BIOLOGY YEAR 10 TERM 1+2 REVISION

Cells

The building blocks of life

Homeostasis

Homeostasis is a self-regulating process that allows organisms to maintain internal stability while adjusting to conditions optimal for survival.

Membranes

Biological membranes are structures that separate cells from their environment and organelles from one another, regulating the passage of substances in and out.

Phospholipids

Building blocks of the plasma membrane, phospholipids form a bilayer with hydrophilic (water-attracting) heads, faced outwards and hydrophobic (water-repelling) tails facing into the cell. This forms a semi-permeable membrane to control substances moving in and out of the cell

What can easily enter a cell?

Small, nonpolar molecules like oxygen and carbon dioxide.

What needs extra help to enter a cell?

Large, polar (glucose and amino acids), Ions (potassium and sodium)

Fluid Mosaic Model/Fluid mosaic phospholipid bilayer model

The structure of a cell membrane contains 2 layers of phospholipids, known as a phospholipid bilayer.

Proteins

Various proteins embed (integral) or attach (peripheral) to the phospholipid bilayer. They play crucial roles in transport of substances, signalling and cell recognition

Peripheral Proteins

Peripheral proteins are a group of biologically active molecules formed from amino acids which interact with the surface of the lipid bilayer of cell membrane.

Integral Proteins

Integral proteins are embedded within (and often extend across) the phospholipid bilayer of cell membranes. Their functions include facilitating communication and transport across the membrane, acting as channels or transporters for molecules, and playing roles in cell signaling.

Cholesterol

Cholesterol molecules are positioned among the phospholipids. helping to maintain membrane fluidity. They prevent fatty chains of the phospholipids from packing too close together so the flexibility and structure of the membrane survive changes in temperature.

Carbohydrates

Carbohydrates are often attached to proteins (forming glycoproteins) or lipids (forming glycolipids) on the extracellular surface of the membrane. They are involved in cell recognition and communication, playing a vital role in immune response and tissue formation.

Functions of the cell membrane

Selective permeability, Cell Communication, Fluidity and Flexibility

Selective permeability

The fluid mosaic model explains how the plasma membrane selectively allows certain substances to pass while blocking others, maintaining the internal environment of the cell

Cell Communication

Membrane proteins assist communication between the cells and their external environment, allowing for signal transduction and responses to external stimuli.

Fluidity and Flexibility

These characteristics allow the membrane to change shape, move and interact with their environment more effectively.

Enzymes

Enzymes are biological catalysts made up of proteins. The main function is to speed up biochemical reactions of substrates in cells and reduce energy needed for such reactions (for survival).

Lock and key model

The enzyme’s active site has a fixed shape that perfectly fits the substrate.

Induced fit model

The enzyme’s active site changes shape slightly to fit the substrate more closely during the reaction.

Diffusion

The process of diffusion across a cell membrane is when water from a high water concentration gradient to a low water concentration gradient.

Osmosis

The diffusion of water along a concentration gradient from an area of low solute concentration to an area of high solute concentration across a semi-permeable membrane

Hypertonic

Hypertonic refers to when a cell has ‘high solute levels and low solvent, causing water to disperse and forces osmosis in the cell, causing the cell to shrivel.

Hypotonic

Hypotonic refers to when a cell is placed in a hypotonic solution, it will gain water and expands to become turgid

Isotonic

Isonic refers to when solute levels remain the same, equal and stable.

Function of the cardiovascular system

The function of the cardiovascular system is to deliver oxygen, nutrients and hormones to target cells (transportation) and remove waste.

Structures of the cardiovascular system

The system is made up of the main components being: blood vessels, arteries, veins and capillaries.

Function of blood vessels

The blood vessels carry blood around the body delivering various substances to cells

What direction do the blood vessels move?

Blood that moves away from the heart travels in arteries

Blood that move toward the heart travels in veins

What do arteries have?

Arteries have muscular walls to push blood.

What do veins contain?

Veins contain valves to stop moving blood backwards.

What are capillaries responsible for?

Capillaries are responsible for the transportation of substances from the blood into the cell across the cell membrane (diffusion).

Blood pressure

Blood pressure is needed to keep the blood moving through the cardiovascular system.

What is the purpose of the respiratory system?

The purpose of the respiratory system is gaseous exchange. This means the exchange of oxygen into the blood and removal of carbon dioxide from the blood through the alveoli

Function of the nervous system

To control, regulate and provide a communication system in the body using electrical and chemical signals.

Central Nervous System (CNS)

The core of the nervous system, consisting of the brain, spinal cord and relay neurons (interneurons)

Peripheral Nervous System (PNS)

Consists of all other nerves around the body, including cranial nerves, spinal nerves, sensory neurons and motor neurons.

Neuron

The scientific term for nerve cells

Cerebrum

The largest part of the brain. It is responsible for muscle movements, posture and balance.

Cerebellum

Looks like a ‘mini brain’ located under the cerebrum; it is responsible for muscle movements, posture and balance.

Brain stem

The structure that connects the rest of the brain to the spine. It controls vital involuntary functions like breathing, heart rate, body temperature, sleep, digestion, sneezing and swallowing.

