large permanent vacuole (Plant)

Structure: A large fluid-filled compartment surrounded by the tonoplast membrane.

Function: Stores water, ions and other substances. Water uptake generates turgor pressure, keeping plant cells firm and supporting growth.

Lysosomes (Animal)

Structure: Membrane-bound compartments containing hydrolytic digestive enzymes.

Function: Break down macromolecules, pathogens and damaged organelles into smaller components that can be recycled by the cell.

Centrosome (Animal)

Structure: A microtubule-organising centre containing pericentriolar material and usually two centrioles.

Function: Organises microtubules and helps form the mitotic spindle, which separates chromosomes during cell division.

Centrioles (Animal)

Structure: Cylindrical structures generally composed of nine groups of microtubule triplets.

Function: Help organise microtubules and can form basal bodies that organise cilia and flagella.

Cell wall

Structure: Usually contains peptidoglycan, a mesh-like network of sugars cross-linked by short peptides.

Function: Maintains cell shape, provides mechanical protection and prevents osmotic lysis.

Cell membrane

Structure: A phospholipid bilayer containing transport proteins and enzymes.

Function: Controls substance movement and, in many bacteria, contains the electron transport chain used to generate ATP.

Cytoplasm

Structure: An aqueous mixture containing enzymes, ribosomes, ions, metabolites and genetic material.

Function: Supports metabolic reactions and the synthesis of cellular components required for bacterial growth and reproduction.

Circular DNA

Structure: Usually a circular, double-stranded DNA molecule located in the nucleoid.

Function: Contains essential genes that provide instructions for protein synthesis and regulate bacterial activities.

Plasmids

Structure: Small DNA molecules that replicate independently of the main chromosome.

Function: Carry additional genes that may provide advantages, such as antibiotic resistance or the ability to metabolise particular substances.

Flagellum

Structure: A filament connected to a hook and a rotary basal motor.

Function: Rotates to propel the bacterium through liquid environments, helping it move towards favourable conditions.

Slime Capsule

Structure: An external coating commonly composed of polysaccharides.

Function: Can prevent desiccation, promote attachment to surfaces and protect bacteria against some host immune responses.

Nucleolus

Structure: A dense, non-membrane-bound region inside the nucleus, composed mainly of ribosomal RNA (rRNA), DNA and proteins.

Function: Produces rRNA and assembles ribosomal subunits, which are transported through nuclear pores into the cytoplasm, where they combine to form functional ribosomes for protein synthesis.

Nuclear envelope

Structure: A double membrane containing nuclear pore complexes.

Function: Separates nuclear contents from the cytoplasm and regulates the movement of RNA and proteins between these compartments.

Cristae

Structure: Folds of the inner mitochondrial membrane.

Function: Increase the surface area available for respiratory proteins and ATP synthase, supporting efficient ATP production.

Mitochondrial matrix

Structure: The compartment enclosed by the inner mitochondrial membrane.

Function: Contains enzymes for the citric acid cycle, which generates electron carriers used in oxidative phosphorylation.

Chlorophyll

Structure: A light-absorbing pigment associated with photosystems in thylakoid membranes.

Function: Absorbs light energy and helps drive the photochemical reactions of photosynthesis.

Thylakoids

Structure: Flattened membrane-bound sacs inside chloroplasts.

Function: Contain photosystems and electron transport proteins that generate ATP and NADPH during the light-dependent reactions.

Grana

Structure: Stacks of thylakoids within chloroplasts.

Function: Organise photosynthetic membranes and their protein complexes to support light-dependent reactions.

Stroma

Structure: The fluid-filled compartment inside the chloroplast's inner membrane.

Function: Contains enzymes for the Calvin cycle, which uses ATP and NADPH to incorporate carbon dioxide into organic molecules.

Cell sap

Structure: An aqueous solution containing dissolved sugars, ions, organic acids and other substances inside the vacuole.

Function: Helps regulate water potential, store nutrients and maintain the osmotic balance of the plant cell.