Cell Biology and Enzyme Function Overview

Prokaryotic Cells

Cells without a true nucleus; DNA is located in a nucleoid.

Eukaryotic Cells

Cells with a true nucleus that is membrane-bound.

Nucleus

The control center of the cell, containing DNA and directing all cellular activities.

DNA Structure

Single, circular chromosome in prokaryotic cells; multiple, linear chromosomes in eukaryotic cells.

Cell Membrane

A lipid bilayer that controls the movement of substances in and out.

Cytoplasm

The fluid where cellular activities occur.

Ribosomes

Small structures that synthesize proteins.

Metabolism

The set of chemical reactions that sustain life.

Mitochondria

Powerhouse of the cell, generating ATP (energy) through cellular respiration.

Endoplasmic Reticulum (ER)

Processes and transports proteins & lipids.

Golgi Apparatus

Modifies, packages, and ships proteins and lipids.

Lysosomes

Contain digestive enzymes to break down waste and cellular debris.

Cytoskeleton

Provides structural support and helps in cell movement.

Chloroplasts

Carry out photosynthesis to produce energy in plant cells.

Centrioles

Assist in cell division (mitosis) in animal cells.

Vacuoles

Store nutrients, water, and waste; large central vacuole in plant cells.

Cell Specialisation

The process by which cells develop unique structures and functions.

Differentiation

The process by which unspecialised cells become specialised.

Stem Cells

Undifferentiated cells that have the potential to develop into different cell types.

Cell Division in Eukaryotic Cells

Mitosis and meiosis.

Tissue

A group of similar specialised cells working together to perform a function.

Organ

A collection of tissues that work together to perform a specific function.

Muscle Cells

Specialised cells that contract to enable movement.

Nerve Cells

Cells that transmit electrical signals throughout the body.

Red Blood Cells

Cells adapted to carry oxygen using haemoglobin and having a biconcave shape for increased surface area.

Root Hair Cells

Plant cells with elongated extensions to absorb water and minerals efficiently.

Xylem Cells

Hollow, tube-like plant cells that transport water and minerals.

Phloem Cells

Plant cells that transport sugars and nutrients throughout the plant.

Cell Potency

Refers to a cell's ability to differentiate into different cell types. The greater the potency, the more types of cells it can become.

Totipotent

Can differentiate into any cell type, including embryonic and extra-embryonic (placenta) cells. Example: Zygote (fertilised egg).

Pluripotent

Can differentiate into any cell type in the body but not extra-embryonic cells. Example: Embryonic stem cells.

Multipotent

Can differentiate into a limited range of cells within a specific tissue. Example: Adult stem cells in bone marrow (can become red/white blood cells).

Unipotent

Can only develop into one specific cell type. Example: Muscle stem cells forming muscle fibers.

Embryonic Stem Cells

Found in early embryos and are pluripotent, meaning they can develop into almost any cell type.

Adult (Somatic) Stem Cells

Found in specific tissues (e.g., bone marrow) and are multipotent, meaning they can only become a limited range of cells.

Induced Pluripotent Stem Cells (iPSCs)

Adult cells that have been genetically reprogrammed to behave like pluripotent stem cells.

Perinatal Stem Cells

Found in umbilical cord blood and amniotic fluid; they have multipotent capabilities and can be used in medical treatments.

Active Transport

The movement of molecules or ions across a cell membrane against their concentration gradient (from low to high concentration) using energy (ATP).

Difference from Passive Transport

Unlike passive transport (diffusion, osmosis, facilitated diffusion), active transport requires energy because it moves substances against the natural concentration gradient.

ATP

Energy-carrying molecule used to power active transport.

Concentration gradient

Difference in the concentration of a substance across a membrane.

Sodium-Potassium Pump (Na+/K+ Pump)

Moves Na+ out and K+ into the cell, crucial for nerve signaling.

Carrier protein

A membrane protein that transports substances across the cell membrane.

Endocytosis

Process where a cell engulfs materials into vesicles for transport into the cell.

Exocytosis

Process where vesicles fuse with the membrane to release substances out of the cell.

Phagocytosis

Type of endocytosis where the cell engulfs solid particles.

Pinocytosis

Type of endocytosis where the cell engulfs liquid particles.

Homeostasis

The process of maintaining a stable internal environment in the cell.

Active Transport

Movement of substances against their concentration gradients using ATP.

