Cell Structure, Function, and Processes in Biology: Paramecium, Cell Theory, Transport, and Reproduction

How does a paramecium carry out excretion?

Plasma membrane controls entry/exit of substances, expelling metabolic waste.

What structure allows a paramecium to move?

Cilia.

Where does a paramecium store and digest food it has consumed?

Food vacuoles.

How does a paramecium grow?

By consuming and assimilating biomass until it divides.

How does a paramecium reproduce?

Mostly asexual reproduction via mitosis (nucleus divides).

How does a paramecium maintain homeostasis?

Contractile vacuole expels excess water through plasma membrane.

What are the three main points of cell theory?

1) All living things are made of one or more cells. 2) The cell is the basic structural & functional unit of life. 3) Cells arise from pre-existing cells by cell division.

What is the smallest independent unit of life?

The cell.

Why can't organelles survive alone?

They're specialised structures that rely on the cell for survival.

What is always present in every cell type and defines its boundary?

Cell membrane.

What is the thickness of the cell membrane?

~8 nanometres.

What is the cell membrane mainly made of?

Lipids and proteins (phospholipid bilayer).

What role does cholesterol play in the cell membrane?

Regulates fluidity (keeps it flexible at low temps, stable at high temps).

Which part of the phospholipid is hydrophilic?

The head (faces outwards).

Which part of the phospholipid is hydrophobic?

The tail (faces inwards).

What factors influence substance movement across membranes?

Size, charge, and solubility.

Which cell type evolved first?

Prokaryotic cells.

Do prokaryotic cells have a nucleus?

No, they lack a nucleus.

What size range are prokaryotic cells?

0.1 - 10 μm.

What are common structures found in prokaryotes?

Capsule, pili, flagella.

What is the main feature of eukaryotic cells?

They have a nucleus with linear chromosomes and membrane-bound organelles.

What does the nucleolus do?

Makes ribosomes.

What is the function of mitochondria?

Site of aerobic respiration, produces energy.

What is the function of ribosomes?

Site of protein synthesis.

What is the function of rough ER?

Makes and transports proteins.

What is the function of smooth ER?

Synthesises carbohydrates and lipids.

What is the function of the Golgi body?

Modifies, packages, and secretes proteins.

What is the function of lysosomes?

Contain digestive enzymes for breakdown.

What additional structures do plant cells have?

Cell wall (cellulose), chloroplasts, large vacuole.

What is passive transport?

Movement of molecules without energy input.

What is diffusion?

Movement of molecules from high to low concentration until equilibrium.

What gases move by diffusion?

Oxygen and carbon dioxide.

What is facilitated diffusion?

Passive transport using channel proteins for larger molecules (e.g., glucose).

Diffusion

Diffusion of water across a semi-permeable membrane from low solute concentration to high.

Active transport

Movement of substances against the concentration gradient using energy (ATP) and carrier proteins.

Example of active transport in humans

Glucose uptake in the small intestine; sodium removal in red blood cells.

Example of active transport in plants

Uptake of nitrogen, potassium, and phosphorus from soil.

Endocytosis

Active bulk transport of substances into the cell.

Types of endocytosis

Phagocytosis (solids), pinocytosis (liquids).

Exocytosis

Active transport of substances out of the cell via vesicles.

Chromosome

A length of DNA carrying genetic information.

Chromatid

A replicated chromosome joined to its twin (sister chromatids).

When are chromosomes visible?

During cell division (mitosis).

Interphase

Cell growth, organelle synthesis, DNA replication, error checking.

Mitosis

Chromosomes divide into two identical sets.

Cytokinesis

Cytoplasm divides, forming daughter cells.

Stages of mitosis

Prophase, Metaphase, Anaphase, Telophase.

Prophase

Chromosomes condense, sister chromatids become visible.

Metaphase

Chromosomes align at the equator of the cell.

Anaphase

Spindle fibres pull sister chromatids apart to opposite poles.

Telophase

Chromatids arrive at poles, nuclear envelopes reform.

Prokaryotes division

By binary fission.

Steps of binary fission

1) DNA replication, 2) DNA segregation, 3) Cytokinesis, 4) Daughter cells formed.

Photosynthesis location

In chloroplasts containing chlorophyll.

Word equation for photosynthesis

Carbon dioxide + water → glucose + oxygen.

Chemical equation for photosynthesis

6CO2 + 6H2O → C6H12O6 + 6O2.

Respiration location

Cytoplasm and mitochondria.

Aerobic respiration

Respiration using oxygen, producing lots of ATP.

Anaerobic respiration

Respiration without oxygen, less efficient.

Fermentation

Anaerobic breakdown of glucose in cytoplasm, produces ethanol or lactic acid.

Sour taste in yoghurt and cheese

Lactic acid (produced by bacteria breaking down lactose).

Microorganisms in alcohol production

Yeast and some bacteria (fermentation of sugars).

Gas produced by yeast during bread making

Carbon dioxide (causes dough to rise).

Discovery of penicillin

Alexander Fleming, developed further by Howard Florey and others.

Microorganisms in sewage treatment

Remove nitrogen, phosphorus, and biological contaminants.

Vitamin produced by archaea/bacteria

Vitamin B12.

Vitamin produced by E. coli in large intestine

Vitamin K.