Stimulus

An event or change in the environment that triggers a response

Receptor

The part of the body (like the eye or skin) that receives the stimulus

Sensory Neuron

Neurons acting as receptors that send information about the stimulus to the Central Nervous System

Relay Neuron

Neurons found within the CNS that transport information from the spinal cord to the brain for processing and then back to the spinal cord

Motor Neuron

Neurons that receive instructions from relay neurons and carry out the physical effect or response

Effector

The muscle that carries out the final physical response to the original stimulus

Sensory-Motor Pathway

The complete step by step process of communication (Stimulus → Sensory Neuron → CNS → Motor Neuron → Effector), which takes about 0.28 seconds on average

Reflex Arc

A rapid pathway that skips the brain’s conscious processing stage to drastically reduce the time between a stimulus and an effect. Evolutionarily, this is designed for survival and self-preservation.

What is the main function of the male reproductive system?

To produce, maintain and transport sperm for fertilisation.

What steps are involved in sperm production?

1.Sperm is made - Stored in the epididymis while inactive

2.The sperm travels through the Vas Deferens to the Urethra

3.Nutrition is provided - The seminal vesicles add nutritive sugar which activate the sperm to swim

4.The sperm moves to the prostate gland - Mixes with acidic solution now called semen

5.Ejaculation from penis

What is the primary function of the seminal vesicles?

The seminal vesicles adds nutritive sugar to provide energy and activates sperm to swim.

Urethra and penis

The urethra is a canal approximately 20cm long through which both urine and semen leave the body

The tip of the penis is called the glans.

Ovary

Two ovaries which are glands approximately the size of grapes/almonds

Bladder

An organ in the female reproductive system that stores urine before it is expelled from the body.

Uterus

Duct which transports urine from the bladder to the exterior - approx 4cm long.

Clitoris

Sensitive mass of erectile tissue above urethral opening which assists in successful reproduction

Oviduct

The oviduct, also known as the fallopian tube, is a pair of slender tubes in the female reproductive system that transport eggs from the ovaries to the uterus. It is also the site where fertilization of the egg by sperm usually occurs.

Endometrium

Inner lining of uterus, under the influence of female hormones oestrogen and progesterone, sheds each month.

Cervix

The cervix is the lower part of the uterus that opens into the vagina. It serves as a passageway for menstrual fluid to exit the body, a canal for sperm to enter the uterus, and it dilates during childbirth to allow the baby to pass through.

Vagina

The vagina is a muscular canal in the female reproductive system that connects the external genitalia to the uterus, facilitating sexual intercourse, childbirth, and menstrual flow.

Labium majora/minora

External genitals that cover and provide protection for the vaginal and urethral openings.

What are the four phases of the menstrual cycle?

1.Menstrual Phase days 1-7

2.Follicular phase days 1-13

3.Ovulation phase day 14

4.Luteal Phase days 15-28

What hormones are involved in the menstrual cycle?

FSH secreted by the pituitary gland - Menstruation

FSH secreted by the pituitary gland - Follicular Phase

Oestrogen secreted by the ovary - Follicular phase

LH secreted by the pituitary gland - Ovulation

Progesterone and Oestrogen secreted by the ovary - Luteal Phase

What is DNA?

DNA is the molecule that carries genetic information in living organisms.

Where is DNA found?

DNA is mainly found in the nucleus of cells and is arranged into structures called chromosomes.

What are the sides of DNA made from?

Sugar and phosphate molecules

What shape is DNA in?

DNA has a double helix shape which looks like a twisted ladder.

What do genomes contain?

Genomes contain all of the DNA, including every gene and non-coding sequence found in its cells. It contains all the instructions needed for an organism to grow, develop, function and reproduce.

What does the DNA pairing rule state?

The DNA pairing rule states that certain bases can only pair with each other.

What are the DNA pairings?

(A)denine ←> (T)hymine

(C)ytosine ←> (G)uanine

Apples in the trees (A pairs with T)

Cars in the Garage (C pairs with G)

How do channel proteins assist particle transport?

Channel Proteins assist particle transport by allowing inorganic ions to pass through the membrane

What do carrier proteins transport across the cell membrane and how do they do it?

Carrier proteins allow large lipid-insoluble molecules that cannot cross the membrane by simple diffusion to be transported into the cell.

What process is responsible for gas exchange in the lungs?

Gas exchange in the lungs occurs primarily through diffusion across the alveolar-capillary membrane, allowing oxygen to enter the blood and carbon dioxide to be expelled.

What substance is transported by osmosis?

The substance that is transported by osmosis is water. Osmosis is the movement of water molecules across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration.

What are carrier channels made of in the phospholipid bilayer?

Carrier channels in the phospholipid bilayer are primarily composed of integral proteins that form a pore or channel through the bilayer.

What are chromosomes?

Each human is made up of 46 pieces of DNA condensed into chromosomes. These chromosomes are found in pairs, making 23 pairs. Each pair of chromosomes contains one chromosome that has been inherited (given) from each parent.

What are genes?

A gene is a unit of hereditary information.

Phenotype

The physical traits of an organism (i.e.what it looks like).

Genotype

An organism's genetic makeup—the specific alleles it has for a gene

Allele

An allele is a specific variant of a gene that can produce different traits.

Homozygous

Also known as pure breeding. When an individual has two identical alleles on each chromosome

Heterozygous

When an individual has a different allele on each chromosome

Wild Type

Refers to the most common phenotype for a characteristic in a population

Homozygous dominant

Both alleles are dominant, dominant trait is shown

Homozygous recessive

Both alleles are recessive, recessive trait is shown

Genome

The genome is the complete set of genetic material in an organism - It includes all of the DNA, including every gene and non-coding sequence, found in its cells.

Mitosis

A type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth.

Meiosis

Meiosis is a specialized type of cell division that produces four genetically distinct haploid gametes from a diploid parent cell, essential for sexual reproduction.