2.02-2.06B Cells

Cell

The smallest structural/functional unit of life (cells themselves are considered living organisms) that constitutes living organisms.

Cell Theory

Scientific theory stating that all living organisms are made of cells. Below are its principles:


1. The cell is the fundamental unit of structure and function in living things.
2. All organisms are made of 1 or more cells.
3. Cells arise from other cells during cellular division.
4. Cells carry genetic material passed to daughter cells during cellular division.
5. All cells are essentially the same in terms of chemical composition.
6. Energy flow (metabolism and biochemistry) occurs within cells.

Animal cells

Eukaryotic cell that’s the basic structural and functional unit of animals.

Plasma membrane

Selectively-permeable organelle that controls what leaves/enters the cell, forming a barrier between intra- and extra- cellular environments. It is a lipid bilayer (2 molecules thick).

Cytoplasm

A jelly-like fluid inside the cell containing water, in which the organelles are suspended and all cellular chemical reactions occur.

Microtubule

Microscopic, hollow tubes constituting the cell’s cytoskeleton.

Cytoskeleton

Microscopic network of protein filaments and tubules in the cytoplasm that helps maintain the cell shape as well as internal organization. Centrosome

Centrosome

Organelle near the nucleus that divides and moves to opposite poles of the cell during mitosis.

Centriole

Microtubule unit constituting the centrosome, it’s responsible for forming spindle fibres in cell division.

Spindle fibres

Protein structures that divides a cell’s genetic material.

Mitosis

Cellular division resulting in 2 daughter cells identical to each other and the parent cell.

Microfilament

Narrow tube-like protein structure involved in cytoplasmic movement and changes in cell shape, it can support/change cell shape by forming a band underneath the plasma membrane.

Lysosome

A vesicle containing digestive enzymes for decomposing excess or worn-out organelles, destroying invading viruses/bacteria, or decomposing carbohydrates/proteins/lipids into smaller units for reusing.

Vesicle

Spheres bounded by membranes that isolate their content from the cytoplasm, used extensively for cell metabolism and transport of large molecules that cannot independently permeate the membrane into the cell.

Vacuole (in animal cells)

A vesicle, in animal cells, they’re small and mainly used for sequestering (isolate or hide away) waste products. They’re temporarily present in animal cells.

Secretory vesicles

Vesicles that secrete waste or materials like hormones and neurotransmitters from the cell. Material is packaged in secretory vesicles at the Golgi Apparatus, then transported to the cell surface for release at the plasma membrane.

Peroxisome

Organelle containing digestive enzymes to decompose toxic cellular material and oxidative enzymes for metabolic activities.

Oxidative enzymes

Enzymes/catalysts for oxidation (chemical combination with oxygen).

Golgi Apparatus

Organelle where proteins received from the endoplasmic reticulum are processed, sorted, modified, packaged, and transported in vesicles for delivery to their destinations (which may be lysosomes, the plasma membrane, or secretion).

Golgi vesicle

Vesicle delivering proteins and lipids from the Golgi Apparatus to their target destination.

Nuclear membrane

Separates the nucleus from the cytoplasm, it has pores to allow some molecules to enter/exit.

Nucleus

“Control center" of the cell containing DNA, chromosomes and RNA, it's responsible for regulating what genes are activated in the cell and when.

Nucleolus

Made from RNA and proteins, site of ribosome synthesis.

Chromosome

A threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

Chromatin

DNA wrapped around histones, chromatin coils together to form chromosomes.

Histones

Basic globular proteins found in chromatin that assist DNA packaging in eukaryotes, structural protein that helps form chromosomes.

DNA

Deoxyribonucleic acid, molecule inside cells that contains the genetic information responsible for the development and function of an organism.

RNA

Ribonucleic acid, single-stranded nucleic acid that passes along genetic messages for protein production.

Smooth endoplasmic reticulum

Network of flattened, membrane-bound sacs without ribosomes studded on them, they’re responsible for synthesizing lipids and removing toxic substances.

Rough endoplasmic reticulum

Involved in the production, processing, and transport of proteins that have been synthesized by ribosomes. It’s a network of flattened, membrane-bound sacs and is called “rough” as it has ribosomes attached onto it.

Ribosomes

Organelle made from both RNA and protein, it’s the site of protein synthesis.

Intermediate filament

Stable structures forming the cells “skeleton”, they position/stabilize the nucleus and give the cell elastic properties to withstand tension.

Mitochondria

The cell’s powerhouse, it’s the site of respiration, found in all living cells. Cells requiring a lot of energy (e.g. myocytes) have many mitochondria to facilitate higher levels of energy production.

Plant cells

Eukaryotic cell that’s the basic structural and functional unit of plants.