Bulk Transport

The process by which large molecules, particles, or fluids move across the cell membrane using energy (ATP).

Simple Diffusion

Movement of molecules from high to low concentration (down the concentration gradient) without energy.

Osmosis

Movement of water molecules from high to low water potential across a semi-permeable membrane.

Permeability

The ability of a membrane to allow certain substances to pass through while blocking others.

Selectively Permeable

A membrane that permits some molecules (e.g., water, gases) to pass while restricting others.

Solvent

A substance, like water, that dissolves solutes to form a solution.

Receptor-mediated endocytosis

The cell selectively engulfs specific molecules using receptor proteins.

Facilitated Diffusion

Movement of molecules from high to low concentration with the help of channel/carrier proteins.

Example of Simple Diffusion

Oxygen moving into cells.

facilitated diffusion (passive)

Glucose entering cells through carrier proteins.

Osmosis

Water moving into plant root cells.

Phagocytosis

White blood cells engulfing bacteria.

Example of Pinocytosis

The cell takes in extracellular fluids and dissolved substances.

Solute

A substance that dissolves in a solvent, such as salt or sugar in water.

Osmosis

Water moves across a selectively permeable membrane to balance solute concentrations.

Hypertonic Solution

Higher solute concentration outside the cell than inside, causing water to leave the cell, resulting in shrinkage.

Isotonic Solution

No net water movement; the cell remains the same size with equal solute concentration inside and outside the cell.

Hypotonic Solution

Lower solute concentration outside the cell than inside, causing water to enter the cell, which may lead to swelling or bursting.

Crenation

The shrinkage of animal cells due to loss of water in a hypertonic solution.

Plasmolysis

The shrinkage of plant cells due to loss of water in a hypertonic solution.

Turgid

The state of a plant cell when it is swollen due to water entering in a hypotonic solution.

Stages of Digestion

Ingestion, mechanical digestion, and chemical digestion.

Mouth

Function: Food is chewed and mixed with saliva, starting the digestion process.

Oesophagus

Role: A muscular tube that transports food from the mouth to the stomach.

Stomach

Stages of Digestion: Mechanical digestion (churning) and chemical digestion (enzymes and acid).

Duodenum

The first part of the small intestine where chemical digestion occurs.

Sodium Bicarbonate

Neutralizes stomach acid to prevent damage to the duodenum.

Hydrochloric Acid (HCl)

Lowers pH to create an acidic environment in the stomach.

Bile Salts

Break down fats into smaller droplets for enzyme action.

Protease (Pepsin)

Secreted by chief cells, pepsin breaks down proteins into peptides and is only active at a pH of 2-3.

Role of Enzymes

Break down proteins, fats, and carbohydrates into absorbable molecules.

Role of Saliva

Salivary glands produce saliva, which contains enzymes like amylase that begin breaking down carbohydrates.

Chyme

The semi-liquid mixture of partially digested food and digestive juices.

Pyloric Sphincter

A smooth muscle that controls the release of chyme into the duodenum.

Large Intestine

Absorption of water and elimination of waste.

Bile

Aided chemical digestion by producing bile.

Lipase

Breaks down fats with the help of bile.

Bile Salts

Help digest fats and remove toxins.

Jejunum and Ileum

Parts of the small intestine involved in nutrient absorption.

Protease

Digests proteins into amino acids.

Amylase

Converts starch into simple sugars.

Beneficial Bacteria

Help digest fiber, produce vitamins (e.g., vitamin K, B12), and maintain gut health.

Epithelial Cells

Lined with villi and microvilli, which increase surface area for nutrient absorption.

Pancreatic Duct Blockage

Prevents enzyme release, leading to malabsorption and CF-related diabetes (CFRD).

Vitamin K Deficiency

Fat absorption decreases, leading to deficiencies in fat-soluble vitamins, including vitamin K.

Water Absorption

Extracts water from waste to form solid feces; cholera causes excessive water loss through diarrhea.

Main Contents of Feces

Water, undigested fiber, dead bacteria, and waste products.

Crohn's Disease

A chronic inflammation of the intestines that leads to malabsorption, diarrhea, and nutrient deficiencies.

Enzyme Inhibitors

Substances that disrupt enzyme function.

Active Site

The specific region of an enzyme where a substrate binds.

Phenylketonuria (PKU)

Genetic disorder caused by a mutation in the gene for phenylalanine hydroxylase (PheOH).