Cell sap

Dilute fluid consisting of water, salts, glucose, and amino acids in a plant cell's permanent vacuole

Plant cell wall

Made from cellulose (insoluble carbohydrate), it’s a rigid material that helps plant cells maintain a fixed shape whilst preventing them from bursting (plant cells absorb water which produces an internal pressures that pushes against adjacent cell walls). the cell wall is freely permeable because it has pores allowing water and dissolved substances to leave or enter.

Freely permeable

Any substances can pass through the membrane/surface.

Plasmodesmata

Pores in plant cell walls from which microscopic channels can be formed by allowing a narrow thread of cytoplasm to pass through the cell walls of adjacent plant cells and enable intercellular communication and/or molecular exchange.

Large central vacuole

Large central space surrounded by the tonoplast. The vacuole, unlike animal vacuoles, is much larger, and it’s permanent. It stores cell sap containing water, metabolites, nutrients, sugars, mineral ions, etc. This is a crucial energy store for plant cells, as they cannot move to get their food.

Tonoplast

Vacuole’s membrane.

Chloroplast

Site of photosynthesis, contains a green pigment called chlorophyll, which absorbs light energy to facilitate plants’ photosynthetic processes. Non-green parts of a plant lack chloroplasts and chlorophyll.

Raphide crystal

Needle-like crystals that produce chemicals which damage neck tissue of plant predators when they nibble the plant.

Druse crystal

Stores plants’ excess calcium as calcium oxalate, this is thought to deter herbivory (plant consumption) as high calcium oxalate content is poisonous to humans and animals. Unlike raphides, they are cluster crystals and are roughly spherical aggregates of crystals.

Amyloplast

Plastic that synthesizes and stores starch.

Plastid

Cytoplasmic organelles specific to plants or photosynthetic organisms

Organelle

Specialized structures performing various jobs inside cells. They are difficult to spot under ordinary light microscopes, but electron microscopes can show the details of these structures.

Cells lacking a nucleus are either … (e.g. xylem vessels in a plant’s stem) or don’t … long (e.g. red blood cells).

dead, live

Animal cells and plant cells (both eukaryotes) both have ...

Plasma membrane, cytoplasm, nucleus, nucleolus, chromatin, smooth and rough endoplasmic reticulum, ribosomes, vacuole, mitochondria, golgi apparatus, peroxisome, microtubules, microfilament, secretory vesicles, lysosomes (uncommon in plant cells), intermediate filament,

ONLY animal cells have these organelles ...

Centriole, centrosome, lysosome (usually the case as lysosomes are uncommon in plant cells), sometimes cilia and flagella.

ONLY plant cells have these organelles (because these are required for them to fulfill their autotrophic requirements of conducting photosynthesis whereas animal cells don't need these organelles since they are heterotrophic) ...

Chloroplast, chlorophyll, cellulose cell wall, plasmodesmata, amyloplast, raphide crystal, and druse crystal.

Autotroph

Organisms that can produce their own energy sources through processes such as photosynthesis, chemosynthesis, etc.

Heterotroph

Organism which cannot produce its own food and relies on consumption of other organisms to obtain energy sources.

Plant cells can make their own food so they are ... but animal cells cannot so they are ...

autotroph, heterotroph

Plant cell VS Animal cell - Vacuoles

Plants have ONE large, permanent, vacuole but animal cells have MULTIPLE (if any vacuoles are present) small, temporary vacuoles.

Plant cell VS Animal cell - Shape

Plant cells have fixed, regular shapes because their cell walls create a rigid structure but animal cells are amorphous (have no clearly defined shape/form).

Plant cell VS Animal cell - Size

Plant cells are generally larger than animal cells.

Plant cell VS Animal cell - Food storage

Plant cells store excess glucose/food as starch, animal cells store excess glucose/food as glycogen.

Plant cell VS Animal cell - Mitochondria

Plant cells have less mitochondria as they don’t move as much so require less energy, animal cells have more mitochondria as they move more so require more energy.

Glycogen

Energy source made up of many connected glucose molecules, form of energy storage in animal cells.

Starch

A storage polysaccharide in plants consisting entirely of glucose.

Polysaccharides

Carbohydrates comprised from multiple monosaccharides.

Disaccharides

Carbohydrates that are made up of two monosaccharides.

Monosaccharides

Singular sugar molecules.

Eukaryotes VS Prokaryotes - Cellular Size

Eukaryotes are larger than prokaryotes.

Eukaryotes VS Prokaryotes - Nucleus

Eukaryotes have a membrane-bound nucleus, prokaryotes have an exposed nucleoid region and plasmids instead.

Eukaryotes VS Prokaryotes - DNA

Eukaryotes have linear DNA, prokaryotes have circular DNA.

Eukaryotes VS Prokaryotes - Histones

Basic globular proteins found in chromatin that assist DNA packaging in eukaryotes.

Eukaryotes VS Prokaryotes - Organelles

Eukaryotes have membrane-bound organelles, prokaryotes have no membrane-bound organelles except for their ribosomes.

Eukaryotes VS Prokaryotes - Ribosomes

Both eukaryotes and prokaryotes have ribosomes.

Eukaryotes VS Prokaryotes - Number of cells

Eukaryotes can be both multicellular and unicellular, prokaryotes are unicellular.

Eukaryotes VS Prokaryotes - Cell wall material

Eukaryotes normally do not have a cell wall, if they do (as in plants and fungi), it's made of cellulose. Prokaryotes have a cell wall made of peptidoglycan or mucopeptide.

Eukaryotes VS Prokaryotes - Mitochondria

Eukaryotes have mitochondria, prokaryotes don't.

Eukaryotes VS Prokaryotes - Chloroplasts

Some eukaryotes (plants and algae) have chloroplasts, prokaryotes do not have chloroplasts, instead their chlorophyll is scattered in the cytoplasm.

Eukaryotes VS Prokaryotes - Endoplasmic Reticulum

Eukaryotes have endoplasmic reticulum, prokaryotes do not.

Eukaryotes VS Prokaryotes - Golgi Apparatus

Eukaryotes have golgi apparatus, prokaryotes do not.

Eukaryotes VS Prokaryotes - Lysosomes

Eukaryotes have lysosomes, prokaryotes do not.

Eukaryotes VS Prokaryotes - Peroxisomes

Eukaryotes have peroxisomes, prokaryotes do not.

Eukaryotes VS Prokaryotes - Mesosome

Plasma membrane in bacteria that folds into the cytoplasm and increases surface area. Eukaryotes do not have this, but prokaryotes do.

Eukaryotes VS Prokaryotes - Centrosome

Eukaryotes have centrosomes, prokaryotes do not.

Eukaryotes VS Prokaryotes - Cilia

Eukaryotes have cilia, prokaryotes do not.

Eukaryotes VS Prokaryotes - Reproduction (sexual/asexual)

Eukaryotes mostly reproduce sexually, prokaryotes can reproduce both sexually and asexually.

Sexual reproduction

Reproduction where cells from two parents unite to form the first cell of a new organism

Asexual reproduction

Reproduction where only one parent produces offspring that are identical to the parent.

Eukaryotes VS Prokaryotes - Cell division

Eukaryotes do cell division by mitosis. Prokaryotes do cell division asexually by binary fission and sexually by conjugation as well as other methods.

Eukaryotes VS Prokaryotes - Metabolic rate

Eukaryotes have lower metabolic rates than prokaryotes.

REukaryotes VS Prokaryotes - espiration

Eukaryotes respire with their mitochondria, prokaryotes do so with their cytoplasm and/or plasma membrane.

Eukaryotes VS Prokaryotes - DNA Replication

Eukaryotes replicate DNA in their nucleus, prokaryotes do this in their cytoplasm.

Eukaryotes VS Prokaryotes - Glycocalyx

Eukaryotes without cell walls have glycocalyx, prokaryotes have it in their capsule or slime layer.

No matter what cell type, all cells have these 3 things in common:

cell membrane, cytoplasm, and DNA or other form of genetic material.

Mitosis

Cell division resulting in 2 daughter cells identical to the parent cell:


1. Chromatin in the nucleus condenses and coils into chromosomes.
2. All chromosomes in the nucleus are copied.
3. The nucleus splits into 2 equal parts, each containing the same number and type of chromosomes.
4. The cell’s cytoplasm divides into 2 (in plant cells a new cell wall also forms) to form 2 smaller identical cells.


1. The 2 genetically-identical daughter cells ingest food substances to supply energy and building materials to enable them to grow to their full size.

Specialized cells

Cells adapted to perform specific functions that benefit the entire multicellular organism. E.g. nerve cells, red blood cells, smooth muscle cells, adipose cells, intestinal epithelial cells, striated muscle cell, bone tissue with osteocytes, loose connective tissue, fibroblasts, etc.

The sperm has a … for swimming and its ….. contains …..

tail, head, father genes

Adaptation

A characteristic that improves an individual's ability to survive and reproduce in a particular environment.

Stem Cell

Unspecialized cells possessing the potential to specialize. They are used when signalled by the body to facilitate growth, reproduction, repair, etc.

Differentiation

Irreversible process where stem cells become specialized by activating some parts of their nucleus' DNA and de-activating components irrelevant to their planned specialized function.

Stem cells divide by ...

mitosis

Self-renewal of stem cells

When stem cells undergo numerous mitotic divisions while maintaining an undifferentiated state.

Gestation

Period from fertilization of the ovum to birth

Embryo

Developing human organism from 2nd to 8th week in gestation.

Zygote

Fertilized egg, totipotent singular cell formed by fusing the ovum and sperm for reproduction. Multicellular eukaryotes such as plants and animals begin life as a zygote. The zygote then divides into 2, 4, 8 cells, etc, mitotically.